1.
Lake Parinacochas
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Lake Parinacochas is a lake in Ayacucho Region in Peru. It is located west of Sara Sara volcano at an elevation of 3,272 metres above sea level, the lake is 12 km long and 9 km wide, and has a catchment area of 606.5 square kilometres. Lake Parinacochas is a brackish lake, with some salt pan areas appearing at low water levels. The lake is located in a dry puna grassland region, aquatic vegetation is represented by reeds of Typha sp. and submerged plants of genus Potamogeton. Sara Sara List of lakes in Peru
2.
Summit
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A summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. Mathematically, a summit is a maximum in elevation. The topographic terms acme, apex, peak, and zenith are synonymous, the UIAA definition is that a summit is independent if it has a prominence of 30 metres or more, it is a mountain if it has a prominence of at least 300 metres. This can be summarised as follows, A pyramidal peak is an exaggerated form produced by ice erosion of a mountain top, Summit may also refer to the highest point along a line, trail, or route. In many parts of the western United States, the term refers to the highest point along a road, highway. For example, the highest point along Interstate 80 in California is referred to as Donner Summit while the highest point on Interstate 5 is Siskiyou Mountain Summit, geoid Hill List of highest mountains Maxima and minima Nadir Summit accordance Peak finder
3.
Topographic prominence
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It is a measure of the independence of a summit. A peaks key col is a point on this contour line. By convention, the prominence of Mount Everest, the Earths highest mountain, is taken to equal the elevation of its summit above sea level, if the peaks prominence is P metres, to get from the summit to any higher terrain one must descend at least P metres. Together with the convention for Mount Everest, this implies that the prominence of any island or continental highpoint is equal to its elevation above sea level, for every ridge connecting the peak to higher terrain, find the lowest point on the ridge. The key col is defined as the highest of these cols, the prominence is the difference between the elevation of the peak and the elevation of the key col. The following mental exercise may illustrate the meaning of topographic prominence, imagine you are standing at the top of a peak and imagine that an imaginary sea level rises to your feet. Now slowly lower the sea level and an imaginary island appears beneath your feet. Your island will grow and will merge with other islands that emerge, the parent peak may be either close or far from the subject peak. The summit of Mount Everest is the parent peak of Aconcagua at a distance of 17,755 km, the key col may also be close or far from the subject peak. The key col for Aconcagua is the Bering Strait at a distance of 13,655 km, the key col for the South Summit of Mount Everest is about 100 m distant. Prominence is interesting to many mountaineers because it is a measurement that is strongly correlated with the subjective significance of a summit. Peaks with low prominences are either subsidiary tops of some higher summit or relatively insignificant independent summits, peaks with high prominences tend to be the highest points around and are likely to have extraordinary views. Only summits with a sufficient degree of prominence are regarded as independent mountains, for example, the worlds second-highest mountain is K2. While Mount Everests South Summit is taller than K2, it is not considered an independent mountain because it is a subsummit of the main summit, many lists of mountains take topographic prominence as a criterion for inclusion, or cutoff. John and Anne Nuttalls The Mountains of England and Wales uses a cutoff of 15 m, in the contiguous United States, the famous list of fourteeners uses a cutoff of 300 ft /91 m. Also in the U. S.2000 feet of prominence has become a threshold that signifies that a peak has major stature. This generates lists of peaks ranked by prominence, which are different from lists ranked by elevation. Such lists tend to emphasize isolated high peaks, such as range or island high points, one advantage of a prominence-ranked list is that it needs no cutoff, since a peak with high prominence is automatically an independent peak
4.
Ultra-prominent peak
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An ultra-prominent peak, or Ultra for short, is defined as a mountain summit with a topographic prominence of 1,500 metres or more. There are approximately 1,524 such peaks on Earth, some peaks, such as the Matterhorn and Eiger, are not Ultras because they are connected to higher mountains by high cols and therefore do not achieve enough topographic prominence. The term Ultra is due to earth scientist Stephen Fry, from his studies of the prominence of peaks in Washington in the 1980s and his original term was ultra major mountain, referring to peaks with at least 5,000 ft of prominence. Currently,1,515 Ultras have been identified worldwide,637 in Asia,355 in North America,209 in South America,119 in Europe,84 in Africa,69 in Australasia and 39 in Antarctica. Many of the worlds largest mountains are Ultras, including Mount Everest, K2, Kilimanjaro, Mont Blanc, on the other hand, others such as the Eiger and the Matterhorn are not Ultras because they do not have sufficient prominence. In British Columbia, some of the mountains listed do not even have generally recognized names, a number of Ultras have yet to be climbed, with Sauyr Zhotasy, Mount Siple, and Gangkar Puensum being the most likely candidates for the most prominent unclimbed mountain in the world. All of the Seven Summits are Ultras by virtue of the fact that they are the points of large landmasses. Each has its key col at or near sea level, resulting in a value almost equal to its elevation. List of peaks by prominence gives the 125 most prominent peaks worldwide
5.
Geographic coordinate system
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A geographic coordinate system is a coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are chosen such that one of the numbers represents a vertical position. A common choice of coordinates is latitude, longitude and elevation, to specify a location on a two-dimensional map requires a map projection. The invention of a coordinate system is generally credited to Eratosthenes of Cyrene. Ptolemy credited him with the adoption of longitude and latitude. Ptolemys 2nd-century Geography used the prime meridian but measured latitude from the equator instead. Mathematical cartography resumed in Europe following Maximus Planudes recovery of Ptolemys text a little before 1300, in 1884, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, the Dominican Republic voted against the motion, while France and Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911, the latitude of a point on Earths surface is the angle between the equatorial plane and the straight line that passes through that point and through the center of the Earth. Lines joining points of the same latitude trace circles on the surface of Earth called parallels, as they are parallel to the equator, the north pole is 90° N, the south pole is 90° S. The 0° parallel of latitude is designated the equator, the plane of all geographic coordinate systems. The equator divides the globe into Northern and Southern Hemispheres, the longitude of a point on Earths surface is the angle east or west of a reference meridian to another meridian that passes through that point. All meridians are halves of great ellipses, which converge at the north and south poles, the prime meridian determines the proper Eastern and Western Hemispheres, although maps often divide these hemispheres further west in order to keep the Old World on a single side. The antipodal meridian of Greenwich is both 180°W and 180°E, the combination of these two components specifies the position of any location on the surface of Earth, without consideration of altitude or depth. The grid formed by lines of latitude and longitude is known as a graticule, the origin/zero point of this system is located in the Gulf of Guinea about 625 km south of Tema, Ghana. To completely specify a location of a feature on, in, or above Earth. Earth is not a sphere, but a shape approximating a biaxial ellipsoid. It is nearly spherical, but has an equatorial bulge making the radius at the equator about 0. 3% larger than the radius measured through the poles, the shorter axis approximately coincides with the axis of rotation
6.
