A valley is a low area between hills, often with a river running through it. In geology, a valley or dale is a depression that is longer than it is wide, the terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys. Most valleys belong to one of two main types or a mixture of them, with respect to the cross section of the slopes or hillsides. A valley in its broadest geographic sense is known as a dale. A valley through which a river runs may be referred to as a vale, a small and often wooded valley is known as a dell or in Scotland as a glen. A wide, flat valley through which a river runs is known in Scotland as a strath, a mountain cove is a small valley, closed at one or both ends, in the central or southern Appalachian Mountains which sometimes results from the erosion of a geologic window. A small valley surrounded by mountains or ridges is sometimes known as a hollow, a deep, narrow valley is known as a cwm. Similar geological structures, such as canyons, gorges, chines, a valley formed by erosion is called an erosional valley, a valley formed by geologic events such as drop faults or the rise of highlands is called a structural valley. A valley formed by flowing water, or river valley, is usually V-shaped, the exact shape will depend on the characteristics of the stream flowing through it.
Rivers with steep gradients, as in mountain ranges, produce steep walls, shallower slopes may produce broader and gentler valleys. However, in the lowest stretch of a river, where it approaches its base level, it begins to deposit sediment, in prehistory, the rivers were used as a source of fresh water and food, as well as a place to wash and a sewer. The proximity of water moderated temperature extremes and provided a source for irrigation, most of the first civilizations developed from these river valley communities. In geography, a vale is a river valley, usually with a particularly wide flood plain or flat valley bottom. In Southern England, vales commonly occur between the escarpment slopes of pairs of chalk formations, where the dome has been eroded, exposing less resistant underlying rock. Rift valleys, such as the Albertine Rift, are formed by the expansion of the Earths crust due to tectonic activity beneath the Earths surface, there are various forms of valley associated with glaciation that may be referred to as glacial valleys. A valley carved by glaciers is normally U-shaped, the valley becomes visible upon the recession of the glacier that forms it.
When the ice recedes or thaws, the remains, often littered with small boulders that were transported within the ice. Floor gradient does not affect the shape, it is the glaciers size that does
Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers to its solid state or its gaseous state. It occurs in nature as snow, ice packs and icebergs, fog, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are chemically combined or adsorbed in hydrated minerals.
Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, lakes, large quantities of water and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life.
Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
Colombia, officially the Republic of Colombia, is a transcontinental country largely situated in the northwest of South America, with territories in Central America. Colombia shares a border to the northwest with Panama, to the east with Venezuela and Brazil and to the south with Ecuador and it shares its maritime limits with Costa Rica, Honduras, Jamaica and the Dominican Republic. It is a unitary, constitutional republic comprising thirty-two departments, the territory of what is now Colombia was originally inhabited by indigenous peoples including the Muisca, the Quimbaya and the Tairona. The Spanish arrived in 1499 and initiated a period of conquest and colonization ultimately creating the Viceroyalty of New Granada, independence from Spain was won in 1819, but by 1830 the Gran Colombia Federation was dissolved. What is now Colombia and Panama emerged as the Republic of New Granada, the new nation experimented with federalism as the Granadine Confederation, and the United States of Colombia, before the Republic of Colombia was finally declared in 1886.
Since the 1960s the country has suffered from an asymmetric low-intensity armed conflict, Colombia is one of the most ethnically and linguistically diverse countries in the world, and thereby possesses a rich cultural heritage. Cultural diversity has influenced by Colombias varied geography. The urban centres are located in the highlands of the Andes mountains. Colombian territory encompasses Amazon rainforest, tropical grassland and both Caribbean and Pacific coastlines, ecologically, it is one of the worlds 17 megadiverse countries, and the most densely biodiverse of these per square kilometer. Colombia is a power and a regional actor with the fourth-largest economy in Latin America, is part of the CIVETS group of six leading emerging markets and is an accessing member to the OECD. Colombia has an economy with macroeconomic stability and favorable growth prospects in the long run. The name Colombia is derived from the last name of Christopher Columbus and it was conceived by the Venezuelan revolutionary Francisco de Miranda as a reference to all the New World, but especially to those portions under Spanish and Portuguese rule.
