1.
Alluvial diagram
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Alluvial diagrams are a type of flow diagram originally developed to represent changes in network structure over time. In allusion to both their appearance and their emphasis on flow, alluvial diagrams are named after alluvial fans that are naturally formed by the soil deposited from streaming water. In an alluvial diagram, blocks represent clusters of nodes, the height of a block represents the size of the cluster and the height of a stream field represents the size of the components contained in both blocks connected by the stream field. Alluvial diagrams were originally developed to visualize structural change in large complex networks and they can be used to visualize any type of change in group composition between states or over time and include statistical information to reveal significant change. Alluvial diagrams highlight important structural changes that can be emphasized by color. Alluvial diagrams can also be used to illustrate patterns of flow on a network over time. The Users Flow feature of Google Analytics uses alluvial diagrams to represent how visitors move among the nodes on a web sites
2.
Alaska
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Alaska is a U. S. state located in the northwest extremity of North America. To the north are the Chukchi and Beaufort seas–the southern parts of the Arctic Ocean, the Pacific Ocean lies to the south and southwest. Alaska is the largest state in the United States by area, the 3rd least populous, approximately half of Alaskas residents live within the Anchorage metropolitan area. Alaskas economy is dominated by the fishing, natural gas, military bases and tourism are also a significant part of the economy. The United States purchased Alaska from the Russian Empire on March 30,1867, the area went through several administrative changes before becoming organized as a territory on May 11,1912. It was admitted as the 49th state of the U. S. on January 3,1959, the name Alaska was introduced in the Russian colonial period when it was used to refer to the peninsula. It was derived from an Aleut, or Unangam idiom, which refers to the mainland of Alaska. Literally, it means object to which the action of the sea is directed, Alaska is the northernmost and westernmost state in the United States and has the most easterly longitude in the United States because the Aleutian Islands extend into the Eastern Hemisphere. Alaska is the only non-contiguous U. S. state on continental North America and it is technically part of the continental U. S. but is sometimes not included in colloquial use, Alaska is not part of the contiguous U. S. often called the Lower 48. The capital city, Juneau, is situated on the mainland of the North American continent but is not connected by road to the rest of the North American highway system. Alaskas territorial waters touch Russias territorial waters in the Bering Strait, as the Russian Big Diomede Island, Alaska has a longer coastline than all the other U. S. states combined. Alaska is the largest state in the United States by total area at 663,268 square miles, over twice the size of Texas, Alaska is larger than all but 18 sovereign countries. Counting territorial waters, Alaska is larger than the area of the next three largest states, Texas, California, and Montana. It is also larger than the area of the 22 smallest U. S. states. Also referred to as the Panhandle or Inside Passage, this is the region of Alaska closest to the rest of the United States, as such, this was where most of the initial non-indigenous settlement occurred in the years following the Alaska Purchase. The region is dominated by the Alexander Archipelago as well as the Tongass National Forest and it contains the state capital Juneau, the former capital Sitka, and Ketchikan, at one time Alaskas largest city. The Alaska Marine Highway provides a vital transportation link throughout the area. The Interior is the largest region of Alaska, much of it is uninhabited wilderness, Fairbanks is the only large city in the region
3.
Gamtoos River
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Gamtoos River or Gamptoos River is a river in the Eastern Cape Province, South Africa. It is formed by the confluence of the Kouga River and the Groot River and is approximately 645-kilometre long with a catchment area of 34,635 square kilometres, the Gamtoos river system is formed by the Groot, the Kouga and the Baviaanskloof Rivers. The latter is a tributary of the Kouga, although the rainfall in the catchment area is low, it supports a commercial irrigated agriculture in the lower catchment in which oranges, tobacco, citrus fruit and vegetables are grown. There is an estuary where the Gamtoos river enters the Indian Ocean and it is located between Jeffreys Bay and Port Elizabeth and the Gamtoos River Mouth Nature Reserve is in the area. The towns of Hankey, the oldest town situated in the Gamtoos river valley, further inland are the towns of Steytlerville, Joubertina, Uniondale, Willowmore and Murraysburg. Tributaries include the Loerie River, Klein River, Hol River, besides the Groot, saartjie Baartman - the Hottentot Venus - was born around 1789 in the vicinity of the Gamtoos river. In 1877 during a drought in the region, the Gamtoos River dried up completely. During the floods of October 1867, according to John Croumbie Brown, two bridges cross the Gamtoos close to its mouth in the Kouga. The original 180-metre bridge on the R102 was opened in 1895 in order to replace the ferry that had been in use up to that time, a modern concrete bridge was built during the construction of the N2 in the early 1970s. Presently this river is part of the Fish to Tsitsikama Water Management Area, until then it had been thought that its distribution was restricted to the area between the Keurbooms and the Olifants River. List of rivers of South Africa List of estuaries of South Africa Media related to Gamtoos River at Wikimedia Commons Birding - Gamtoos River Mouth IUCN Red List - Galaxias zebratus
4.
South Africa
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South Africa, officially the Republic of South Africa, is the southernmost country in Africa. South Africa is the 25th-largest country in the world by land area and it is the southernmost country on the mainland of the Old World or the Eastern Hemisphere. About 80 percent of South Africans are of Sub-Saharan African ancestry, divided among a variety of ethnic groups speaking different Bantu languages, the remaining population consists of Africas largest communities of European, Asian, and multiracial ancestry. South Africa is a multiethnic society encompassing a variety of cultures, languages. Its pluralistic makeup is reflected in the recognition of 11 official languages. The country is one of the few in Africa never to have had a coup détat, however, the vast majority of black South Africans were not enfranchised until 1994. During the 20th century, the black majority sought to recover its rights from the dominant white minority, with this struggle playing a role in the countrys recent history. The National Party imposed apartheid in 1948, institutionalising previous racial segregation, since 1994, all ethnic and linguistic groups have held political representation in the countrys democracy, which comprises a parliamentary republic and nine provinces. South Africa is often referred to as the Rainbow Nation to describe the multicultural diversity. The World Bank classifies South Africa as an economy. Its economy is the second-largest in Africa, and the 34th-largest in the world, in terms of purchasing power parity, South Africa has the seventh-highest per capita income in Africa. However, poverty and inequality remain widespread, with about a quarter of the population unemployed, nevertheless, South Africa has been identified as a middle power in international affairs, and maintains significant regional influence. The name South Africa is derived from the geographic location at the southern tip of Africa. Upon formation the country was named the Union of South Africa in English, since 1961 the long form name in English has been the Republic of South Africa. In Dutch the country was named Republiek van Zuid-Afrika, replaced in 1983 by the Afrikaans Republiek van Suid-Afrika, since 1994 the Republic has had an official name in each of its 11 official languages. Mzansi, derived from the Xhosa noun umzantsi meaning south, is a name for South Africa. South Africa contains some of the oldest archaeological and human fossil sites in the world, extensive fossil remains have been recovered from a series of caves in Gauteng Province. The area is a UNESCO World Heritage site and has termed the Cradle of Humankind
5.
Alluvial plain
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An alluvial plain is a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms. As the highlands due to weathering and water flow, the sediment from the hills is transported to the lower plain. Various creeks will carry the water further to a river, lake, bay, as the sediments are deposited during flood conditions in the floodplain of a creek, the elevation of the floodplain will be raised. As this reduces the channel capacity, the creek will, over time, seek new, lower paths. These processes, over time, will form the plain. The NCSS glossary instead suggests flood plain
6.
Red Rock Canyon State Park (California)
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Red Rock Canyon State Park features scenic desert cliffs, buttes and spectacular rock formations. The park is located where the southernmost tip of the Sierra Nevada converges with the El Paso Mountains, each tributary canyon is unique, with vivid colors. After wet winters, the floral displays are notable. Wildlife includes roadrunners, hawks, lizards, mice and squirrels, the park is located on State Route 14, which connects U. S. Route 395 with the communities of Southern California, where 14 is known as the Antelope Valley Freeway. The park is 25 miles northeast of Mojave on SR14, SR14 goes through the center of the park, in the canyon itself. It is not far from Cantil, California, camping, picnic, and restroom facilities are available in several sites immediately off of California Route 14. The area was home to the Kawaiisu Indians. Some petroglyphs and pictographs are found in the El Paso mountains, the Coso People were early Native American inhabitants of this locale. The colorful rock formations in the served as landmarks during the early 1870s for 20-mule team freight wagons that stopped for water. The park protects significant paleontology sites and the remains of 1890s-era mining operations, between these two photographs,66 years have elapsed. In the 1933 picture Red Rock Canyon was on U. S. Route 6, the scenery at this point in the road eventually led to the creation of Red Rock Canyon State Park in 1968. A dirt road crosses the center of the view, in the 1999 photo, a total of 17 species are now present in the foreground. No Yuccas, Joshua trees or other plants have persisted over the 66 years between the dates of the photographs, in most of the repeat photography, few Yuccas appear to live longer than about 40 years. Many more plants appear in the 1999 view, partially in response to decreased disturbance as well as increased precipitation in the part of the 20th century. For example, the road that crossed the foreground is difficult to detect. The foreground of this view is geomorphically active, and small rills, young geomorphic surfaces, such as that portrayed in this 1999 view, support young plant assemblages that recover relatively quickly following cessation of disturbance. 40 Guns to Apache Pass, the last film of Audie Murphy, was there in 1966. The 2005 music video Cater 2 U by Destinys Child was filmed at Red Rock Canyon, list of California state parks Campbell Grant, James W. Baird and J. Kenneth Pringle
7.