Peru
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Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the west by the Pacific Ocean. Peruvian territory was home to ancient cultures spanning from the Norte Chico civilization in Caral, one of the oldest in the world, to the Inca Empire, the largest state in Pre-Columbian America. The Spanish Empire conquered the region in the 16th century and established a Viceroyalty with its capital in Lima, ideas of political autonomy later spread throughout Spanish America and Peru gained its independence, which was formally proclaimed in 1821. After the battle of Ayacucho, three years after proclamation, Peru ensured its independence, subsequently, the country has undergone changes in government from oligarchic to democratic systems. Peru has gone through periods of political unrest and internal conflict as well as periods of stability, Peru is a representative democratic republic divided into 25 regions. It is a country with a high Human Development Index score. Its main economic activities include mining, manufacturing, agriculture and fishing, the Peruvian population, estimated at 31.2 million in 2015, is multiethnic, including Amerindians, Europeans, Africans and Asians. The main spoken language is Spanish, although a significant number of Peruvians speak Quechua or other native languages and this mixture of cultural traditions has resulted in a wide diversity of expressions in fields such as art, cuisine, literature, and music. The name of the country may be derived from Birú, the name of a ruler who lived near the Bay of San Miguel, Panama. When his possessions were visited by Spanish explorers in 1522, they were the southernmost part of the New World yet known to Europeans, thus, when Francisco Pizarro explored the regions farther south, they came to be designated Birú or Perú. An alternative history is provided by the contemporary writer Inca Garcilasco de la Vega, son of an Inca princess, the Spanish Crown gave the name legal status with the 1529 Capitulación de Toledo, which designated the newly encountered Inca Empire as the province of Peru. Under Spanish rule, the country adopted the denomination Viceroyalty of Peru, the earliest evidences of human presence in Peruvian territory have been dated to approximately 9,000 BC. Andean societies were based on agriculture, using such as irrigation and terracing, camelid husbandry. Organization relied on reciprocity and redistribution because these societies had no notion of market or money, the oldest known complex society in Peru, the Norte Chico civilization, flourished along the coast of the Pacific Ocean between 3,000 and 1,800 BC. These early developments were followed by archaeological cultures that developed mostly around the coastal, the Cupisnique culture which flourished from around 1000 to 200 BC along what is now Perus Pacific Coast was an example of early pre-Incan culture. The Chavín culture that developed from 1500 to 300 BC was probably more of a religious than a political phenomenon, on the coast, these included the civilizations of the Paracas, Nazca, Wari, and the more outstanding Chimu and Mochica. Their capital was at Chan Chan outside of modern-day Trujillo, in the 15th century, the Incas emerged as a powerful state which, in the span of a century, formed the largest empire in pre-Columbian America with their capital in Cusco
7.
Ayacucho Region
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Ayacucho is a region of Peru, located in the south-central Andes of the country. Its capital is the city of Ayacucho, the region was one of the hardest hit by terrorism during the 1980s during the guerrilla war waged by Shining Path known as the internal conflict in Peru. The bill failed and Ayacucho remained an independent region, the region is divided into 11 provinces, which are composed of 111 districts. The Quechua variety spoken in Ayacucho is Chanka Quechua, the following table shows the results concerning the language learnt first in the Ayacucho Region by province, Ayacucho Regional Government official website
8.
Mountain range
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A mountain range is a geographic area containing numerous geologically related mountains. A mountain system or system of ranges, sometimes is used to combine several geological features that are geographically related. Mountain ranges are usually segmented by highlands or mountain passes and valleys, individual mountains within the same mountain range do not necessarily have the same geologic structure or petrology. They may be a mix of different orogenic expressions and terranes, for example thrust sheets, uplifted blocks, fold mountains, most geologically young mountain ranges on the Earths land surface are associated with either the Pacific Ring of Fire or the Alpide Belt. The Andes is 7,000 kilometres long and is considered the worlds longest mountain system. The Alpide belt includes Indonesia and southeast Asia, through the Himalaya, the belt also includes other European and Asian mountain ranges. The Himalayas contain the highest mountains in the world, including Mount Everest, mountain ranges outside of these two systems include the Arctic Cordillera, the Urals, the Appalachians, the Scandinavian Mountains, the Altai Mountains and the Hijaz Mountains. If the definition of a range is stretched to include underwater mountains. The mountain systems of the earth are characterized by a tree structure, the sub-range relationship is often expressed as a parent-child relationship. For example, the White Mountains of New Hampshire and the Blue Ridge Mountains are sub-ranges of the Appalachian Mountains, equivalently, the Appalachians are the parent of the White Mountains and Blue Ridge Mountains, and the White Mountains and the Blue Ridge Mountains are children of the Appalachians. The position of mountains influences climate, such as rain or snow, when air masses move up and over mountains, the air cools producing orographic precipitation. As the air descends on the side, it warms again and is drier. Often, a shadow will affect the leeward side of a range. Mountain ranges are constantly subjected to forces which work to tear them down. Erosion is at work while the mountains are being uplifted and long after until the mountains are reduced to low hills, rivers are traditionally believed to be the principle erosive factor on mountain ranges, with their ability of bedrock incision and sediment transport. The rugged topography of a range is the product of erosion. The basins adjacent to a mountain range are filled with sediments which are buried and turned into sedimentary rock. The early Cenozoic uplift of the Rocky Mountains of Colorado provides an example and this mass of rock was removed as the range was actively undergoing uplift
9.
Andes
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The Andes or Andean Mountains are the longest continental mountain range in the world. They are a range of highlands along the western edge of South America. This range is about 7,000 km long, about 200 to 700 km wide, the Andes extend from north to south through seven South American countries, Venezuela, Colombia, Ecuador, Peru, Bolivia, Argentina and Chile. Along their length, the Andes are split into several ranges, the Andes are the location of several high plateaus – some of which host major cities, such as Quito, Bogotá, Arequipa, Medellín, Sucre, Mérida and La Paz. The Altiplano plateau is the worlds second-highest after the Tibetan plateau and these ranges are in turn grouped into three major divisions based on climate, the Tropical Andes, the Dry Andes, and the Wet Andes. The Andes are the worlds highest mountain range outside of Asia, the highest mountain outside Asia, Mount Aconcagua, rises to an elevation of about 6,961 m above sea level. The peak of Chimborazo in the Ecuadorean Andes is farther from the Earths center than any other location on the Earths surface, the worlds highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina border, which rises to 6,893 m. The etymology of the word Andes has been debated, the majority consensus is that it derives from the Quechua word anti, which means east as in Antisuyu, one of the four regions of the Inca Empire. In the northern part of the Andes, the isolated Sierra Nevada de Santa Marta range is considered to be part of the Andes. The term cordillera comes from the Spanish word cordel, meaning rope, the Andes range is about 200 km wide throughout its length, except in the Bolivian flexure where it is about 640 kilometres wide. The Andes are the result of plate tectonics processes, caused by the subduction of oceanic crust beneath the South American plate. The main cause of the rise of the Andes is the compression of the rim of the South American Plate due to the subduction of the Nazca Plate. In the south, the Andes share a boundary with the former Patagonia Terrane. To the west, the Andes end at the Pacific Ocean, from a geographical approach, the Andes are considered to have their western boundaries marked by the appearance of coastal lowlands and a less rugged topography. The Andes Mountains also contain large quantities of iron ore located in mountains within the range. The Andean orogen has a series of bends or oroclines, the Bolivian Orocline is a seaward concave bending in the coast of South America and the Andes Mountains at about 18° S. At this point the orientation of the Andes turns from Northwest in Peru to South in Chile, the Andean segment north and south of the orocline have been rotated 15° to 20° counter clockwise and clockwise respectively. The Bolivian Orocline area overlaps with the area of maximum width of the Altiplano Plateau, the specific point at 18° S where the coastline bends is known as the Arica Elbow
10.
Parinacochas Province
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The Parinacochas Province is a province located in the Ayacucho Region of Peru. It is one of the eleven that make up that region, the province has a population of 24,028 inhabitants as of 2002. The capital of the province is Coracora, other mountains are listed below, The province extends over an area of 5,968. Quechua is the language which the majority of the population learnt to speak in childhood,44. 60% of the residents started speaking using the Spanish language
11.
Paucar del Sara Sara Province
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Paucar del Sara Sara Province is a province located in the south-eastern corner of the Ayacucho Region of Peru. It is one of provinces that make up the region. The province has a population of 10,610 inhabitants 2005 census and it is bounded to the north and west by the Parinacochas Province and to the south and east by the Arequipa Region. The capital of province is the city of Pausa. The highest mountain in the province is Sara Sara at 5,505 m on the border to the Parinacochas Province, other mountains are listed below, The province extends over an area of 2,096.92 square kilometres and is divided into ten districts. Quechua is the language which the majority of the population learnt to speak in childhood,49.36 % of the residents started speaking using the Spanish language
12.