The name was adopted by the Republic of Colombia of 1819. When Venezuela and Cundinamarca came to exist as independent states, New Granada officially changed its name in 1858 to the Granadine Confederation. In 1863 the name was changed, this time to United States of Colombia. To refer to country, the Colombian government uses the terms Colombia. Owing to its location, the present territory of Colombia was a corridor of early human migration from Mesoamerica, the oldest archaeological finds are from the Pubenza and El Totumo sites in the Magdalena Valley 100 km southwest of Bogotá. These sites date from the Paleoindian period, at Puerto Hormiga and other sites, traces from the Archaic Period have been found
1980 eruption of Mount St. Helens
On May 18,1980, a major volcanic eruption occurred at Mount St. Helens, a volcano located in Skamania County, in the state of Washington, United States. The eruption was the significant volcanic eruption to occur in the contiguous 48 U. S. states since the 1915 eruption of Lassen Peak in California. However, it has often declared as the most disastrous volcanic eruption in United States history. An earthquake at 8,32,17 a. m. PDT on Sunday, May 18,1980, caused the entire weakened north face to slide away, creating the largest landslide ever recorded. An eruption column rose 80,000 feet into the atmosphere, at the same time, snow and several entire glaciers on the volcano melted, forming a series of large lahars that reached as far as the Columbia River, nearly 50 miles to the southwest. Less severe outbursts continued into the day, only to be followed by other large. Approximately fifty-seven people were killed directly, including innkeeper Harry R. Truman, photographer Reid Blackburn and geologist David A.
Johnston. Hundreds of square miles were reduced to wasteland, causing over a billion U. S. dollars in damage, thousands of animals were killed. At the time of the eruption, the summit of the volcano was owned by the Burlington Northern Railroad, the area was preserved, as it was, in the Mount St. Helens National Volcanic Monument. Mount St. Helens remained dormant from its last period of activity in the 1840s and 1850s until March 1980, several small earthquakes, apparently beginning on March 15, indicated that magma may have begun moving below the volcano. Then on March 20, at 3,45 p. m. Pacific Standard Time, a total of 174 shocks of magnitude 2.6 or greater were recorded during those two days. Initially there was no sign of eruption, but small earthquake-induced avalanches of snow. At 12,36 p. m. on March 27, phreatic eruptions ejected and smashed rock from within the old crater, excavating a new crater 250 feet wide. By this date a 16, 000-foot long eastward-trending fracture system had developed across the summit area.
This was followed by more earthquake swarms and a series of explosions that sent ash 10,000 to 11,000 feet above their vent. Most of this ash fell between 3 and 12 miles from its vent, but some was carried 150 miles south to Bend, Oregon, or 285 miles east to Spokane, a second, new crater and a blue flame were observed on March 29. The flame was visibly emitted from both craters and was created by burning gases. Static electricity generated from ash clouds rolling down the volcano sent out lightning bolts that were up to 2 miles long
United States Geological Survey
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, 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 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 provided that the Hayden 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 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 maintains long-term archives of earthquake data for scientific and engineering research.
It 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 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
The Armero tragedy was one of the major consequences of the eruption of the Nevado del Ruiz stratovolcano in Tolima, Colombia, on November 13,1985. As pyroclastic flows erupted from the crater, they melted the mountains glaciers. The lahars picked up speed in gullies and coursed into the six major rivers at the base of the volcano, they engulfed the town of Armero, casualties in other towns, particularly Chinchiná, brought the overall death toll to 23,000. Footage and photographs of Omayra Sánchez, a victim of the tragedy, were published around the world. Other photographs of the lahars and the impact of the disaster captured attention worldwide, a banner at a mass funeral in Ibagué read, The volcano didnt kill 22,000 people. The relief efforts were hindered by the composition of the mud, by the time relief workers reached Armero twelve hours after the eruption, many of the victims with serious injuries were dead. The relief workers were horrified by the landscape of trees, disfigured human bodies.
This was the second-deadliest volcanic disaster of the 20th century, surpassed only by the 1902 eruption of Mount Pelée, Hazard maps for the vicinity were prepared, but poorly distributed. On the day of the eruption, several attempts were made. Many victims stayed in their houses as they had been instructed, the noise from the storm may have prevented many from hearing the sounds from Ruiz until it was too late. Nevado del Ruiz has erupted several times since the disaster, and continues to threaten up to 500,000 people living along the Combeima, Coello-Toche, and Guali river valleys. A lahar similar in size to the 1985 event could potentially travel as far as 100 kilometers from the volcano, to counter this threat, the Colombian government established a specialized office which promotes awareness of natural threats. Additionally, many of Colombias cities have programs to awareness of natural disaster planning programs which have helped save lives in natural disasters. Near Nevado del Ruiz in particular, locals have become wary of volcanic activity, located 48 kilometers from the Nevado del Ruiz volcano and 169 kilometers from Colombias capital of Bogotá, was the third largest town in Tolima Department, after Ibagué and Espinal.