Amazon basin
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The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about 7,500,000 km2 and it is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname and Venezuela. Most of the basin is covered by the Amazon Rainforest, also known as Amazonia, with a 5,500,000 km2 area of dense tropical forest, this is the largest rainforest in the world. The Amazon River rises in the Andes Mountains at the west of the basin with its tributary the Marañón River in Peru. It is usually considered to be the second longest river in the world, however, a team of Brazilian scientists has claimed that the Amazon is the longest river in the world. It covers about 6,400 km before draining into the Atlantic Ocean, the Amazon and its tributaries form the largest volume of water. The Amazon accounts for about 20% of the water carried to the oceans by rivers. Some of the Amazon rainforests are deforested because of the increasing of cattle ranches, the highest point in the watershed of the Amazon is the peak of Yerupajá at 6,635 m. The Amazon basin formerly flowed west to Pacific Ocean until the Andes formed, politically the basin is divided into the Brazilian Amazônia Legal, the Peruvian Amazon, the Amazon region of Colombia and parts of Bolivia, Ecuador and the Venezuelan state of Amazonas. Plant growth is dense and its variety of inhabitants is comparatively high due to the heavy rainfall. Little sunlight reaches the ground due to the roof canopy by plants. The ground remains dark and damp and only shade tolerant vegetation will grow here, orchids and bromeliads exploit trees and other plants to get closer to the sunlight. They grow hanging onto the branches or tree trunks with aerial roots, not as parasites, species of tropical trees native to the Amazon include Brazil nut, rubber tree and Assai palm. More than 1,400 species of mammals are found in the Amazon and its larger mammals include the jaguar, ocelot, capybara and South American tapir. About 1500 bird species inhabit the Amazon Basin, the biodiversity of the Amazon and the sheer number of diverse bird species is given by the number of different bird families that reside in these humid forests. An example of such would be the family, to which the Guianan cock-of-the-rock belong. Birds such as toucans, and hummingbirds are found here. Macaws are famous for gathering by the hundreds along the cliffs of the Amazon River
8.
Brazil
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Brazil, officially the Federative Republic of Brazil, is the largest country in both South America and Latin America. As the worlds fifth-largest country by area and population, it is the largest country to have Portuguese as an official language. Its Amazon River basin includes a vast tropical forest, home to wildlife, a variety of ecological systems. This unique environmental heritage makes Brazil one of 17 megadiverse countries, Brazil was inhabited by numerous tribal nations prior to the landing in 1500 of explorer Pedro Álvares Cabral, who claimed the area for the Portuguese Empire. Brazil remained a Portuguese colony until 1808, when the capital of the empire was transferred from Lisbon to Rio de Janeiro, in 1815, the colony was elevated to the rank of kingdom upon the formation of the United Kingdom of Portugal, Brazil and the Algarves. Independence was achieved in 1822 with the creation of the Empire of Brazil, a state governed under a constitutional monarchy. The ratification of the first constitution in 1824 led to the formation of a bicameral legislature, the country became a presidential republic in 1889 following a military coup détat. An authoritarian military junta came to power in 1964 and ruled until 1985, Brazils current constitution, formulated in 1988, defines it as a democratic federal republic. The federation is composed of the union of the Federal District, the 26 states, Brazils economy is the worlds ninth-largest by nominal GDP and seventh-largest by GDP as of 2015. A member of the BRICS group, Brazil until 2010 had one of the worlds fastest growing economies, with its economic reforms giving the country new international recognition. Brazils national development bank plays an important role for the economic growth. Brazil is a member of the United Nations, the G20, BRICS, Unasul, Mercosul, Organization of American States, Organization of Ibero-American States, CPLP. Brazil is a power in Latin America and a middle power in international affairs. One of the worlds major breadbaskets, Brazil has been the largest producer of coffee for the last 150 years and it is likely that the word Brazil comes from the Portuguese word for brazilwood, a tree that once grew plentifully along the Brazilian coast. In Portuguese, brazilwood is called pau-brasil, with the word brasil commonly given the etymology red like an ember, formed from Latin brasa and the suffix -il. As brazilwood produces a red dye, it was highly valued by the European cloth industry and was the earliest commercially exploited product from Brazil. The popular appellation eclipsed and eventually supplanted the official Portuguese name, early sailors sometimes also called it the Land of Parrots. In the Guarani language, a language of Paraguay, Brazil is called Pindorama
9.
Subsistence agriculture
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Subsistence agriculture is self-sufficiency farming in which the farmers focus on growing enough food to feed themselves and their families. The output is mostly for local requirements with little or no surplus trade, the typical subsistence farm has a range of crops and animals needed by the family to feed and clothe themselves during the year. Planting decisions are made principally with an eye toward what the family will need during the coming year, tony Waters writes, Subsistence peasants are people who grow what they eat, build their own houses, and live without regularly making purchases in the marketplace. Subsistence agriculture also emerged independently in Mexico where it was based on cultivation. Subsistence agriculture was the dominant mode of production in the world until recently, Subsistence horticulture may have developed independently in South East Asia and Papua New Guinea. Subsistence farming continues today in parts of rural Africa, and parts of Asia. Many of the items, as well as occasional services from physicians, veterinarians, blacksmiths. In Central and Eastern Europe subsistence and semi-subsistence agriculture reappeared within the economy since about 1990. In this type of agriculture, a patch of forest land is cleared by a combination of felling and burning, and crops are grown. After 2-3 years the fertility of the soil begins to decline, the land is abandoned, while the land is left fallow the forest regrows in the cleared area and soil fertility and biomass is restored. After a decade or more, the farmer may return to the first piece of land, shifting cultivation is called Dredd in India, Ladang in Indonesia and Milpa in Central America and Mexico. However, such farmers often recognize the value of such compost and they also may irrigate part of such fields if they are near a source of water. In some areas of tropical Africa, at least, such smaller fields may be ones in which crops are grown on raised beds, thus farmers practicing slash and burn agriculture are often much more sophisticated agriculturalists than the term slash and burn subsistence farmers suggest. In this type of farming people migrate along with their animals from one place to another in search of fodder for their animals, generally they rear cattle, sheep, goats, camels and/or yaks for milk, skin, meat and wool. This way of life is common in parts of central and western Asia, India, east and south-west Africa, examples are the nomadic Bhotiyas and Gujjars of the Himalayas. In Intensive subsistence agriculture, the farmer cultivates a small plot of land using simple tools, climate, with large number of days with sunshine and fertile soils permits growing of more than one crop annually on the same plot. Farmers use their land holdings to produce enough, for their local consumption. It results in more food being produced per acre compared to other subsistence patterns
10.
Latin
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Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Italian and French have contributed many words to the English language, Latin and Ancient Greek roots are used in theology, biology, and medicine. By the late Roman Republic, Old Latin had been standardised into Classical Latin, Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the language from the 3rd century. Later, Early Modern Latin and Modern Latin evolved, Latin was used as the language of international communication, scholarship, and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the language of the Holy See and the Roman Rite of the Catholic Church. Today, many students, scholars and members of the Catholic clergy speak Latin fluently and it is taught in primary, secondary and postsecondary educational institutions around the world. The language has been passed down through various forms, some inscriptions have been published in an internationally agreed, monumental, multivolume series, the Corpus Inscriptionum Latinarum. Authors and publishers vary, but the format is about the same, volumes detailing inscriptions with a critical apparatus stating the provenance, the reading and interpretation of these inscriptions is the subject matter of the field of epigraphy. The works of several hundred ancient authors who wrote in Latin have survived in whole or in part and they are in part the subject matter of the field of classics. The Cat in the Hat, and a book of fairy tales, additional resources include phrasebooks and resources for rendering everyday phrases and concepts into Latin, such as Meissners Latin Phrasebook. The Latin influence in English has been significant at all stages of its insular development. From the 16th to the 18th centuries, English writers cobbled together huge numbers of new words from Latin and Greek words, dubbed inkhorn terms, as if they had spilled from a pot of ink. Many of these words were used once by the author and then forgotten, many of the most common polysyllabic English words are of Latin origin through the medium of Old French. Romance words make respectively 59%, 20% and 14% of English, German and those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch, Roman engineering had the same effect on scientific terminology as a whole
11.
Rock (geology)
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Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a rock, is a combination of the minerals quartz, feldspar. The Earths outer solid layer, the lithosphere, is made of rock, rock has been used by mankind throughout history. The minerals and metals found in rocks have been essential to human civilization, three major groups of rocks are defined, igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is a component of geology. At a granular level, rocks are composed of grains of minerals, the aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed, many rocks contain silica, a compound of silicon and oxygen that forms 74. 3% of the Earths crust. This material forms crystals with other compounds in the rock, the proportion of silica in rocks and minerals is a major factor in determining their name and properties. Rocks are geologically classified according to such as mineral and chemical composition, permeability, the texture of the constituent particles. These physical properties are the end result of the processes that formed the rocks, over the course of time, rocks can transform from one type into another, as described by the geological model called the rock cycle. These events produce three general classes of rock, igneous, sedimentary, and metamorphic, the three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks, hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series. Igneous rock forms through the cooling and solidification of magma or lava and this magma can be derived from partial melts of pre-existing rocks in either a planets mantle or crust. Typically, the melting of rocks is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, igneous rocks are divided into two main categories, plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earths crust, a common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta, the chemical abundance and the rate of cooling of magma typically forms a sequence known as Bowens reaction series. Most major igneous rocks are found along this scale, about 64. 7% of the Earths crust by volume consists of igneous rocks, making it the most plentiful category. Of these, 66% are basalts and gabbros, 16% are granite, only 0. 6% are syenites and 0. 3% peridotites and dunites
12.