Agriculture
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Agriculture is the cultivation and breeding of animals, plants and fungi for food, fiber, biofuel, medicinal plants and other products used to sustain and enhance human life. Agriculture was the key development in the rise of human civilization. The study of agriculture is known as agricultural science, the history of agriculture dates back thousands of years, and its development has been driven and defined by greatly different climates, cultures, and technologies. Industrial agriculture based on large-scale monoculture farming has become the dominant agricultural methodology, genetically modified organisms are an increasing component of agriculture, although they are banned in several countries. Agricultural food production and water management are increasingly becoming global issues that are fostering debate on a number of fronts, the major agricultural products can be broadly grouped into foods, fibers, fuels, and raw materials. Specific foods include cereals, vegetables, fruits, oils, meats, fibers include cotton, wool, hemp, silk and flax. Raw materials include lumber and bamboo, other useful materials are also produced by plants, such as resins, dyes, drugs, perfumes, biofuels and ornamental products such as cut flowers and nursery plants. The word agriculture is a late Middle English adaptation of Latin agricultūra, from ager, field, Agriculture usually refers to human activities, although it is also observed in certain species of ant, termite and ambrosia beetle. To practice agriculture means to use resources to produce commodities which maintain life, including food, fiber, forest products, horticultural crops. This definition includes arable farming or agronomy, and horticulture, all terms for the growing of plants, even then, it is acknowledged that there is a large amount of knowledge transfer and overlap between silviculture and agriculture. In traditional farming, the two are often combined even on small landholdings, leading to the term agroforestry, Agriculture began independently in different parts of the globe, and included a diverse range of taxa. At least 11 separate regions of the Old and New World were involved as independent centers of origin, wild grains were collected and eaten from at least 105,000 years ago. Pigs were domesticated in Mesopotamia around 15,000 years ago, rice was domesticated in China between 13,500 and 8,200 years ago, followed by mung, soy and azuki beans. Sheep were domesticated in Mesopotamia between 13,000 and 11,000 years ago. From around 11,500 years ago, the eight Neolithic founder crops, emmer and einkorn wheat, hulled barley, peas, lentils, bitter vetch, chick peas and flax were cultivated in the Levant. Cattle were domesticated from the aurochs in the areas of modern Turkey. In the Andes of South America, the potato was domesticated between 10,000 and 7,000 years ago, along with beans, coca, llamas, alpacas, sugarcane and some root vegetables were domesticated in New Guinea around 9,000 years ago. Sorghum was domesticated in the Sahel region of Africa by 7,000 years ago, cotton was domesticated in Peru by 5,600 years ago, and was independently domesticated in Eurasia at an unknown time
13.
Inca Empire
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The Inca Empire, also known as the Incan Empire and the Inka Empire, was the largest empire in pre-Columbian America, and possibly the largest empire in the world in the early 16th century. The administrative, political and military center of the empire was located in Cusco in modern-day Peru, the Inca civilization arose from the highlands of Peru sometime in the early 13th century. Its last stronghold was conquered by the Spanish in 1572, from 1438 to 1533, the Incas incorporated a large portion of western South America, centered on the Andean Mountains, using conquest and peaceful assimilation, among other methods. The Incas considered their king, the Sapa Inca, to be the son of the sun, the Inca Empire was unique in that it lacked many features associated with civilization in the Old world. In the words of one scholar, The Incas lacked the use of wheeled vehicles, the Incan economy has been described as feudal, slave, socialist. The economy functioned largely without money and without markets, instead, exchange of goods and services was based on reciprocity between individuals and among individuals, groups, and Inca rulers. Taxes consisted of an obligation of a person to the Empire. The Inca rulers reciprocated by granting access to land and goods and providing food, the Inca referred to their empire as Tawantinsuyu, the four suyu. The four suyu were, Chinchaysuyu, Antisuyu, Qullasuyu and Kuntisuyu, the name Tawantinsuyu was, therefore, a descriptive term indicating a union of provinces. The Spanish transliterated the name as Tahuatinsuyo or Tahuatinsuyu, the term Inka means ruler or lord in Quechua and was used to refer to the ruling class or the ruling family. The Incas were a small percentage of the total population of the empire, probably numbering only 15,000 to 40,000. The Spanish adopted the term as a term referring to all subjects of the empire rather than simply the ruling class. As such the name Imperio inca referred to the nation that they encountered, the Inca people were a pastoral tribe in the Cusco area around the 12th century. Incan oral history tells a story of three caves. The center cave at Tampu Tuqu was named Qhapaq Tuqu, the other caves were Maras Tuqu and Sutiq Tuqu. Four brothers and four sisters stepped out of the middle cave and they were, Ayar Manco, Ayar Cachi, Ayar Awqa and Ayar Uchu, and Mama Ocllo, Mama Raua, Mama Huaco and Mama Qura. Out of the side caves came the people who were to be the ancestors of all the Inca clans, Ayar Manco carried a magic staff made of the finest gold. Where this staff landed, the people would live and they traveled for a long time
14.
Human sacrifice
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Human sacrifice is the act of killing one or more human beings, usually as an offering to a deity, as part of a ritual. Human sacrifice has been practiced in various cultures throughout history, closely related practices found in some tribal societies are cannibalism and headhunting. By the Iron Age, with the developments in religion, human sacrifice was becoming less common throughout the Old World. In the New World, however, human sacrifice continued to be widespread to varying degrees until the European colonization of the Americas, in modern times, even the practice of animal sacrifice has virtually disappeared from all major religions, and human sacrifice has become extremely rare. Most religions condemn the practice, and modern secular laws treat it as murder, in a society which condemns human sacrifice, the term ritual murder is used. Human sacrifice is distinguished from infanticide, infanticide is deliberately causing the death of an unwanted infant or young child, but without a ritualistic or religious purpose. The idea of sacrifice has its roots in deep prehistory. From its historical occurrences it seems mostly associated with neolithic or nomadic cultures, Human sacrifice has been practiced on a number of different occasions and in many different cultures. The various rationales behind human sacrifice are the same that motivate religious sacrifice in general, Human sacrifice is intended to bring good fortune and to pacify the gods, for example in the context of the dedication of a completed building like a temple or bridge. There is a Chinese legend that there are thousands of people entombed in the Great Wall of China, for the re-consecration of the Great Pyramid of Tenochtitlan in 1487, the Aztecs reported that they killed about 80,400 prisoners over the course of four days. According to Ross Hassig, author of Aztec Warfare, between 10,000 and 80,400 persons were sacrificed in the ceremony, Human sacrifice can also have the intention of winning the gods favour in warfare. In Homeric legend, Iphigeneia was to be sacrificed by her father Agamemnon to appease Artemis so she would allow the Greeks to wage the Trojan War. According to the Bible, Jephthah vowed to devote to God the first creature to come out of his house to him if he won the battle against the Ammonites. His daughter was the first to come out and meet him, in some notions of an afterlife, the deceased will benefit from victims killed at his funeral. Mongols, Scythians, early Egyptians and various Mesoamerican chiefs could take most of their household, including servants and concubines, with them to the next world. This is sometimes called a sacrifice, as the leaders retainers would be sacrificed along with their master. Another purpose is divination from the parts of the victim. According to Strabo, Celts stabbed a victim with a sword, headhunting is the practice of taking the head of a killed adversary, for ceremonial or magical purposes, or for reasons of prestige
15.
Lava dome
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In volcanology, a lava dome or volcanic dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. The geochemistry of lava domes can vary from basalt to rhyolite although most preserved domes tend to have high silica content, the characteristic dome shape is attributed to high viscosity that prevents the lava from flowing very far. This high viscosity can be obtained in two ways, by high levels of silica in the magma, or by degassing of fluid magma. Since viscous basaltic and andesitic domes weather fast and easily break apart by further input of fluid lava, most of the domes have high silica content. Existence of lava domes has been suggested for some domed structures on the Martian surface in the part of Arcadia Planitia. Lava domes evolve unpredictably, due to non-linear dynamics caused by crystallization, domes undergo various processes such as growth, collapse, solidification and erosion. Lava domes grow by endogenic dome growth or exogenic dome growth, the former implies dome interior expansion to accommodate new lava and the latter refers to superficial piling up of lava. It is the viscosity of the lava that prevents it from flowing far from the vent from which it extrudes. Domes may reach heights of several hundred meters, and can grow slowly and steadily for months, years, the sides of these structures are composed of unstable rock debris. Due to the intermittent buildup of gas pressure, erupting domes can often experience episodes of explosive eruption over time, if part of a lava dome collapses while it is still molten, it can produce pyroclastic flows, one of the most lethal forms of volcanic event. Other hazards associated with domes are the destruction of property, forest fires. Lava domes are one of the structural features of many stratovolcanoes worldwide. Lava domes are prone to unusually dangerous explosions since they contain rhyolitic silica-rich lava, characteristics of lava dome eruptions include shallow, long-period and hybrid seismicity, which is attributed to excess fluid pressures in the contributing vent chamber. Other characteristics of lava domes include their hemispherical shape, cycles of dome growth over long periods. The average rate of growth may be used as a rough indicator of magma supply. A cryptodome is a structure created by accumulation of viscous magma at a shallow depth. Coulées are lava domes that have experienced some flow away from their original position, the worlds largest known dacite flow is the Chao dacite dome complex, a huge coulée flow-dome between two volcanoes in northern Chile. This flow is over 14 kilometres long, has obvious flow features like pressure ridges, there is another prominent coulée flow on the flank of Llullaillaco volcano, in Argentina, and other examples in the Andes
16.