A prominent farming town before the eruption, it was responsible for roughly one-fifth of Colombias rice production, and for a share of the cotton, sorghum. Much of this success can be attributed to Nevado del Ruiz, built on top of an alluvial fan that had been host to historic lahars, the town was previously destroyed by a volcanic eruption in 1595 and by mudflows in 1845. In the 1595 eruption, three distinct Plinian eruptions produced lahars that claimed the lives of 636 people, during the 1845 event,1,000 people were killed by earthquake-generated mudflows near the Magdalena River. Nevado del Ruiz has undergone three distinct periods, the first beginning 1.8 million years ago
A flood is an overflow of water that submerges land which is usually dry. The European Union Floods Directive defines a flood as a covering by water of land not normally covered by water, in the sense of flowing water, the word may be applied to the inflow of the tide. Floods can occur in rivers when the flow exceeds the capacity of the river channel. Floods often cause damage to homes and businesses if they are in the flood plains of rivers. Some floods develop slowly, while others such as floods, can develop in just a few minutes. Additionally, floods can be local, impacting a neighborhood or community, or very large, the word flood comes from the Old English flod, a word common to Germanic languages. Deluge myths are stories of a great flood sent by a deity or deities to destroy civilization as an act of divine retribution. Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths, surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms.
Infiltration is slow to negligible through frozen ground, concrete, areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience flooding during periods when precipitation exceeds evaporation. Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the worlds largest rivers. When overland flow occurs on tilled fields, it can result in a flood where sediments are picked up by run off. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, debris, slow-rising floods most commonly occur in large rivers with large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, the cause may be localized convective precipitation or sudden release from an upstream impoundment created behind a dam, landslide, or glacier.
In one instance, a flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Without any observed rainfall, the rate increased from about 50 to 1,500 cubic feet per second in just one minute. Two larger floods occurred at the site within a week
Nevado del Ruiz
It is a stratovolcano, composed of many layers of lava alternating with hardened volcanic ash and other pyroclastic rocks. Nevado del Ruiz has been active for two million years, since the early Pleistocene or late Pliocene epoch, with three major eruptive periods. The current volcanic cone formed during the present eruptive period, which began 150 thousand years ago, the volcano usually generates Plinian eruptions, which produce swift-moving currents of hot gas and rock called pyroclastic flows. These eruptions often cause massive lahars, which pose a threat to human life, the impact of such an eruption is increased as the hot gas and lava melt the mountains snowcap, adding large quantities of water to the flow. On November 13,1985, a small eruption produced an enormous lahar that buried and destroyed the town of Armero in Tolima and this event became known as the Armero tragedy—the deadliest lahar in recorded history. Similar but less deadly incidents occurred in 1595 and 1845, consisting of an explosive eruption followed by a large lahar.
The volcano is part of Los Nevados National Natural Park, which contains several other volcanoes. The summit of Nevado del Ruiz is covered by large glaciers, the volcano continues to pose a threat to the nearby towns and villages, and it is estimated that up to 500,000 people could be at risk from lahars from future eruptions. Nevado del Ruiz, which lies about 129 kilometers west of Bogotá, is part of the Andes mountain range, the volcano is part of the Ruiz–Tolima volcanic massif, a group of five ice-capped volcanoes which includes the Tolima, Santa Isabel and Machin volcanoes. The massif is located at the intersection of four faults, some of which still are active, Nevado del Ruiz lies within the Pacific Ring of Fire, a region that encircles the Pacific Ocean and contains some of the worlds most active volcanoes. It is the third most northerly of the lying in the North Volcanic Zone of the Andean Volcanic Belt. The Andean Volcanic Belt is produced by the subduction of the oceanic Nazca Plate beneath the South American continental plate.
Like many other Andean volcanoes, Nevado del Ruiz is a stratovolcano and its lavas are andesitic–dacitic in composition. It covers an area of more than 200 square kilometers, stretching 65 kilometers from east to west, the mountains broad summit includes the Arenas crater, which is one kilometer in diameter and 240 meters deep. The summit of the volcano has steep slopes inclining from 20 to 30 degrees, at lower elevations, the slopes become less steep, their inclination is about 10 degrees. From there on, foothills stretch almost to the edge of the Magdalena River north of the volcano, on the two major sides of the summit, headwalls show where past rock avalanches occurred. At times, ice on the summit has melted, generating devastating lahars, on the volcanos southwest flank is the pyroclastic cone La Olleta, which is not currently active, but may have erupted in historical times. The summit of Nevado del Ruiz is covered by glaciers, which formed many thousands of years
A glacier is a persistent body of dense ice that is constantly moving under its own weight, it forms where the accumulation of snow exceeds its ablation over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses and they abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice, between 35°N and 35°S, glaciers occur only in the Himalayas, Rocky Mountains, a few high mountains in East Africa, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earths land surface, continental glaciers cover nearly 13,000,000 km2 or about 98 percent of Antarcticas 13,200,000 km2, with an average thickness of 2,100 m. Greenland and Patagonia have huge expanses of continental glaciers, Glacial ice is the largest reservoir of fresh water on Earth. Within high altitude and Antarctic environments, the temperature difference is often not sufficient to release meltwater. A large piece of compressed ice, or a glacier, appears blue as large quantities of water appear blue and this is because water molecules absorb other colors more efficiently than blue.