Soil
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Soil is a mixture of minerals, organic matter, gases, liquids, and countless organisms that together support life on Earth. Soil is called the Skin of the Earth and interfaces with the lithosphere, the hydrosphere, the atmosphere, the term pedolith, used commonly to refer to the soil, literally translates ground stone. Soil consists of a phase of minerals and organic matter, as well as a porous phase that holds gases. Accordingly, soils are often treated as a system of solids, liquids. Soil is a product of the influence of climate, relief, organisms, Soil continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering with associated erosion. Given its complexity and strong internal connectedness soil has been considered as an ecosystem by soil ecologists. Most soils have a dry bulk density between 1.1 and 1.6 g/cm3, while the particle density is much higher. Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic, Soil science has two basic branches of study, edaphology and pedology. Edaphology is concerned with the influence of soils on living things, pedology is focused on the formation, description, and classification of soils in their natural environment. In engineering terms, soil is referred to as regolith, or loose material that lies above the solid geology. Soil is commonly referred to as earth or dirt, technically, as soil resources serve as a basis for food security, the international community advocates its sustainable and responsible use through different types of soil governance. Soil is a component of the Earths ecosystem. The worlds ecosystems are impacted in far-reaching ways by the carried out in the soil, from ozone depletion and global warming, to rainforest destruction. Following the atmosphere, the soil is the next largest carbon reservoir on Earth, as the planet warms, soils will add carbon dioxide to the atmosphere due to its increased biological activity at higher temperatures. Thus, soil carbon losses likely have a positive feedback response to global warming. Since soil has a range of available niches and habitats. A gram of soil can contain billions of organisms, belonging to thousands of species, mostly microbial, Soil has a mean prokaryotic density of roughly 108 organisms per gram, whereas the ocean has no more than 107 procaryotic organisms per milliliter of seawater. Since plant roots need oxygen, ventilation is an important characteristic of soil and this ventilation can be accomplished via networks of interconnected soil pores, which also absorb and hold rainwater making it readily available for plant uptake
13.
Sediment
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For sediment in beverages, see dregs. For example, sand and silt can be carried in suspension in water and on reaching the sea be deposited by sedimentation. Sediments are most often transported by water, but also wind, beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of transport and deposition. Glacial moraine deposits and till are ice-transported sediments, sediment can be classified based on its grain size and/or its composition. Sediment size is measured on a log base 2 scale, called the Phi scale, composition of sediment can be measured in terms of, parent rock lithology mineral composition chemical make-up. This leads to an ambiguity in which clay can be used as both a size-range and a composition, sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, rivers and streams carry sediment in their flows. This sediment can be in a variety of locations within the flow and these relationships are shown in the following table for the Rouse number, which is a ratio of sediment fall velocity to upwards velocity. If the upwards velocity is less than the settling velocity, but still high enough for the sediment to move, it will move along the bed as bed load by rolling, sliding. If the upwards velocity is higher than the velocity, the sediment will be transported high in the flow as wash load. As there are generally a range of different particle sizes in the flow, sediment motion can create self-organized structures such as ripples, dunes, antidunes on the river or stream bed. These bedforms are often preserved in rocks and can be used to estimate the direction. Overland flow can erode soil particles and transport them downslope, the erosion associated with overland flow may occur through different methods depending on meteorological and flow conditions. If the initial impact of rain droplets dislodges soil, the phenomenon is called rainsplash erosion, if overland flow is directly responsible for sediment entrainment but does not form gullies, it is called sheet erosion. If the flow and the substrate permit channelization, gullies may form, glaciers carry a wide range of sediment sizes, and deposit it in moraines. The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation and this expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow. This can be localized, and simply due to obstacles, examples are scour holes behind boulders, where flow accelerates
14.
Erosion
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In earth science, erosion is the action of surface processes that remove soil, rock, or dissolved material from one location on the Earths crust, then transport it away to another location. Eroded sediment or solutes may be transported just a few millimetres, the rates at which such processes act control how fast a surface is eroded. Feedbacks are also possible between rates of erosion and the amount of eroded material that is carried by, for example. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, while erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the rate of erosion in the region. Excessive erosion causes both on-site and off-site problems, on-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of bodies, as well as sediment-related damage to roads. Intensive agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion, however, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, and the surface runoff which may result from rainfall, produces four types of soil erosion, splash erosion, sheet erosion, rill erosion. Splash erosion is generally seen as the first and least severe stage in the erosion process. In splash erosion, the impact of a falling raindrop creates a crater in the soil. The distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rate is greater than the rate at which water can infiltrate into the soil. If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope, sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes, generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimetres or less and this means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow
15.
Ocean
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An ocean is a body of saline water that composes much of a planets hydrosphere. On Earth, an ocean is one of the major divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, the word sea is often used interchangeably with ocean in American English but, strictly speaking, a sea is a body of saline water partly or fully enclosed by land. The ocean contains 97% of Earths water, and oceanographers have stated that less than 5% of the World Ocean has been explored, the total volume is approximately 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters. As the world ocean is the component of Earths hydrosphere, it is integral to all known life, forms part of the carbon cycle. The world ocean is the habitat of 230,000 known species, but because much of it is unexplored, the origin of Earths oceans remains unknown, oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds, the only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many planets and natural satellites, notably. The Solar Systems giant planets are thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of water within a circumstellar habitable zone. Ocean planets are a type of planet with a surface completely covered with liquid. The concept of Ōkeanós has an Indo-European connection, Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases, though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a body of water with relatively free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions – listed below in descending order of area and volume – are defined in part by the continents, various archipelagos, Oceans are fringed by smaller, adjoining bodies of water such as seas, gulfs, bays, bights, and straits. The Mid-Oceanic Ridge of the World are connected and form the Ocean Ridge, the continuous mountain range is 65,000 km long, and the total length of the oceanic ridge system is 80,000 km long
16.
Silt
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Silt is granular material of a size between sand and clay, whose mineral origin is quartz and feldspar. Silt may occur as a soil or as sediment mixed in suspension with water in a body of such as a river. It may also exist as soil deposited at the bottom of a water body, Silt has a moderate specific area with a typically non-sticky, plastic feel. Silt usually has a floury feel when dry, and a slippery feel when wet, Silt can be visually observed with a hand lens. Silt is created by a variety of physical processes capable of splitting the generally sand-sized quartz crystals of primary rocks by exploiting deficiencies in their lattice and these involve chemical weathering of rock and regolith, and a number of physical weathering processes such as frost shattering and haloclasty. The main process is abrasion through transport, including fluvial comminution, aeolian attrition and it is in semi-arid environments that substantial quantities of silt are produced. Silt is sometimes known as rock flour or stone dust, especially produced by glacial action. Mineralogically, silt is composed mainly of quartz and feldspar, sedimentary rock composed mainly of silt is known as siltstone. Liquefaction created by an earthquake is silt suspended in water that is hydrodynamically forced up from below ground level. In the Udden–Wentworth scale, silt particles range between 0.0039 and 0.0625 mm, larger than clay but smaller than sand particles, ISO14688 grades silts between 0.002 mm and 0.063 mm. In actuality, silt is chemically distinct from clay, and unlike clay, grains of silt are approximately the size in all dimensions, furthermore. Clays are formed from thin plate-shaped particles held together by electrostatic forces, according to the U. S. Department of Agriculture Soil Texture Classification system, the sand-silt distinction is made at the 0.05 mm particle size. The USDA system has been adopted by the Food and Agriculture Organization, in the Unified Soil Classification System and the AASHTO Soil Classification system, the sand-silt distinction is made at the 0.075 mm particle size. Silts and clays are distinguished mechanically by their plasticity, Silt is easily transported in water or other liquid and is fine enough to be carried long distances by air in the form of dust. Thick deposits of silty material resulting from deposition by aeolian processes are called loess. Silt and clay contribute to turbidity in water, Silt is transported by streams or by water currents in the ocean. When silt appears as a pollutant in water the phenomenon is known as siltation, Silt, deposited by annual floods along the Nile River, created the rich, fertile soil that sustained the Ancient Egyptian civilization. In south east Bangladesh, in the Noakhali district, cross dams were built in the 1960s whereby silt gradually started forming new land called chars, the district of Noakhali has gained more than 28 square miles of land in the past 50 years
17.
Clay
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Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to water content and become hard, brittle. Depending on the content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size, silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in size and other physical properties. The distinction between silt and clay varies by discipline, geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm, sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils Atterberg limits, ISO14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. These solvents, usually acidic, migrate through the rock after leaching through upper weathered layers. In addition to the process, some clay minerals are formed through hydrothermal activity. There are two types of deposits, primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation, secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are associated with very low energy depositional environments such as large lakes. Depending on the source, there are three or four main groups of clays, kaolinite, montmorillonite-smectite, illite, and chlorite. Chlorites are not always considered to be a clay, sometimes being classified as a group within the phyllosilicates. There are approximately 30 different types of clays in these categories. Varve is clay with visible annual layers, which are formed by deposition of those layers and are marked by differences in erosion. This type of deposit is common in glacial lakes
18.