Stratovolcano
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A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a profile and periodic explosive eruptions and effusive eruptions. The lava flowing from stratovolcanoes typically cools and hardens before spreading far due to high viscosity, the magma forming this lava is often felsic, having high-to-intermediate levels of silica, with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as 15 km, stratovolcanoes are sometimes called composite volcanoes because of their composite layered structure built up from sequential outpourings of eruptive materials. They are among the most common types of volcanoes, in contrast to the less common shield volcanoes, two famous stratovolcanoes are Krakatoa, best known for its catastrophic eruption in 1883 and Vesuvius, famous for its destruction of the towns Pompeii and Herculaneum in 79 CE. Both eruptions claimed thousands of lives, in modern times, Mount Saint Helens and Mount Pinatubo have erupted catastrophically. Existence of stratovolcanoes has not been proved on other bodies of the solar system with one exception. Their existence was suggested for some isolated massifs on Mars, e. g. Zephyria Tholus, stratovolcanoes are common at subduction zones, forming chains along plate tectonic boundaries where oceanic crust is drawn under continental crust or another oceanic plate. The release of water from hydrated minerals is termed dewatering, and occurs at pressures and temperatures for each mineral. The magma then rises through the crust, incorporating silica-rich crustal rock, when the magma nears the top surface, it pools in a magma chamber under or within the volcano. There, the low pressure allows water and other volatiles dissolved in the magma to escape from solution, as occurs when a bottle of carbonated water is opened. Once a critical volume of magma and gas accumulates, the obstacle of the cone is overcome. In recorded history, explosive eruptions at subduction zone volcanoes have posed the greatest hazard to civilizations. Subduction-zone stratovolcanoes, such as Mount St. Helens, Mount Etna and Mount Pinatubo, typically erupt with explosive force, as a consequence, the tremendous internal pressures of the trapped volcanic gases remain in the pasty magma. Following the breaching of the chamber, the magma degasses explosively. The gases and water out with speed and force. Since 1600 CE, nearly 300,000 people have killed by volcanic eruptions. Most deaths were caused by flows and mudflows, deadly hazards that often accompany explosive eruptions of subduction-zone stratovolcanoes
17.
Volcanic cone
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Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature, types of volcanic cones include stratocones, spatter cones, tuff cones, and cinder cones. Stratocones are large cone-shaped volcanoes made up of lava flows, explosively erupted pyroclastic rocks, unlike shield volcanoes, they are characterized by a steep profile and periodic, often alternating, explosive eruptions and effusive eruptions. Some have collapsed craters called calderas, the central core of a stratocone is commonly dominated by a central core of intrusive rocks that range from around 500 meters to over several kilometers in diameter. This central core is surrounded by generations of lava flows, many of which are brecciated. The typical stratocone is an andesitic to dacitic volcano that is associated with subduction zones and they are also known as either stratified volcano, composite cone, bedded volcano, cone of mixed type or Vesuvian-type volcano. A spatter cone is a low, steep-sided hill or mound that consists of welded lava fragments, called spatter, typically, spatter cones are about 3–5 meters high. In case of a fissure, lava fountaining will create broad embankments of spatter, called spatter ramparts. Spatter cones are circular and cone shaped, while spatter ramparts are linear wall-like features. Spatter cones and spatter ramparts are typically formed by lava fountaining associated with mafic, highly fluid lavas, as blobs of molten lava, spatter, are erupted into the air by a lava fountain, they can lack the time needed to cool completely before hitting the ground. Consequently, the spatter are not fully solid, like taffy, as they land, as a result, the spatter builds up a cone that is composed of spatter either agglutinated or welded to each other. They are characterized by rims that have a maximum relief of 100–800 meters above the crater floor. They typically have a rim to rim diameter of 300–5,000 meters, a tuff cone consists typically of thick-bedded pyroclastic flow and surge deposits created by eruption-fed density currents and bomb-scoria beds derived from fallout from its eruption column. The tuffs composing a tuff cone have commonly been altered, palagonitized, by either its interaction with groundwater or when it was deposited warm and wet. The pyroclastic deposits of tuff cones differ from the deposits of spatter cones by their lack or paucity of lava spatter, smaller grain-size. Typically, but not always, tuff cones lack associated lava flows and they are characterized by rims that have a low, broad topograhic profiles and gentle topographic slopes that are 25 degrees or less. The maximum thickness of the pyroclastic debris comprising the rim of a tuff ring is generally thin
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Cirque
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A cirque is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie and cwm, a cirque may also be a similarly shaped landform arising from fluvial erosion. The concave shape of a glacial cirque is open on the downhill side, cliff-like slopes down which ice and glaciated debris combine and converge from the three or more higher sides. The fluvial cirque or makhtesh, found in karst landscapes, is formed by intermittent river flow cutting through layers of limestone, a common feature for all fluvial-erosion cirques is a terrain which includes erosion resistant upper structures overlying materials which are more easily eroded. Glacial cirques are found amongst mountain ranges throughout the world, classic cirques are typically about one kilometer long, situated high on a mountainside near the firn line, they are typically partially surrounded on three sides by steep cliffs. The highest cliff often is called a headwall, the fourth side forms the lip, threshold or sill, the side at which the glacier flowed away from the cirque. Many glacial cirques contain tarns dammed by either till or a bedrock threshold, when enough snow accumulates it can flow out the opening of the bowl and form valley glaciers which may be several kilometers long. These areas are sheltered from heat, encouraging the accumulation of snow, if the accumulation of snow increases, the process of nivation follows, whereby a hollow in a slope may be enlarged by ice segregation weathering and glacial erosion. Ice segregation erodes the rock vertical rock face and causes it to disintegrate, eventually, this hollow may become large enough that glacial erosion intensifies. The enlarging of this open ended concavity creates a larger leeward deposition zone, debris in the ice also may abrade the bed surface, should ice move down a slope it would have a ‘sandpaper effect’ on the bedrock beneath, on which it scrapes. Eventually, the hollow may become a bowl shape in the side of the mountain, with the headwall being weathered by ice segregation. The basin will become deeper as it continues to be eroded by ice segregation and abrasion, should ice segregation, plucking and abrasion continue, the dimensions of the cirque will increase, but the proportion of the landform would remain roughly the same. A bergschrund forms when the movement of the glacier separates the moving ice from the ice forming a crevasse. The method of erosion of the headwall lying between the surface of the glacier and the floor has been attributed to freeze-thaw mechanisms. The temperature within the bergschrund changes very little, however, studies have shown that ice segregation may happen with only changes in temperature. Water that flows into the bergschrund can be cooled to freezing temperatures by the ice allowing freeze-thaw mechanisms to occur. If two adjacent cirques erode toward one another, an arête, or steep sided ridge, forms, when three or more cirques erode toward one another, a pyramidal peak is created. In some cases, this peak will be accessible by one or more arêtes
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Andean Volcanic Belt
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The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador and Peru. It formed as a result of subduction of the Nazca Plate, the belt is subdivided into four main volcanic zones that are separated from each other by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, while some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences within volcanic zones and even between neighboring volcanoes. Romeral in Colombia is the northernmost member of the Andean Volcanic Belt, South of latitude 49° S within the Austral Volcanic Zone volcanic activity decreases with the southernmost volcano Fueguino in Tierra del Fuego archipelago. The Andean Volcanic Belt is segmented into four areas of active volcanism. The Northern Volcanic Zone extends from Colombia to Ecuador and includes all volcanoes on the mainland of these countries. Of the zones volcanoes,55 are located in Ecuador while 19 are in Colombia, in Ecuador the volcanoes are located in the Cordillera Occidental and Cordillera Real while in Colombia they are located in Cordillera Central. The volcanic arc has formed due to subduction of the Nazca Plate under western South America, some volcanoes of the Northern Volcanic Zone, such as Galeras and Nevado del Ruiz that lie in densely populated highland areas, are major sources of hazards. It has been estimated that crustal thickness beneath this region varies from around 40 to perhaps more than 55 km, sangay is the southernmost volcano of the Northern Volcanic Zone. The Central Volcanic Zone is an arc in western South America. It is one of the four zones of the Andes. The Central Volcanic Zone extends from Peru to Chile and forms the boundary of the Altiplano plateau. The volcanic arc has formed due to subduction of the Nazca Plate under western South America along the Peru–Chile Trench, the CVZ is characterized by a continental crust that reaches a thickness of approximately 70 km. Within this zone there are 44 major and 18 minor volcanic centers that are considered to be active, other silicic systems are Los Frailes ignimbrite plateau in Bolivia, and the caldera complexes of Incapillo and Cerro Galán in Argentina. The South Volcanic Zone extends roughly from Central Chiles Andes at the latitude of Santiago, 33°S, to Cerro Arenales in Aysén Region at ca. 46°S, a distance of well over 870 mi, the arc has formed due to subduction of the Nazca Plate under the South American Plate along the Peru–Chile Trench. The southern end of the SVZ is marked by the Chile Triple Junction where the Chile Rise subducts under South America at the Taitao Peninsula giving origin to the Patagonian Volcanic Gap, further south lies the Austral Volcanic Zone. During the Pliocene the SVZ south of 38°S consisted of a volcanic arc
20.