The other reason for the color of glaciers is the lack of air bubbles. Air bubbles, which give a color to ice, are squeezed out by pressure increasing the density of the created ice. The word Glaceon is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, the processes and features caused by or related to glaciers are referred to as glacial. The process of establishment and flow is called glaciation. The corresponding area of study is called glaciology, Glaciers are important components of the global cryosphere. Glaciers are categorized by their morphology, thermal characteristics, and behavior, cirque glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier, a large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have a less than 50,000 km2 by definition. Glacial bodies larger than 50,000 km2 are called ice sheets or continental glaciers, several kilometers deep, they obscure the underlying topography.
Only nunataks protrude from their surfaces, the only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of water, enough that if both melted, global sea levels would rise by over 70 m
Pierce County, Washington
Pierce County is a county in the U. S. state of Washington. As of the 2010 Census, the population was 795,225, the county seat and largest city is Tacoma. Formed out of Thurston County on December 22,1852, by the legislature of Oregon Territory, Pierce County is in the Seattle metropolitan area. Pierce County is notable for being home to Mount Rainier, the tallest mountain and its most recent recorded eruption was between 1820 and 1854. There is no imminent risk of eruption, but geologists expect that the volcano will erupt again, if this should happen, parts of Pierce County and the Puyallup Valley would be at risk from lahars, lava, or pyroclastic flows. The Mount Rainier Volcano Lahar Warning System was established in 1998 to assist in the evacuation of the Puyallup River valley in case of eruption. According to the U. S. Census Bureau, the county has an area of 1,806 square miles. The highest natural point in Washington, Mount Rainier at 14,410 feet, is located in Pierce County, Pierce County contains the Clearwater Wilderness area.
The population density was 417 people per square mile, there were 277,060 housing units at an average density of 165 per square mile. The racial makeup of the county was 78. 39% White,6. 95% Black or African American,1. 42% Native American,5. 08% Asian,0. 85% Pacific Islander,2. 20% from other races, and 5. 11% from two or more races. 5. 51% of the population were Hispanic or Latino of any race,16. 1% were of German,8. 6% Irish,8. 2% English,6. 3% United States or American and 6. 2% Norwegian ancestry according to the 2000 census. 24. 30% of all households were made up of individuals and 7. 60% had someone living alone who was 65 years of age or older, the average household size was 2.60 and the average family size was 3.10. In the county, the population was out with 27. 20% under the age of 18,9. 80% from 18 to 24,31. 30% from 25 to 44,21. 50% from 45 to 64. The median age was 34 years, for every 100 females there were 98.90 males. For every 100 females age 18 and over, there were 96.70 males, the median income for a household in the county was $45,204, and the median income for a family was $52,098.
Males had an income of $38,510 versus $28,580 for females. The per capita income for the county was $20,948, about 7. 50% of families and 10. 50% of the population were below the poverty line, including 13. 20% of those under age 18 and 7. 20% of those age 65 or over. As of the 2010 United States Census, there were 795,225 people,299,918 households, the population density was 476.3 inhabitants per square mile
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earths volcanoes occur because its crust is broken into 17 major, therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. This type of volcanism falls under the umbrella of plate hypothesis volcanism, Volcanism away from plate boundaries has been explained as mantle plumes. These so-called hotspots, for example Hawaii, are postulated to arise from upwelling diapirs with magma from the boundary,3,000 km deep in the Earth. Volcanoes are usually not created where two plates slide past one another. Erupting volcanoes can pose hazards, not only in the immediate vicinity of the eruption. Historically, so-called volcanic winters have caused catastrophic famines, the word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology.
The study of volcanoes is called volcanology, sometimes spelled vulcanology, at the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. Most divergent plate boundaries are at the bottom of the oceans, most volcanic activity is submarine, black smokers are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the temperature of the overlying mantle wedge. This magma tends to be very viscous due to its high content, so it often does not reach the surface. When it does reach the surface, a volcano is formed, typical examples of this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire.
Because tectonic plates move across them, each volcano becomes dormant and is eventually re-formed as the plate advances over the postulated plume and this theory is currently under criticism, however. The most common perception of a volcano is of a mountain, spewing lava and poisonous gases from a crater at its summit, however. The features of volcanoes are more complicated and their structure. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have features such as massive plateaus