Sand
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Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt, Sand can also refer to a textural class of soil or soil type, i. e. a soil containing more than 85% sand-sized particles by mass. The second most common type of sand is calcium carbonate, for example aragonite, for example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean. Sand is a non renewable resource over human timescales, and sand suitable for making concrete is in high demand, in terms of particle size as used by geologists, sand particles range in diameter from 0.0625 mm to 2 mm. An individual particle in this size is termed a sand grain. Sand grains are between gravel and silt, a 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A1938 specification of the United States Department of Agriculture was 0.05 mm. Sand feels gritty when rubbed between the fingers. ISO14688 grades sands as fine, medium and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the United States, sand is commonly divided into five sub-categories based on size, very fine sand, fine sand, medium sand, coarse sand, and very coarse sand. These sizes are based on the Krumbein phi scale, where size in Φ = -log2D, on this scale, for sand the value of Φ varies from −1 to +4, with the divisions between sub-categories at whole numbers. The composition of sand is highly variable, depending on the local rock sources. The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a granitic rock outcrop. Some sands contain magnetite, chlorite, glauconite or gypsum, Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian. Chlorite-glauconite bearing sands are typically green in color, as are sands derived from basaltic with a high olivine content, many sands, especially those found extensively in Southern Europe, have iron impurities within the quartz crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain garnets and other resistant minerals, the study of individual grains can reveal much historical information as to the origin and kind of transport of the grain. Quartz sand that is weathered from granite or gneiss quartz crystals will be angular. It is called grus in geology or sharp sand in the trade where it is preferred for concrete. Sand that is transported long distances by water or wind will be rounded, people who collect sand as a hobby are known as arenophiles
19.
Gravel
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Gravel /ˈɡrævəl/ is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel is categorized by the Udden-Wentworth scale into granular gravel and pebble gravel, one cubic metre of gravel typically weighs about 1,800 kg. Gravel is an important commercial product, with a number of applications, many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or tarmac, both sand and small gravel are also important for the manufacture of concrete. Large gravel deposits are a geological feature, being formed as a result of the weathering. The action of rivers and waves tends to pile up gravel in large accumulations and this can sometimes result in gravel becoming compacted and concreted into the sedimentary rock called conglomerate. Where natural gravel deposits are insufficient for human purposes, gravel is often produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, quarries where gravel is extracted are known as gravel pits. Southern England possesses particularly large concentrations of them due to the deposition of gravel in the region during the Ice Ages. As of 2006, the United States is the leading producer and consumer of gravel. The word gravel comes from the Breton language, adding the -el suffix in Breton denotes the component parts of something larger. Thus gravel means the stones which make up such a beach on the coast. Many dictionaries ignore the Breton language, citing Old French gravele or gravelle, Gravel often has the meaning a mixture of different size pieces of stone mixed with sand and possibly some clay. American English also allows small stones without sand mixed in also known as crushed stone, types of gravel include, Bank gravel, naturally deposited gravel intermixed with sand or clay found in and next to rivers and streams. Also known as Bank run or River run, bench gravel, a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level. Creek rock, this is rounded, semi-polished stones, potentially of a wide range of types. It is also used as concrete aggregate and less often as a paving surface. Crushed stone, rock crushed and graded by screens and then mixed to a blend of stones and fines and it is widely used as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may be made from granite, limestone, dolomite, also known as crusher run, DGA QP, and shoulder stone
20.
Lithology
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It may be either a detailed description of these characteristics or be a summary of the gross physical character of a rock. It is the basis of subdividing rock sequences into individual lithostratigraphic units for the purposes of mapping, in certain applications, such as site investigations, lithology is described using a standard terminology such as in the European geotechnical standard Eurocode 7. The naming of a lithology is based on the rock type, the three major rock types are sedimentary, igneous, metamorphic. Sedimentary rocks are classified by whether they are siliciclastic or carbonate. Siliciclastic sedimentary rocks are then subcategorized based on their size distribution and the relative proportions of quartz, feldspar. Carbonate rocks are classified with the Dunham or Folk classification schemes according to the constituents of the carbonate rock, the name of an igneous rock requires information on crystal size and mineralogy. This classification can often be performed with a QAPF diagram, metamorphic rock naming can be based on texture, protolith, metamorphic facies, and/or the locations in which they are found. Naming based on texture and a pelite protolith can be used to slate and phyllite. Texture-based names are schist and gneiss and these textures, from slate to gneiss, define a continually-increasing extent of metamorphism. Metamorphic facies are defined by the fields in which particular minerals form. In igneous and metamorphic rocks, grain size is a measure of the sizes of the crystals in the rock. In igneous rock, this is used to determine the rate at which the material cooled, large crystals typically indicate intrusive igneous rock, as metamorphic reactions progress, the grains in metamorphic rocks can often be broken down into smaller grains. In clastic sedimentary rocks, grain size is the diameter of the grains and/or clasts that constitute the rock and these are used to determine which rock naming system to use. In the case of sandstones and conglomerates, which cover a range of grain sizes. Examples are pebble conglomerate and fine quartz arenite, in rocks in which mineral grains are large enough to be identified using a hand lens, the visible mineralogy is included as part of the description. The mineralogical composition of a rock is one of the ways in which it is classified. In general, igneous rocks can be categorized by increasing silica content as ultramafic, mafic, intermediate, or felsic, the fabric of a rock describes the spatial and geometric configuration of all the elements that make it up. In sedimentary rocks the main fabric is normally bedding and the scale
21.
Lake
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A lake is an area of variable size filled with water, localized in a basin, that is surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, and therefore are distinct from lagoons, Lakes can be contrasted with rivers or streams, which are usually flowing. Most lakes are fed and drained by rivers and streams, natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Other lakes are found in endorheic basins or along the courses of mature rivers, in some parts of the world there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will fill in with sediments or spill out of the basin containing them. The word lake comes from Middle English lake, from Old English lacu, from Proto-Germanic *lakō, cognates include Dutch laak, Middle Low German lāke as in, de, Moorlake, de, Wolfslake, de, Butterlake, German Lache, and Icelandic lækur. Also related are the English words leak and leach, none of these definitions completely excludes ponds and all are difficult to measure. For this reason, simple size-based definitions are used to separate ponds. One definition of lake is a body of water of 2 hectares or more in area, however, others have defined lakes as waterbodies of 5 hectares and above, or 8 hectares and above. Charles Elton, one of the founders of ecology, regarded lakes as waterbodies of 40 hectares or more. The term lake is used to describe a feature such as Lake Eyre. In common usage, many bear names ending with the word pond. One textbook illustrates this point with the following, In Newfoundland, for example, almost every lake is called a pond, whereas in Wisconsin, the majority of lakes on Earth are fresh water, and most lie in the Northern Hemisphere at higher latitudes. Canada, with a drainage system has an estimated 31,752 lakes larger than 3 square kilometres and an unknown total number of lakes. Finland has 187,888 lakes 500 square metres or larger, most lakes have at least one natural outflow in the form of a river or stream, which maintain a lakes average level by allowing the drainage of excess water. Some lakes do not have an outflow and lose water solely by evaporation or underground seepage or both. Many lakes are artificial and are constructed for power generation, aesthetic purposes, recreational purposes, industrial use. Globally, lakes are greatly outnumbered by ponds, of an estimated 304 million standing water bodies worldwide, 91% are 1 hectare or less in area
22.
Fluvial
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Fluvial is a term used in geography and geology to refer to the processes associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, fluvial processes include the motion of sediment and erosion or deposition on the river bed. Erosion by moving water can happen in two ways, firstly, the movement of water across the bed exerts a shear stress directly onto the bed. However, if the river carries significant quantities of sediment, this material can act as tools to enhance wear of the bed, at the same time the fragments themselves are ground down, becoming smaller and more rounded. Sediment in rivers is transported as either bedload or suspended load, there is also a component carried as dissolved material. For each grain size there is a velocity at which the grains start to move. However the grains will continue to be transported even if the velocity falls below the entrainment velocity due to the friction between the grains and the river bed. Eventually the velocity will fall low enough for the grains to be deposited and this is shown by the Hjulstrøm curve. A river is continually picking up and dropping solid particles of rock, where the river flow is fast, more particles are picked up than dropped. Where the river flow is slow, more particles are dropped than picked up, areas where more particles are dropped are called alluvial or flood plains, and the dropped particles are called alluvium. Even small streams make alluvial deposits, but it is in the plains and deltas of large rivers that large. The amount of matter carried by a river is enormous. The names of rivers derive from the color that the transported matter gives the water. For example, the Huang He in China is literally translated Yellow River, and it has been estimated that the Mississippi River annually carries 406 million tons of sediment to the sea, the Yellow River 796 million tons, and the Po River in Italy 67 million tons. Lacustrine - of or relating to a lake maritime - of or relating the sea oceanic - of or relating to an ocean palustrine - of or relating to a marsh
23.