Fault (geology)
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In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock-mass movement. Large faults within the Earths crust result from the action of tectonic forces. Energy release associated with movement on active faults is the cause of most earthquakes. A fault plane is the plane that represents the surface of a fault. A fault trace or fault line is the intersection of a plane with the ground surface. A fault trace is also the line commonly plotted on maps to represent a fault. Since faults do not usually consist of a single, clean fracture, the two sides of a non-vertical fault are known as the hanging wall and footwall. By definition, the wall occurs above the fault plane. This terminology comes from mining, when working a tabular ore body, because of friction and the rigidity of rocks, they cannot glide or flow past each other easily, and occasionally all movement stops. A fault in ductile rocks can also release instantaneously when the rate is too great. The energy released by instantaneous strain-release causes earthquakes, a common phenomenon along transform boundaries, slip is defined as the relative movement of geological features present on either side of a fault plane, and is a displacement vector. A faults sense of slip is defined as the motion of the rock on each side of the fault with respect to the other side. In practice, it is only possible to find the slip direction of faults. Based on direction of slip, faults can be categorized as, strike-slip. Dip-slip, offset is predominantly vertical and/or perpendicular to the fault trace, oblique-slip, combining significant strike and dip slip. The fault surface is usually vertical and the footwall moves either left or right or laterally with very little vertical motion. Strike-slip faults with left-lateral motion are known as sinistral faults. Those with right-lateral motion are known as dextral faults
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Precambrian
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The Precambrian is the earliest period of Earths history, set before the current Phanerozoic Eon. The Precambrian is a supereon that is subdivided into three eons of the time scale. It spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 541 million years ago, the Precambrian accounts for 89% of geologic time. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earths history, the Precambrian fossil record is poorer than that of the succeeding Phanerozoic, and fossils from that time are of limited biostratigraphic use. This is because many Precambrian rocks have been metamorphosed, obscuring their origins, while others have been destroyed by erosion. A stable crust was apparently in place by 4,412 Ma, the term Precambrian is recognized by the International Commission on Stratigraphy as a general term including the Archean and Proterozoic eons. It is still used by geologists and paleontologists for general discussions not requiring the more specific eon names and it was briefly called the Cryptozoic eon. A specific date for the origin of life has not been determined, carbon found in 3.8 billion year old rocks from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have found in Western Australia. Probable fossils 100 million years older have been found in the same area, there is a fairly solid record of bacterial life throughout the remainder of the Precambrian. The oldest fossil evidence from that era of such complex life comes from the Lantian formation of the Ediacarian period, a very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota, hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic era. By the middle of the following Cambrian period, a diverse fauna is recorded in the Burgess Shale. The explosion in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life, while land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Evidence of the details of plate motions and other activity in the Precambrian has been poorly preserved. It is generally believed that small proto-continents existed prior to 4280 Ma, the supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch, one of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a Snowball Earth. The atmosphere of the early Earth is not well understood, most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and was lacking in free oxygen
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Paleozoic
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The Paleozoic Era is the earliest of three geologic eras of the Phanerozoic Eon, from 541 to 252.17 million years ago. It is the longest of the Phanerozoic eras, and is subdivided into six periods, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous. The Paleozoic comes after the Neoproterozoic era of the Proterozoic and is followed by the Mesozoic, the Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earths history, known as the Cambrian explosion, fish, arthropods, amphibians, anapsids, synapsids, euryapsids and diapsids all evolved during the Paleozoic. Life began in the ocean but eventually transitioned onto land, and by the late Paleozoic, Great forests of primitive plants covered the continents, many of which formed the coal beds of Europe and eastern North America. Towards the end of the era, large, sophisticated diapsids and synapsids were dominant, the Paleozoic Era ended with the largest extinction event in the history of Earth, the Permian–Triassic extinction event. The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover, recovery of life in the sea may have been much faster. The Paleozoic era began and ended with supercontinents and in between were the rise of mountains along the margins, and flooding and draining of shallow seas between. At its start, the supercontinent Pannotia broke up, paleoclimatic studies and evidence of glaciers indicate that central Africa was most likely in the polar regions during the early Paleozoic. During the early Paleozoic, the huge continent Gondwana formed or was forming, by mid-Paleozoic, the collision of North America and Europe produced the Acadian-Caledonian uplifts, and a subduction plate uplifted eastern Australia. There are six periods in the Paleozoic Era, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, the Cambrian spans from 541 million years to 485 million years and is the first period of the Paleozoic era of the Phanerozoic. The Cambrian marked a boom in evolution in an event known as the Cambrian explosion in which the largest number of creatures evolved in any period of the history of the Earth. Creatures like algae evolved, but the most ubiquitous of that period were the armored arthropods, almost all marine phyla evolved in this period. During this time, the supercontinent Pannotia begins to break up, the Ordovician spanned from 485 million years to 443 million years ago. The Ordovician is a time in Earths history in many of the biological classes still prevalent today evolved, such as primitive fish, cephalopods. The most common forms of life, however, were trilobites, snails, more importantly, the first arthropods went ashore to colonize the empty continent of Gondwana. By the end of the Ordovican, Gondwana was at the pole, early North America had collided with Europe. Glaciation of Africa resulted in a drop in sea level
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Mesozoic
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The Mesozoic Era is an interval of geological time from about 252 to 66 million years ago. This Era is also called from a paleobotanist view the Age of Conifers, Mesozoic means middle life, deriving from the Greek prefix meso-/μεσο- for between and zōon/ζῷον meaning animal or living being. It is one of three eras of the Phanerozoic Eon, preceded by the Paleozoic and succeeded by the Cenozoic. The era is subdivided into three periods, the Triassic, Jurassic, and Cretaceous, which are further subdivided into a number of epochs. The Mesozoic was a time of significant tectonic, climate and evolutionary activity, the era witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses that would eventually move into their current positions. The climate of the Mesozoic was varied, alternating between warming and cooling periods, overall, however, the Earth was hotter than it is today. Birds first appeared in the Jurassic, having evolved from a branch of theropod dinosaurs, the first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg —until the Cenozoic. Following the Paleozoic, the Mesozoic extended roughly 186 million years and this time frame is separated into three geologic periods. It is also known as the Great Dying because it is considered the largest mass extinction in the Earths history, the upper boundary of the Mesozoic is set at the Cretaceous–Paleogene extinction event, which may have been caused by the impactor that created Chicxulub Crater on the Yucatán Peninsula. Towards the Late Cretaceous large volcanic eruptions are believed to have contributed to the Cretaceous–Paleogene extinction event. Approximately 50% of all genera became extinct, including all of the non-avian dinosaurs, the Triassic ranges roughly from 252 million to 201 million years ago. The Triassic is a time in Earths history bracketed between the Permian Extinction and the Triassic–Jurassic extinction event, two of the big five, and precedes the Jurassic Period and it has three major epochs, the Early Triassic, the Middle Triassic and the Late Triassic. The Early Triassic was between about 252 million to 247 million years ago and was dominated by deserts as Pangaea had not yet broken up, thus the interior was nothing, the Earth had just witnessed a massive die-off in which 95% of all life became extinct. The most common life on earth were Lystrosaurus, labyrinthodonts. Temnospondyls evolved during this time and would be the dominant predator for much of the Triassic, the Middle Triassic spans roughly from 247 million to 237 million years ago. The Middle Triassic featured the beginnings of the breakup of Pangaea, the ecosystem had recovered from the devastation that was the Great Dying. Algae, sponge, corals, and crustaceans all had recovered, new aquatic reptiles evolved, such as ichthyosaurs and nothosaurs. Meanwhile, on land, pine forests flourished, as did groups of insects like mosquitoes, the first ancient crocodilians evolved, which sparked competition with the large amphibians that had since ruled the freshwater world