Glacial till
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Till or glacial till is unsorted glacial sediment. Till is derived from the erosion and entrainment of material by the ice of a glacier. It is deposited some distance down-ice to form terminal, lateral, medial, till is classified into primary deposits, laid down directly by glaciers, and secondary deposits, reworked by fluvial transport and other processes. Glacial drift is the graded and extremely heterogeneous sediment of a glacier. Its content may vary from clays to mixtures of clay, sand, gravel and this material is mostly derived from the subglacial erosion and entrainment by the moving ice of the glaciers of previously available unconsolidated sediments. Bedrock can also be eroded through the action of glacial plucking and abrasion, eventually, the sedimentary assemblage forming this bed will be abandoned some distance down-ice from its various sources. This is the process of glacial till deposition, when this deposition occurs at the base of the moving ice of a glacier, the sediment is called lodgement till. Rarely, eroded unconsolidated sediments can be preserved in the till along with their original sedimentary structures, till is deposited at the terminal moraine, along the lateral and medial moraines and in the ground moraine of a glacier. Prospectors use trace minerals in tills as clues to follow the glacier upstream to find kimberlite diamond deposits, in cases where till has been indurated or lithified by subsequent burial into solid rock, it is known as the sedimentary rock tillite. Matching beds of ancient tillites on opposite sides of the south Atlantic Ocean provided early evidence for continental drift, the same tillites also provide some support to the Precambrian Snowball Earth glaciation event hypothesis. There are various types of classifying tills, primary deposits – laid down directly by glacier action secondary deposits – reworked by fluvial transport, erosion, traditionally a further set of divisions has been made to primary deposits, based upon the method of deposition. Lodgement tills – sediment which has been deposited by plastering of glacial debris from a sliding glacier bed, deformation tills – Sediment which has been disaggregated and homogenised by shearing in the sub glacial deformed layer. Melt out tills – Released by melting of stagnant or slowly moving debris-rich glacier ice, split up into sub glacial melt out till and supraglacial melt-out till. Sublimation till – similar to melt out till, except the ice is lost through sublimation rather than melt, often occurs only in extremely cold and arid conditions, mainly in Antarctica. Van der Meer et al.2003 have suggested that these classifications are outdated and should instead be replaced with only one classification
24.
River
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A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water, small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the term river as applied to geographic features. Many names for small rivers are specific to geographic location, examples are run in parts of the United States, burn in Scotland and northeast England. Sometimes a river is defined as being larger than a creek, but not always, Rivers are part of the hydrological cycle. Potamology is the study of rivers while limnology is the study of inland waters in general. Extraterrestrial rivers of liquid hydrocarbons have recently found on Titan. Channels may indicate past rivers on other planets, specifically outflow channels on Mars and rivers are theorised to exist on planets, a river begins at a source, follows a path called a course, and ends at a mouth or mouths. The water in a river is confined to a channel. In larger rivers there is also a wider floodplain shaped by flood-waters over-topping the channel. Floodplains may be wide in relation to the size of the river channel. This distinction between river channel and floodplain can be blurred, especially in areas where the floodplain of a river channel can become greatly developed by housing. Rivers can flow down mountains, through valleys or along plains, the term upriver refers to the direction towards the source of the river, i. e. against the direction of flow. Likewise, the term describes the direction towards the mouth of the river. The term left bank refers to the bank in the direction of flow. The river channel typically contains a stream of water, but some rivers flow as several interconnecting streams of water. Extensive braided rivers are now found in only a few regions worldwide and they also occur on peneplains and some of the larger river deltas. Anastamosing rivers are similar to braided rivers and are quite rare
25.
Quaternary
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Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy. It follows the Neogene Period and spans from 2.588 ±0.005 million years ago to the present, the Quaternary Period is divided into two epochs, the Pleistocene and the Holocene. The informal term Late Quaternary refers to the past 0. 5–1.0 million years, the Quaternary Period is typically defined by the cyclic growth and decay of continental ice sheets driven by Milankovitch cycles and the associated climate and environmental changes that occurred. The term Quaternary was proposed by Giovanni Arduino in 1759 for alluvial deposits in the Po River valley in northern Italy and it was introduced by Jules Desnoyers in 1829 for sediments of Frances Seine Basin that seemed clearly to be younger than Tertiary Period rocks. The Quaternary Period follows the Neogene Period and extends to the present, the Quaternary covers the time span of glaciations classified as the Pleistocene, and includes the present interglacial time-period, the Holocene. This places the start of the Quaternary at the onset of Northern Hemisphere glaciation approximately 2.6 million years ago, Quaternary stratigraphers usually worked with regional subdivisions. From the 1970s, the International Commission on Stratigraphy tried to make a single geologic time scale based on GSSPs, the Quaternary subdivisions were defined based on biostratigraphy instead of paleoclimate. This led to the problem that the base of the Pleistocene was at 1.805 Mya. The ICS then proposed to use of the name Quaternary altogether. The Anthropocene has been proposed as an epoch as a mark of the anthropogenic impact on the global environment starting with the Industrial Revolution. The Anthropocene is not officially designated by the ICS, however, the 2.6 million years of the Quaternary represents the time during which recognizable humans existed. Over this short period, there has been relatively little change in the distribution of the continents due to plate tectonics. The Quaternary geological record is preserved in detail than that for earlier periods. The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude, there was a major extinction of large mammals in Northern areas at the end of the Pleistocene Epoch. Many forms such as saber-toothed cats, mammoths, mastodons, glyptodonts, others, including horses, camels and American cheetahs became extinct in North America. Glaciation took place repeatedly during the Quaternary Ice Age – a term coined by Schimper in 1839 that began with the start of the Quaternary about 2.58 Mya and continues to the present-day. In 1821, a Swiss engineer, Ignaz Venetz, presented an article in which he suggested the presence of traces of the passage of a glacier at a distance from the Alps. This idea was initially disputed by another Swiss scientist, Louis Agassiz, a year later, Agassiz raised the hypothesis of a great glacial period that would have had long-reaching general effects
26.
Sedimentary basin
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Sedimentary basins are regions of Earth of long-term subsidence creating accommodation space for infilling by sediments. Sedimentary basins occur in diverse geological settings usually associated with tectonic activity. Basins formed in different plate tectonic regimes vary in their preservation potential, on oceanic crust, basins are likely to be subducted, while marginal continental basins may be partially preserved, and intracratonic basins have a high probability of preservation. As the sediments are buried, they are subjected to increasing pressure, a number of basins formed in extensional settings can undergo inversion which has accounted for a number of the economically viable oil reserves on earth which were formerly basins. Sedimentary basins form primarily in convergent, divergent and transform settings, convergent boundaries create foreland basins through tectonic compression of oceanic and continental crust during lithospheric flexure. Tectonic extension at divergent boundaries where continental rifting is occurring can create a nascent ocean basin leading to either an ocean or the failure of the rift zone. If the lithosphere is caused to stretch horizontally, by such as ridge-push or trench-pull. The lower, hotter part of the lithosphere will flow away from the main area being stretched, whilst the upper, cooler and more brittle crust will tend to fault. The combined effect of two mechanisms is for the Earths surface in the area of extension to subside, creating a geographical depression which is then often infilled with water and/or sediments. An example of a basin caused by lithospheric stretching is the North Sea – also an important location for significant hydrocarbon reserves, another such feature is the Basin and Range Province which covers most of the USA state of Nevada, forming a series of horst and graben structures. Another expression of lithospheric stretching results in the formation of basins with central ridges, The Red Sea is in fact an incipient ocean. The mouth of the Red Sea is also a triple junction where the Indian Ocean Ridge, Red Sea Rift. This is the place on the planet where such a triple junction in oceanic crust is exposed subaerially. The reason for this is twofold, due to a high thermal buoyancy of the junction, if a load is placed on the lithosphere, it will tend to flex in the manner of an elastic plate. The magnitude of the lithospheric flexure is a function of the load and the flexural rigidity of the lithosphere. Flexural rigidity is in itself, a function of the mineral composition, thermal regime. The nature of the load is varied, for instance, the Hawaiian Islands chain of volcanic edifices has sufficient mass to cause deflection in the lithosphere. Deformation of the lithosphere in the plane of the earth occurs as a result of near horizontal maximum and minimum principal stresses, the resulting zones of subsidence are known as strike-slip or pull-apart basins
27.
Pliocene
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The Pliocene Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era, the Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch.588 to 1.806 million years ago, and is now included in the Pleistocene. As with other geologic periods, the geological strata that define the start and end are well identified but the exact dates of the start. The boundaries defining the Pliocene are not set at an easily identified worldwide event, the upper boundary was set at the start of the Pleistocene glaciations. The Pliocene was named by Sir Charles Lyell, the name comes from the Greek words πλεῖον and καινός and means roughly continuation of the recent, referring to the essentially modern marine mollusc faunas. H. W. Fowler called the term a regrettable barbarism, in the official timescale of the ICS, the Pliocene is subdivided into two stages. From youngest to oldest they are, Piacenzian Zanclean The Piacenzian is sometimes referred to as the Late Pliocene, in the system of North American Land Mammal Ages include Hemphillian, and Blancan. The Blancan extends forward into the Pleistocene, South American Land Mammal Ages include Montehermosan, Chapadmalalan and Uquian. In the Paratethys area the Pliocene contains the Dacian and Romanian stages, as usual in stratigraphy, there are many other regional and local subdivisions in use. In Britain the Pliocene is divided into the stages, Gedgravian, Waltonian, Pre-Ludhamian, Ludhamian, Thurnian, Bramertonian or Antian, Pre-Pastonian or Baventian, Pastonian and Beestonian. The exact correlations between these stages and the ICS stages is still a matter of detail. The formation of an Arctic ice cap is signaled by a shift in oxygen isotope ratios and ice-rafted cobbles in the North Atlantic. Mid-latitude glaciation was probably underway before the end of the epoch, the global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas. Continents continued to drift, moving from positions possibly as far as 250 km from their present locations to positions only 70 km from their current locations, africas collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean. The border between the Miocene and the Pliocene is also the time of the Messinian salinity crisis, Sea level changes exposed the land-bridge between Alaska and Asia. Pliocene marine rocks are exposed in the Mediterranean, India. Elsewhere, they are exposed largely near shores, the change to a cooler, dry, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species worldwide. Deciduous forests proliferated, coniferous forests and tundra covered much of the north, tropical forests were limited to a tight band around the equator, and in addition to dry savannahs, deserts appeared in Asia and Africa
28.
Miocene
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The Miocene is the first geological epoch of the Neogene Period and extends from about 23.03 to 5.333 million years ago. The Miocene was named by Sir Charles Lyell and its name comes from the Greek words μείων and καινός and means less recent because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene Epoch and is followed by the Pliocene Epoch, the earth went from the Oligocene through the Miocene and into the Pliocene, with the climate slowly cooling towards a series of ice ages. The Miocene boundaries are not marked by a single distinct global event, the apes arose and diversified during the Miocene, becoming widespread in the Old World. By the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path, as in the Oligocene before it, grasslands continued to expand and forests to dwindle in extent. In the Miocene seas, kelp forests made their first appearance, the plants and animals of the Miocene were fairly modern. The Miocene faunal stages from youngest to oldest are typically named according to the International Commission on Stratigraphy, Two subdivisions each form the lower, middle, continents continued to drift toward their present positions. Mountain building took place in western North America, Europe, both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in the North American Great Plains, India continued to collide with Asia, creating dramatic new mountain ranges. The Tethys Seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish–Arabian region between 19 and 12 Ma. The subsequent uplift of mountains in the western Mediterranean region and a fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea near the end of the Miocene. The global trend was towards increasing aridity caused primarily by global cooling reducing the ability of the atmosphere to absorb moisture, climates remained moderately warm, although the slow global cooling that eventually led to the Pleistocene glaciations continued. Although a long-term cooling trend was well underway, there is evidence of a period during the Miocene when the global climate rivalled that of the Oligocene. The Miocene warming began 21 million years ago and continued until 14 million years ago, by 8 million years ago, temperatures dropped sharply once again, and the Antarctic ice sheet was already approaching its present-day size and thickness. Greenland may have begun to have large glaciers as early as 7 to 8 million years ago, life during the Miocene Epoch was mostly supported by the two newly formed biomes, kelp forests and grasslands. This allows for more grazers, such as horses, rhinoceroses, ninety five percent of modern plants existed by the end of this epoch. The higher organic content and water retention of the deeper and richer grassland soils, with long term burial of carbon in sediments, produced a carbon and this, combined with higher surface albedo and lower evapotranspiration of grassland, contributed to a cooler, drier climate. The expansion of grasslands and radiations among terrestrial herbivores correlates to fluctuations in CO2
29.
San Joaquin River
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The San Joaquin River /ˈsæn wɑːˈkiːn/ is the longest river of Central California in the United States. An important source of water as well as a wildlife corridor. People have inhabited the San Joaquin Valley for more than 8,000 years, the newcomers quickly appropriated the rich natural and hydrologic resources of the watershed for use in farms and cities, but found themselves plagued by flood and drought. Because of the topography of the San Joaquin Valley, floods once transformed much of the lower river into a huge inland sea. In the 20th century, many levees and dams were built on the San Joaquin and these engineering works changed the fluctuating nature of the river forever, and cut off the Tulare Basin from the rest of the San Joaquin watershed. The river was called many different names, at different parts of the river were known by different names. The present name of the dates to 1805–1808, when Spanish explorer Gabriel Moraga was surveying east from Mission San José in order to find possible sites for a mission. Moraga named a tributary of the river for Saint Joachim, husband of Saint Anne and father of Mary, the name Moraga chose was later applied to the entire river, it was in common use by 1810. In the Mono language, the river is called typici h huu, a member of the Pedro Fages party in 1772, Crespis vantage point was the hilltops behind modern San Francisco. Another early name was Rio San Juan Bautista, the origin of which is unknown.8 mi southeast of Mount Lyell, the Middle Fork is usually considered part of the main stem. The South Fork, which begins at Martha Lake in Kings Canyon National Park and flows through Florence Lake, from the mountainous alpine headwaters, the San Joaquin flows generally south into the foothills of the Sierra, passing through four hydroelectric dams. It eventually emerges from the foothills at what was once the town of Millerton, the location of Friant Dam since 1942, which forms Millerton Lake. Below Friant Dam, the San Joaquin flows west-southwest out into the San Joaquin Valley – the southern part of the Great Central Valley – passing north of Fresno, from Mendota, the San Joaquin swings northwest, passing through many different channels, some natural and some man-made. Northeast of Dos Palos, it is joined by the Fresno. Fifty miles downstream, the Merced River empties into an otherwise dry San Joaquin, the majority of the river flows through quiet agricultural bottomlands, and as a result its meandering course manages to avoid most of the urban areas and cities in the San Joaquin Valley. About 11 mi west of Modesto, the San Joaquin meets its largest tributary, near Vernalis, it is joined by another major tributary, the Stanislaus River. About 40 mi from the mouth, the river draws abreast to the flank of Stockton. From here to the mouth, the river is dredged as part of a navigation project, past the head of tide, amid the many islands of the delta, the San Joaquin is joined by two more tributaries, the Calaveras River and the larger Mokelumne
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Ore
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An ore is a type of rock that contains sufficient minerals with important elements including metals that can be economically extracted from the rock. The ores are extracted from the earth through mining, they are refined to extract the valuable element. The grade or concentration of an ore mineral, or metal, as well as its form of occurrence, will directly affect the costs associated with mining the ore. The cost of extraction must thus be weighed against the value contained in the rock to determine what ore can be processed. Metal ores are generally oxides, sulfides, silicates, or native metals that are not commonly concentrated in the Earths crust, the ores must be processed to extract the metals of interest from the waste rock and from the ore minerals. Ore bodies are formed by a variety of geological processes, the process of ore formation is called ore genesis. An ore deposit is an accumulation of ore and this is distinct from a mineral resource as defined by the mineral resource classification criteria. An ore deposit is one occurrence of a particular ore type, Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis. Stratiform arkose-hosted and shale-hosted copper, typified by the Zambian copperbelt and this identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work. This is because the distribution of ores is unequal and dislocated from locations of peak demand. Other, lesser, commodities do not have international clearing houses and benchmark prices and this generally makes determining the price of ores of this nature opaque and difficult. Such metals include lithium, niobium-tantalum, bismuth, antimony and rare earths, most of these commodities are also dominated by one or two major suppliers with >60% of the worlds reserves. The London Metal Exchange aims to add uranium to its list of metals on warrant, the World Bank reports that China was the top importer of ores and metals in 2005 followed by the USA and Japan. Economic geology Mineral resource classification Ore genesis Petrology Froth Flotation Extractive metallurgy DILL, the “chessboard” classification scheme of mineral deposits, Mineralogy and geology from aluminum to zirconium, Earth-Science Reviews, Volume 100, Issue 1-4, June 2010, Pages 1-420
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Gold
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Gold is a chemical element with symbol Au and atomic number 79. In its purest form, it is a bright, slightly yellow, dense, soft, malleable. Chemically, gold is a metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions, Gold often occurs in free elemental form, as nuggets or grains, in rocks, in veins, and in alluvial deposits. It occurs in a solid solution series with the element silver and also naturally alloyed with copper. Less commonly, it occurs in minerals as gold compounds, often with tellurium, golds atomic number of 79 makes it one of the higher numbered, naturally occurring elements. It is thought to have produced in supernova nucleosynthesis, from the collision of neutron stars. Because the Earth was molten when it was formed, almost all of the present in the early Earth probably sank into the planetary core. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of acid and hydrochloric acid. Gold also dissolves in solutions of cyanide, which are used in mining and electroplating. Gold dissolves in mercury, forming amalgam alloys, but this is not a chemical reaction, as a precious metal, gold has been used for coinage, jewelry, and other arts throughout recorded history. A total of 186,700 tonnes of gold is in existence above ground, the world consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry. Gold is also used in infrared shielding, colored-glass production, gold leafing, certain gold salts are still used as anti-inflammatories in medicine. As of 2014, the worlds largest gold producer by far was China with 450 tonnes, Gold is cognate with similar words in many Germanic languages, deriving via Proto-Germanic *gulþą from Proto-Indo-European *ǵʰelh₃-. The symbol Au is from the Latin, aurum, the Latin word for gold, the Proto-Indo-European ancestor of aurum was *h₂é-h₂us-o-, meaning glow. This word is derived from the root as *h₂éu̯sōs, the ancestor of the Latin word Aurora. This etymological relationship is presumably behind the frequent claim in scientific publications that aurum meant shining dawn, Gold is the most malleable of all metals, a single gram can be beaten into a sheet of 1 square meter, and an avoirdupois ounce into 300 square feet. Gold leaf can be thin enough to become semi-transparent
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Platinum
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Platinum is a chemical element with symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious and its name is derived from the Spanish term platina, translated into little silver. Platinum is a member of the group of elements and group 10 of the periodic table of elements. It has six naturally occurring isotopes and it is one of the rarer elements in Earths crust with an average abundance of approximately 5 μg/kg. It occurs in some nickel and copper ores along with some deposits, mostly in South Africa. Because of its scarcity in Earths crust, only a few hundred tonnes are produced annually, Platinum is one of the least reactive metals. It has remarkable resistance to corrosion, even at high temperatures, consequently, platinum is often found chemically uncombined as native platinum. Because it occurs naturally in the sands of various rivers. Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewelry. Being a heavy metal, it leads to health issues upon exposure to its salts, compounds containing platinum, such as cisplatin, oxaliplatin and carboplatin, are applied in chemotherapy against certain types of cancer. Pure platinum is a lustrous, ductile, and malleable, silver-white metal, Platinum is more ductile than gold, silver or copper, thus being the most ductile of pure metals, but it is less malleable than gold. The metal has excellent resistance to corrosion, is stable at temperatures and has stable electrical properties. Platinum reacts with oxygen slowly at high temperatures. It reacts vigorously with fluorine at 500 °C to form platinum tetrafluoride and it is also attacked by chlorine, bromine, iodine, and sulfur. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in hot aqua regia to form chloroplatinic acid and its physical characteristics and chemical stability make it useful for industrial applications. Its resistance to wear and tarnish is well suited to use in fine jewelry, the most common oxidation states of platinum are +2 and +4. The +1 and +3 oxidation states are common, and are often stabilized by metal bonding in bimetallic species. As is expected, tetracoordinate platinum compounds tend to adopt 16-electron square planar geometries, Platinum has six naturally occurring isotopes, 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt