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Cenozoic
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The Cenozoic Era is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and covering the period from 66 million years ago to the present day. The Cenozoic is also known as the Age of Mammals, because of the mammals that dominated, such as Entelodont, Paraceratherium. The extinction of many large groups such as non-avian dinosaurs, Plesiosauria and Pterosauria allowed the mammals and birds to greatly diversify. Early in the Cenozoic, following the K-Pg event, the planet was dominated by relatively small fauna, including mammals, birds, reptiles. From a geological perspective, it did not take long for mammals, some flightless birds grew larger than humans. These species are referred to as terror birds, and were formidable predators. Mammals came to occupy almost every available niche, and some also grew very large, the Earths climate had begun a drying and cooling trend, culminating in the glaciations of the Pleistocene Epoch, and partially offset by the Paleocene-Eocene Thermal Maximum. The continents also began looking roughly familiar at this time and moved into their current positions. The Cenozoic is divided into three periods, the Paleogene, Neogene, and Quaternary, and seven epochs, the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene. The common use of epochs during the Cenozoic helps paleontologists better organize, there is also more detailed knowledge of this era than any other because of the relatively young, well-preserved rocks associated with it. The Paleogene spans from the extinction of dinosaurs,66 million years ago. It features three epochs, the Paleocene, Eocene and Oligocene, the Paleocene ranged from 66 million to 56 million years ago. The Paleocene is a point between the devastation that is the K-T extinction, to the rich jungles environment that is the Early Eocene. The Early Paleocene saw the recovery of the earth, the continents began to take their modern shape, but all the continents and subcontinent India were separated from each other. Afro-Eurasia was separated by the Tethys Sea, and the Americas were separated by the strait of Panama and this epoch featured a general warming trend, with jungles eventually reaching the poles. The oceans were dominated by sharks as the large reptiles that had once ruled became extinct, archaic mammals filled the world such as creodonts and early primates that evolved during the Mesozoic, and as a result, there was nothing over 10 kilograms. The Eocene Epoch ranged from 56 million years to 33.9 million years ago, in the Early-Eocene, life was small and lived in cramped jungles, much like the Paleocene. There was nothing over the weight of 10 kilograms, among them were early primates, whales and horses along with many other early forms of mammals
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Andesite
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For the extinct cephalopod genus, see Andesites. Andesite is an igneous, volcanic rock, of intermediate composition. In a general sense, it is the type between basalt and dacite, and ranges from 57 to 63% silicon dioxide as illustrated in TAS diagrams. The mineral assemblage is dominated by plagioclase plus pyroxene or hornblende. Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals, alkali feldspar may be present in minor amounts. The quartz-feldspar abundances in andesite and other rocks are illustrated in QAPF diagrams. Classification of andesites may be refined according to the most abundant phenocryst, example, hornblende-phyric andesite, if hornblende is the principal accessory mineral. Andesite can be considered as the equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs, the average composition of the continental crust is andesitic. Along with basalts they are a component of the Martian crust. The name andesite is derived from the Andes mountain range, magmatism in island arc regions comes from the interplay of the subducting plate and the mantle wedge, the wedge-shaped region between the subducting and overriding plates. During subduction, the oceanic crust is submitted to increasing pressure and temperature. Hydrous minerals such as amphibole, zeolites, chlorite etc. dehydrate as they change to more stable, anhydrous forms, releasing water, fluxing water into the wedge lowers the solidus of the mantle material and causes partial melting. Due to the density of the partially molten material, it rises through the wedge until it reaches the lower boundary of the overriding plate. Basalt thus formed can contribute to the formation of andesite through fractional crystallization, partial melting of crust, or magma mixing, andesite is typically formed at convergent plate margins but may occur in other tectonic settings. Intermediate volcanic rocks are created via several processes, Fractional crystallization of a mafic parent magma and this removal can take place in a variety of ways, but most commonly this occurs by crystal settling. The first minerals to crystallize and be removed from a parent are olivines and amphiboles. These mafic minerals settle out of the magma, forming mafic cumulates, there is geophysical evidence from several arcs that large layers of mafic cumulates lie at the base of the crust
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Dacite
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Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite, the word dacite comes from Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described. Dacite consists mostly of feldspar with biotite, hornblende. It has quartz as rounded, corroded phenocrysts, or as an element of the ground-mass, the relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram. The TAS classification, based on silica and alkali contents, puts dacite in the O3 sector, the plagioclase ranges from oligoclase to andesine and labradorite. Sanidine occurs, although in small proportions, in some dacites, the groundmass of these rocks is composed of plagioclase and quartz. In the hand specimen many of the hornblende and biotite dacites are grey or pale brown and yellow rocks with white feldspars, other dacites, especially pyroxene bearing dacites, are darker colored. In thin section, dacites may have an aphanitic to porphyritic texture, porphyritic dacites contain blocky highly zoned plagioclase phenocrysts and/or rounded corroded quartz phenocrysts. Subhedral hornblende and elongated biotite grains are present, sanidine phenocrysts and augite are found in some samples. Dacite usually forms as a rock such as a dike or sill. Examples of this type of dacite outcrop are found in northwestern Montana, nevertheless, because of the moderate silica content, dacitic magma is quite viscous and therefore prone to explosive eruption. A notorious example of this is Mount St. Helens in which dacite domes formed from previous eruptions, pyroclastic flows may also be of dacitic composition as is the case with the Fish Canyon Tuff of La Garita Caldera. Dacitic magma is formed by the subduction of oceanic crust under a thick felsic continental plate. Oceanic crust is hydrothermally altered causing addition of quartz and sodium, as the young, hot oceanic plate is subducted under continental crust, the subducted slab partially melts and interacts with the upper mantle through convection and dehydration reactions. The process of subduction creates metamorphism in the subducting slab, when this slab reaches the mantle and initiates the dehydration reactions, minerals such as talc, serpentine, mica and amphiboles break down generating a more sodic melt. The magma then continues to migrate upwards causing differentiation and becomes even more sodic and silicic as it rises, once at the cold surface, the sodium rich magma crystallizes plagioclase, quartz and hornblende. Accessory minerals like pyroxenes provide insight to the history of the magma, the formation of dacite provides a great deal of information about the connection between oceanic crust and continental crust. It provides a model for the generation of felsic, buoyant, perennial rock from a mafic, dense, the process by which dacite forms has been used to explain the generation of continental crust during the Archean eon
27.