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Gemstone
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A gemstone is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks or organic materials that are not minerals are used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone, apart from jewelry, from earliest antiquity engraved gems and hardstone carvings, such as cups, were major luxury art forms. A gem maker is called a lapidary or gemcutter, a worker is a diamantaire. The carvings of Carl Fabergé are significant works in this tradition, the traditional classification in the West, which goes back to the ancient Greeks, begins with a distinction between precious and semi-precious, similar distinctions are made in other cultures. In modern usage the precious stones are diamond, ruby, sapphire, other stones are classified by their color, translucency and hardness. Another unscientific term for semi-precious gemstones used in art history and archaeology is hardstone, in modern times gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition, for example, diamonds are made of carbon and rubies of aluminium oxide. Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic, another term used is habit, the form the gem is usually found in. For example, diamonds, which have a crystal system, are often found as octahedrons. Gemstones are classified into different groups, species, and varieties, for example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Other examples are the Emerald, aquamarine, red beryl, goshenite, heliodor, and morganite, gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and luster. They may exhibit pleochroism or double refraction and they may have luminescence and a distinctive absorption spectrum. Material or flaws within a stone may be present as inclusions, gemstones may also be classified in terms of their water. This is a grading of the gems luster, transparency. Very transparent gems are considered first water, while second or third water gems are those of a lesser transparency, there is no universally accepted grading system for gemstones. Diamonds are graded using a system developed by the Gemological Institute of America in the early 1950s, historically, all gemstones were graded using the naked eye
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Placer deposit
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In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation during sedimentary processes. The name is from the Spanish word placer, meaning alluvial sand, Placer mining is an important source of gold, and was the main technique used in the early years of many gold rushes, including the California Gold Rush. Types of placer deposits include alluvium, eluvium, beach placers, Placer materials must be both dense and resistant to weathering processes. To accumulate in placers, mineral particles must be significantly denser than quartz, Placer environments typically contain black sand, a conspicuous shiny black mixture of iron oxides, mostly magnetite with variable amounts of ilmenite and hematite. Valuable mineral components often occurring with black sands are monazite, rutile, zircon, chromite, wolframite, alluvial placers are formed by the deposition of dense particles at a site where water velocity remains below that required to transport them further. To form a deposit, the particles desired must show a marked density contrast with the gangue material. Only if the deposit is winnowed in this way can the minerals be concentrated to economic levels, beach placers are formed in sand and gravel deposited along the edge of large bodies of water. Heavy mineral sands ore deposits Black sand Placer mining Drift mining Sedimentology
35.
Alluvial fan
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An alluvial fan is a fan- or cone-shaped deposit of sediment crossed and built up by streams. If a fan is built up by debris flows it is called a debris cone or colluvial fan. These flows come from a point source at the apex of the fan. Fans are typically found where a canyon draining from mountainous terrain emerges out onto a flatter plain, a convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial fan. As a streams gradient decreases, it drops coarse-grained material and this reduces the capacity of the channel and forces it to change direction and gradually build up a slightly mounded or shallow conical fan shape. The deposits are poorly sorted. There will be iso-transport energy lines forming concentric arcs about the point at the apex of the fan. Thus the material will tend to be deposited equally about these lines, Alluvial fans are often found in desert areas subject to periodic flash floods from nearby thunderstorms in local hills. The typical watercourse in an arid climate has a large, funnel-shaped basin at the top, leading to a narrow defile, multiple braided streams are usually present and active during water flows. Phreatophytes are plants that are concentrated at the base of alluvial fans. They have long tap roots 30 to 50 feet to water that has seeped through the fan and hit an impermeable layer, sometimes collecting in springs. These stands of shrubs cling to the soil at their bases, Alluvial fans also develop in wetter climates. Along the upper Koshi tributaries, tectonic forces elevate the Himalayas several millimeters annually, uplift is approximately in equilibrium with erosion, so the river annually carries some 100 million cubic meters of sediment as it exits the mountains. Deposition of this magnitude over millions of years is more than sufficient to account for the megafan, despite overpopulation on the plains, this bhabar zone is highly malarial and has remained largely uninhabited. In North America, streams flowing into Californias Central Valley have deposited smaller, such as that of the Kings River flowing out of the Sierra Nevada creates a low divide, turning the south end of the San Joaquin Valley into an endorheic basin without a connection to the ocean. Alluvial fans are subject to flooding and can be more dangerous than the upstream canyons that feed them. Their slightly convex perpendicular surfaces cause water to spread widely until there is no zone of refuge, if the gradient is steep, active transport of materials down the fan creates a moving substrate that is inhospitable to travel on foot or wheels. But as the gradient diminishes downslope, water comes down from above faster than it can flow away downstream, in the case of the Koshi River, the huge sediment load and megafans slightly convex transverse surface conspire against engineering efforts to contain peak flows inside manmade embankments
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Bay mud
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Bay mud manifests low shear strength, high compressibility and low permeability, making it hazardous to build upon in seismically active regions like the San Francisco Bay Area. Typical bulk density of bay mud is approximately 1.3 grams per cubic centimetre, Bay mud has its own official geological abbreviation. The designation for Quaternary older bay mud is Qobm and the acronym for Quaternary younger bay mud is Qybm, an alluvial layer is often found overlying the older bay mud. In relation to shipping channels, it is necessary to dredge bay bottoms. It is not uncommon to dredge the same channel repeatedly since further settling sediments are prone to redeposit on an open valley floor. Bay muds originate from two generalized sources, first alluvial deposits of clays, silts and sand occur from streams tributary to a given bay. The extent of these unconsolidated interglacial deposits typically ranges throughout a given bay to the extent of the historical perimeter marshlands, second, in periods of high glaciation, deposits of silts, sands and organic plus inorganic detritus may form a separate distinct layer. Thus bay muds are important time records of activity and streamflow throughout the Quaternary period. Some depositional formation is quite recent, such as in the case of Florida Bay, where much of the bay mud has accumulated since 2000 BC, and consists of primarily decayed organic material. In the case of the Bristol Channel in the United Kingdom bay, mud formation has been occurring at least since the Eemian Stage, in other cases such as with San Francisco Bay, deposition has been interrupted by sea-level changes, and strata of vastly different vintages are found. In the San Francisco Bay Area, these are called Young bay mud, human activities can also affect deposition, close to half of the Young Bay Mud in San Francisco Bay was placed in the period 1855–1865, as a result of placer mining in the Sierra Nevada foothills. Construction on bay mud sites is difficult because of the low strength. A number of buildings have been constructed over bay muds, typically employing special mitigation designs to withstand seismic risks. Complicating design issues, fill is sometimes deposited on the surface level. For example, the Dakin Building in Brisbane, California was designed in 1985 to sit on piles 150 feet deep, anchoring to the Franciscan formation, below the bay muds and through an upper fill layer. Furthermore, the entrance ramp has been set on a giant hinge to allow the surrounding land to settle, while the building absolute height remains constant. The Crowne Plaza high-rise hotel in Burlingame, California was also designed to sit over bay muds, as was the Westin Hotel in Millbrae, California, indeed, Bostons entire Back Bay district is named for the tidal bay that it now covers. Logan International Airport and the San Francisco International Airport are also constructed over bay mud, when the mud layer is exposed at the tidal fringe, mudflats result affording a unique ecotone that affords numerous shorebird species a safe feeding and resting habitat
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Braided stream
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Not to be confused with the River Braid, Ballymena, Northern Ireland. Braided streams occur in rivers with high slope and/or large sediment load, braided channels are also typical of environments that dramatically decrease channel depth, and consequently channel velocity, such as river deltas, alluvial fans and peneplains. Braided rivers, as distinct from meandering rivers, occur when a level of sediment load or slope is reached whilst a steep gradient is also maintained. A threshold slope was experimentally determined to be 0.016 for a 0.15 cu ft/s stream with poorly sorted coarse sand. Any slope over this threshold created a stream, while any slope under the threshold created a meandering stream or— for very low slopes—a straight channel. Also important to development is the proportion of suspended load sediment to bed load. The channels and braid bars are highly mobile, with the river layout often changing significantly during flood events. Channels move sideways via differential velocity, On the outside of a curve, deeper, swift water picks up sediment, the braided channels may flow within an area defined by relatively stable banks or may occupy an entire valley floor. The Rakaia River in Canterbury, New Zealand has cut a channel 100 metres wide into the surrounding plains, extensive braided river systems are found in Alaska, Canada, New Zealands South Island, and the Himalayas, which all contain young, rapidly eroding mountains. The enormous Brahmaputra-Jamuna River in Asia is an example of a braided river. Braided river systems are present in Africa, for example in the Touat Valley, a notable example of a large braided stream in the contiguous United States is the Platte River in central and western Nebraska. The sediment of the arid Great Plains is augmented by the presence of the nearby Sandhills region north of the river, a portion of the lower Yellow River takes a braided form. Others have interpreted the depositional environment for this unit as a tidal delta, ait Anabranch Lagoon Shoal Hibbert, Barry, Brown, Kerry, eds
38.
Desert pavement
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A desert pavement, also called reg, serir, gibber, or saï is a desert surface covered with closely packed, interlocking angular or rounded rock fragments of pebble and cobble size. Desert varnish collects on the surface rocks over time. Geologists debate the mechanics of pavement formation and their age, several theories have been proposed for the formation of desert pavements. A common theory suggests they form through the removal of sand, dust and other fine-grained material by the wind and intermittent rain. The removal of particles by wind does not continue indefinitely, because once the pavement forms. The small particles collect underneath the pavement surface, forming a vesicular A soil horizon, a newer theory of pavement formation comes from studies of places such as Cima Dome, in the Mojave Desert of California, by Stephen Wells and his coworkers. At Cima Dome, geologically recent lava flows are covered by younger layers, with desert pavement on top of them. The soil has built up, not blown away, yet the stones remain on top. There are no stones in the soil, not even gravel, researchers can determine how many years a stone has been exposed on the ground. Wells used a method based on cosmogenic helium-3, which forms by cosmic ray bombardment at the ground surface, helium-3 is retained inside grains of olivine and pyroxene in the lava flows, building up with exposure time. The helium-3 dates show that the stones in the desert pavement at Cima Dome have all been at the surface the same amount of time as the solid lava flows right next to them. He wrote in a July 1995 article in Geology, that he concluded, while the stones remain on the surface due to heave, deposition of windblown dust must build up the soil beneath that pavement. For the geologist, this means that some desert pavements preserve a long history of dust deposition beneath them. The dust is a record of ancient climate, just as it is on the sea floor. Desert pavement surfaces are coated with desert varnish, a dark brown. In the USA a famous example can be found on Newspaper Rock in southeastern Utah, Desert varnish is a thin coating of manganese, iron and clays on the surface of sun-baked boulders. It is formed by colonies of bacteria living on the surface for thousands of years. Desert varnish is also prevalent in the Mojave desert and Great Basin geomorphic province, stony deserts may be known by different names according to the region
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Diluvium
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The term was formerly given to the boulder clay deposits, supposed to have been caused by the Noachian deluge. The term diluvium in the meaning of A. N. Rudoy has become accepted, nearly all intermountain depressions in southern Siberia and northern Mongolia hosted glacier-dammed lakes during the Pleistocene ice ages. Climatic changes and hydrostatic alterations of the ice dams were followed by repeated fillings, the lake outbursts had a cataclysmic character. In accordance with conditions, the glaciers would protrude again into the main drainage valleys immediately after dam deformations and lake outbursts. The greatest of the lakes achieved volumes up to hundreds of cubic kilometres and these floods transformed the drainage valleys, repeatedly building new sediment deposits. The dating of the latter proves the occurrence of floods in the Chuya. During that period there were at least five large-scale flooding events, enormous water masses were drained simultaneously and repeatedly toward the south of West Siberia. The total water volume out of the Altai basins only used to reach 10 thousand cubic kilometres, with some periodicity, all of the basins of South Siberia were able to deliver northwards about 60 thousand cubic kilometres of flood waters. Alluvium Altai flood Channeled Scablands Colluvium Eluvium Giant current ripples Illuvium Chuya Flood Video Rudoy, glacier-dammed lakes and geological work of glacial superfloods in the Late Pleistocene, Southern Siberia, Altai Mountains, Quaternary International,2002, Vol. 87/1, pp. 119-140. Ice-dammed lakes and glacial debris super-flows in the Altay and the Sayan Mountains in late Wurm, Новые результаты моделирования гидравлических характеристик дилювиальных потоков из позднечетвертичного Чуйско-Курайского ледниково-подпрудного озера. Diluvium Video Athabasca-video in large Scale Alexei Rudoy, Giant gravel bars - дилювиально-аккумулятивные валы. Glacial Lakes and Glacial Lake Outburst Floods in Nepal, - International Centre for Integrated Mountain Development, Kathmandu, March 2011
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United States Department of Agriculture
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Approximately 80% of USDAs $140 billion budget goes to the Food and Nutrition Service program. The largest component of the FNS budget is the Supplemental Nutrition Assistance Program, after the resignation of Thomas Vilsack on January 13,2017 and the departure of President Barack Obama from office on January 20,2017, the acting Secretary of Agriculture is Michael Young. Activities in this include the Supplemental Nutrition Assistance Program, which provides healthy food to over 40 million low-income. The USDA also is concerned with assisting farmers and food producers with the sale of crops and it plays a role in overseas aid programs by providing surplus foods to developing countries. This aid can go through USAID, foreign governments, international bodies such as World Food Program, the Agricultural Act of 1949, section 416 and Agricultural Trade Development and Assistance Act of 1954, also known as Food for Peace, provides the legal basis of such actions. The USDA is a partner of the World Cocoa Foundation, early in its history, the economy of the United States was largely agrarian. Officials in the government had long sought new and improved varieties of seeds, plants. In 1837 Henry Leavitt Ellsworth, a Yale-educated attorney interested in improving agriculture, became Commissioner of Patents and he began collecting and distributing new varieties of seeds and plants through members of the Congress and agricultural societies. In 1839, Congress established the Agricultural Division within the Patent Office and allotted $1,000 for the collection of agricultural statistics, Ellsworth was called the Father of the Department of Agriculture. In 1849, the Patent Office was transferred to the newly created Department of the Interior, in the ensuing years, agitation for a separate bureau of agriculture within the department or a separate department devoted to agriculture kept recurring. Lincoln called it the peoples department, in the 1880s, varied advocacy groups were lobbying for Cabinet representation. Business interests sought a Department of Commerce and Industry, and farmers tried to raise the Department of Agriculture to Cabinet rank, finally, on February 9,1889, President Grover Cleveland signed a bill into law elevating the Department of Agriculture to Cabinet level. In 1887, the Hatch Act provided for the funding of agricultural experiment stations in each state. The Smith-Lever Act of 1914 then funded cooperative extension services in each state to teach agriculture, home economics, with these and similar provisions, the USDA reached out to every county of every state. During the Great Depression, farming remained a way of life for millions of Americans. The Department of Agricultures Bureau of Home Economics, established in 1923, published shopping advice and recipes to stretch family budgets and make food go farther. USDA helped ensure that continued to be produced and distributed to those who needed it, assisted with loans for small landowners. The Department of Agriculture was authorized a budget for Fiscal Year 2015 of $139.7 billion, the Washington Post reports that he said There are days when I have literally nothing to do, he recalled thinking as he weighed his decision to quit
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United States Geological Survey
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The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its resources. The organization has four science disciplines, concerning biology, geography, geology. The USGS is a research organization with no regulatory responsibility. The USGS is a bureau of the United States Department of the Interior, the USGS employs approximately 8,670 people and is headquartered in Reston, Virginia. The USGS also has major offices near Lakewood, Colorado, at the Denver Federal Center, the current motto of the USGS, in use since August 1997, is science for a changing world. The agencys previous slogan, adopted on the occasion of its anniversary, was Earth Science in the Public Service. Prompted by a report from the National Academy of Sciences, the USGS was created, by a last-minute amendment and it was charged with the classification of the public lands, and examination of the geological structure, mineral resources, and products of the national domain. This task was driven by the need to inventory the vast lands added to the United States by the Louisiana Purchase in 1803, the legislation also provided that the Hayden, Powell, and Wheeler surveys be discontinued as of June 30,1879. Clarence King, the first director of USGS, assembled the new organization from disparate regional survey agencies, after a short tenure, King was succeeded in the directors chair by John Wesley Powell. Administratively, it is divided into a Headquarters unit and six Regional Units, Other specific programs include, Earthquake Hazards Program monitors earthquake activity worldwide. The National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location, the USGS also runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System. The USGS informs authorities, emergency responders, the media, and it also maintains long-term archives of earthquake data for scientific and engineering research. It also conducts and supports research on long-term seismic hazards, USGS has released the UCERF California earthquake forecast. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time, the USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online, since 1962, the Astrogeology Research Program has been involved in global, lunar, and planetary exploration and mapping. USGS operates a number of related programs, notably the National Streamflow Information Program. USGS Water data is available from their National Water Information System database
Chisholm, Hugh, ed. (1911). "Alluvium". Encyclopædia Britannica (11th ed.). Cambridge University Press.
Chisholm, Hugh, ed. (1911). "