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
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Phenocryst
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A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a difference in the size of the crystals are called porphyries. Phenocrysts often have euhedral forms, either due to growth within a magma. Normally the term phenocryst is not used unless the crystals are directly observable, phenocrysts below this level, but still larger than the groundmass crystals, are termed microphenocrysts. Very large phenocrysts are termed megaphenocrysts, some rocks contain both microphenocrysts and megaphenocrysts. In metamorphic rocks, crystals similar to phenocrysts are called porphyroblasts, phenocrysts are more often found in the lighter igneous rocks such as felsites and andesites, although they occur throughout the igneous spectrum including in the ultramafics. The largest crystals found in some pegmatites are often phenocrysts being significantly larger than the other minerals, rocks can be classified according to the nature, size and abundance of phenocrysts, and the presence or absence of phenocrysts is often noted when a rock name is determined. Porphyritic rocks are named using mineral name modifiers, normally in decreasing order of abundance. Thus when olivine forms the primary phenocrysts in a basalt, the name may be refined from basalt to porphyritic olivine basalt or olivine phyric basalt. Similarly, a basalt with olivine as the dominate phenocrysts, but with lesser amounts of plagioclase phenocrysts, categorizing a rock as aphyric or as sparsely phyric is often a question of whether a significant number of crystals exceed the minimum size. Geologists use phenocrysts to help determine rock origins and transformations, as when and whether crystals form depends on pressure, fumiko Shido first applied this technique to oceanic basalts, further development came from Tsugio Shibata, and from W. B. Plagioclase phenocrysts often exhibit zoning with a more calcic core surrounded by progressively more sodic rinds and this zoning reflects the change in magma composition as crystallization progresses. In rapakivi granites, phenocrysts of orthoclase are enveloped within rinds of sodic plagioclase such as oligoclase, in shallow intrusives or volcanic flows phenocrysts which formed before eruption or shallow emplacement are surrounded by a fine-grained to glassy matrix. These volcanic phenocrysts often show flow banding, an arrangement of lath-shaped crystals. These characteristics provide clues to the rocks origins, similarly, intragranular microfractures and any intergrowth among crystals provide additional clues. Williams, Howel, Turner, Francis J. & Gilbert, Charlse M. Petrography, proceedings of the Ocean Drilling Program, Vol.187 Initial Reports
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Hornblende
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Hornblende is a complex inosilicate series of minerals. It is not a mineral in its own right, but the name is used as a general or field term. Hornblende is a mixture of three molecules, a calcium-iron-magnesium silicate, an aluminium-iron-magnesium silicate, and an iron-magnesium silicate. The general formula can be given as 2–358O222, some metals vary in their occurrence and magnitude, Manganese and titanium are often present. Sodium and potassium are present and fluorine often substitutes for the hydroxyl in the crystalline structure. Hornblende has a hardness of 5–6, a gravity of 2. 9–3.4 and is typically an opaque green. Its cleavage angles are at 56 and 124 degrees and it is most often confused with various pyroxene minerals and biotite mica, which are black and can be found in granite and in charnockite. Hornblende is a constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro, basalt, andesite, gneiss. It is the mineral of amphibolites. Very dark brown to black hornblendes that contain titanium are ordinarily called basaltic hornblende, from the fact that they are usually a constituent of basalt, hornblende alters easily to chlorite and epidote. A rare variety of hornblende contains less than 5% of iron oxide, is gray to white in color, and named edenite, from its locality in Edenville, Orange County, New York. List of minerals Hurlbut, Cornelius S. Klein, Cornelis,1985, Manual of Mineralogy, 20th ed. John Wiley and Sons, New York, p 416-7, ISBN 0-471-80580-7 Scandinavian mineral gallery retrieved 06/21/05
30.
Plagioclase
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Plagioclase is a series of tectosilicate minerals within the feldspar group. Rather than referring to a mineral with a specific chemical composition, plagioclase is a continuous solid solution series. This was first shown by the German mineralogist Johann Friedrich Christian Hessel in 1826, the series ranges from albite to anorthite endmembers, where sodium and calcium atoms can substitute for each other in the minerals crystal lattice structure. Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or record-groove effect, plagioclase is a major constituent mineral in the Earths crust, and is consequently an important diagnostic tool in petrology for identifying the composition, origin and evolution of igneous rocks. Plagioclase is also a constituent of rock in the highlands of the Earths moon. Analysis of thermal emission spectra from the surface of Mars suggests that plagioclase is the most abundant mineral in the crust of Mars, the extinction angle is an optical characteristic and varies with the albite fraction. There are several named plagioclase feldspars that fall between albite and anorthite in the series, the following table shows their compositions in terms of constituent anorthite and albite percentages. Anorthite was named by Gustav Rose in 1823 from the Ancient Greek meaning oblique, anorthite is a comparatively rare mineral but occurs in the basic plutonic rocks of some orogenic calc-alkaline suites. Albite is named from the Latin albus, in reference to its pure white color. It is a common and important rock-making mineral associated with the more acid rock types and in pegmatite dikes, often with rarer minerals like tourmaline. The intermediate members of the group are very similar to each other. Bytownite, named after the name for Ottawa, Canada, is a rare mineral occasionally found in more basic rocks. Labradorite is the characteristic feldspar of the basic rock types such as diorite, gabbro, andesite. Labradorite frequently shows an iridescent display of colors due to light refracting within the lamellae of the crystal and it is named after Labrador, where it is a constituent of the intrusive igneous rock anorthosite which is composed almost entirely of plagioclase. A variety of known as spectrolite is found in Finland. Andesine is a mineral of rocks such as diorite which contain a moderate amount of silica. Oligoclase is common in granite, syenite, diorite, and gneiss and it is a frequent associate of orthoclase. The name oligoclase is derived from the Greek for little and fracture, sunstone is mainly oligoclase with flakes of hematite
31.
Altitudinal zonation
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Altitudinal zonation in mountainous regions describes the natural layering of ecosystems that occurs at distinct altitudes due to varying environmental conditions. Temperature, humidity, soil composition, and solar radiation are important factors in determining altitudinal zones, Altitudinal zonation was first hypothesized by geographer Alexander von Humboldt who noticed that temperature drops with increasing elevation. Zonation also occurs in intertidal and marine environments, as well as on shorelines, scientist C. Hart Merriam observed that changes in vegetation and animals in altitudinal zones map onto changes expected with increased latitude in his concept of life zones. Today, altitudinal zonation represents a concept in mountain research. The cause of zonation is complex, due to possible interactions. Careful measurements and statistical tests are required prove the existence of discrete communities along an elevation gradient, decreasing air temperature usually coincides with increasing elevation, which directly influences the length the growing season at different altitudes of the mountain. For mountains located in deserts, extreme temperatures also limit the ability of large deciduous or coniferous trees to grow near the base of mountains. In addition, plants can be sensitive to soil temperatures. The most important variable is precipitation at various altitudes, as warm, moist air rises up the windward side of a mountain, the air temperature cools and loses its capacity to hold moisture. Thus, the greatest amount of rainfall is expected at mid-altitudes, above a certain elevation the rising air becomes too dry and cold, and thus discourages tree growth. Although rainfall may not be a significant factors for some mountains, both overall levels of precipitation and humidity influence soil moisture as well. One of the most important factors that controls the lower boundary of the encinal or forest level is the ratio of evaporation to soil moisture, the nutrient content of soils at different altitudes further complicates the demarcation of altitudinal zones. Soils with higher nutrient content, due to higher decomposition rates or greater weathering of rocks, better support larger trees, the altitude of better soils varies with the particular mountain being studied. For example, for mountains found in the rain forest regions. At this latitude more acidic, humose soils exist at elevations in the montane or subapline levels. In a different example, weathering is hampered by low temperatures at higher elevations in the Rocky Mountain of the western United States, in addition to physical forces, biological forces may also produce zonation. For example, a competitor can force weaker competitors to higher or lower positions on the elevation gradient. The importance of competition is difficult to assess without experiments, which are expensive, however, there is an accumulating body of evidence that competitively dominant plants may seize the preferred locations
32.
Quinoa
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Quinoa is the common name for Chenopodium quinoa of the flowering plant family Amaranthaceae. It is grown as a crop primarily for its edible seeds. It is a rather than a true cereal, due to it not being a grass. Quinoa is closely related to the edible plants beetroot, spinach, after harvest, the seeds are processed to remove the outer coating containing the bitter-tasting saponins. Generally, the seeds are cooked the same way as rice, the leaves are sometimes eaten as a leaf vegetable, much like amaranth, but commercial availability of quinoa greens is limited. When cooked, the nutrient composition is comparable to common cereals like wheat and rice, supplying a moderate amount of dietary fiber, the Food and Agriculture Organization of the United Nations declared 2013 to be the International Year of Quinoa. Chenopodium quinoa is an annual plant, usually about 1–2 m high. It has broad, generally powdery, hairy, lobed leaves, the woody central stem is branched or unbranched depending on the variety and may be green, red or purple. The flowering panicles arise from the top of the plant or from leaf axils along the stem, each panicle has a central axis from which a secondary axis emerges either with flowers or bearing a tertiary axis carrying the flowers. The green hypogynous flowers have a simple perianth and are generally self-fertilizing, the fruits are about 2 mm in diameter and of various colors—from white to red or black, depending on the cultivar. Chenopodium quinoa is believed to have been domesticated in the Peruvian Andes from wild or weed populations of the same species. There are non-cultivated quinoa plants that grow in the area it is cultivated, in their natural state, the seeds have a coating which contains bitter-tasting saponins, making them unpalatable. Most of the grain sold commercially has been processed to remove this coating and this bitterness has beneficial effects during cultivation, as it deters birds and therefore the plant requires minimal protection. The genetic control of bitterness involves quantitative inheritance, the toxicity category rating of the saponins in quinoa treats them as mild eye and respiratory irritants and as a low gastrointestinal irritant. In South America, the saponins have many uses, including their use as a detergent for clothing and washing, additionally, high levels of oxalic acid are in the leaves and stems of all species of the Chenopodium genus, and in the related genera of the Amaranthaceae family. The risks associated with quinoa are minimal, provided it is properly prepared, raw, uncooked quinoa is 13% water, 64% carbohydrates, 14% protein and 6% fat. Nutritional evaluations indicate that a 100 g serving of raw quinoa is a source of protein, dietary fiber, several B vitamins. After cooking, which is the preparation for eating, quinoa is 72% water, 21% carbohydrates, 4% protein and 2% fat
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Alfalfa
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Alfalfa /ælˈfælfə/, Medicago sativa also called lucerne, is a perennial flowering plant in the pea family Fabaceae cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as well as a green manure, the name alfalfa is used in North America. The name lucerne is the commonly used name in the United Kingdom, South Africa, Australia. The plant superficially resembles clover, especially young, when trifoliate leaves comprising round leaflets predominate. Later in maturity, leaflets are elongated and it has clusters of small purple flowers followed by fruits spiralled in 2 to 3 turns containing 10–20 seeds. Alfalfa is native to temperate climates. It has been cultivated as livestock fodder since at least the era of the ancient Greeks, Alfalfa sprouts are a common ingredient in dishes made in South Indian cuisine. Alfalfa seems to have originated in south-central Asia, and was first cultivated in ancient Iran, according to Pliny, it was introduced to Greece in about 490 BC when the Persians invaded Greek territory. Alfalfa cultivation is discussed in the fourth-century AD book Opus Agriculturae by Palladius, stating, the crop may be cut four or six times a year. A jugerum of it is sufficient for three horses all the year. It may be given to cattle, but new provender is at first to be administered very sparingly, Pliny and Palladius called alfalfa in Latin medica, a name that referred to the Medes, a people who lived in ancient Iran. The ancient Greeks and Romans believed, probably correctly, that came from the Medes land. This name is the root of the scientific name for the alfalfa genus. In ancient India, Ayurvedic texts prescribe the use of Alfalfa seeds and sprouts for improving blood cell production and its leaves and stem as a source of protein. The medieval Arabic agricultural writer Ibn al-Awwam, who lived in Spain in the later 12th century, discussed how to cultivate alfalfa, a 13th-century general-purpose Arabic dictionary, Lisān al-Arab, says that alfalfa is cultivated as an animal feed and consumed in both fresh and dried forms. It is from the Arabic that the Spanish name alfalfa was derived, in the 16th century, Spanish colonizers introduced alfalfa to the Americas as fodder for their horses. They were aware that alfalfa is better than grass as food for working horses, in the North American colonies of the eastern US in the 18th century, it was called lucerne, and many trials at growing it were made, but generally without sufficiently successful results. Relatively little is grown in the southeastern United States today, lucerne is the name for alfalfa in Britain, Australia, France, Germany, and a number of other countries
34.
Maize
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Maize, also known as corn, is a large grain plant first domesticated by indigenous peoples in Mexico about 10,000 years ago. The six major types of corn are dent corn, flint corn, pod corn, popcorn, flour corn, the leafy stalk of the plant produces separate pollen and ovuliferous inflorescences or ears, which are fruits, yielding kernels or seeds. Maize kernels are used in cooking as a starch. Most historians believe maize was domesticated in the Tehuacan Valley of Mexico, recent research modified this view somewhat, scholars now indicate the adjacent Balsas River Valley of south-central Mexico as the center of domestication. The Olmec and Mayans cultivated maize in numerous varieties throughout Mesoamerica, cooked and its believed that beginning about 2500 BC, the crop spread through much of the Americas. The region developed a network based on surplus and varieties of maize crops. Nevertheless, recent data indicates that the spread of maize took place even earlier, according to Piperno, A large corpus of data indicates that it was dispersed into lower Central America by 7600 BP and had moved into the inter-Andean valleys of Colombia between 7000 and 6000 BP. Since then, even earlier dates have been published, the study also demonstrated that the oldest surviving maize types are those of the Mexican highlands. Later, maize spread from this region over the Americas along two major paths and this is consistent with a model based on the archaeological record suggesting that maize diversified in the highlands of Mexico before spreading to the lowlands. Before they were domesticated, maize plants only grew small,25 millimetres long corn cobs, Maize is the most widely grown grain crop throughout the Americas, with 361 million metric tons grown in the United States in 2014. Approximately 40% of the crop—130 million tons—is used for corn ethanol, genetically modified maize made up 85% of the maize planted in the United States in 2009. After the arrival of Europeans in 1492, Spanish settlers consumed maize and explorers and traders carried it back to Europe, Spanish settlers far preferred wheat bread to maize, cassava, or potatoes. Maize flour could not be substituted for wheat for bread, since in Christian belief only wheat could undergo transubstantiation. At another level, Spaniards worried that by eating indigenous foods, which they did not consider nutritious, that not only would they weaken, despite these worries, Spaniards did consume maize and archeological evidence from Florida sites indicate they cultivated it as well. Maize spread to the rest of the world because of its ability to grow in diverse climates and it was cultivated in Spain just a few decades after Columbuss voyages and then spread to Italy, West Africa and elsewhere. The word maize derives from the Spanish form of the indigenous Taíno word for the plant and it is known by other names around the world. The word corn outside North America, Australia, and New Zealand refers to any cereal crop, in the United States, Canada, Australia, and New Zealand, corn primarily means maize, this usage started as a shortening of Indian corn. Indian corn primarily means maize, but can more specifically to multicolored flint corn used for decoration
35.
Explosive eruption
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An explosive eruption is a volcanic term to describe a violent, explosive type of eruption. Mount St. Helens in 1980 was an example, such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such that expelled lava violently froths into volcanic ash when pressure is suddenly lowered at the vent. Sometimes a lava plug will block the conduit to the summit, Explosive eruptions can send rocks, dust, gas and pyroclastic material up to 20 km into the atmosphere at rate of up to 100,000 tonnes per second, traveling at several hundred meters per second. This cloud will collapse, creating a pyroclastic flow of hot volcanic matter. An explosive eruption always begins with some form of blockage in the crater of a volcano that prevents the release of trapped in highly viscous andesitic or rhyolitic magma. The high viscosity of these forms of magma prevents the release of trapped gases, when this type of magma flows towards the surface pressure builds, eventually causing the blockage to be blasted out in an explosive eruption. The pressure from the magma and gases are released through the weakest point in the cone, however, in the case of the eruption of Mount St. Helens, pressure was released through the side of the volcano, rather than the crater. The size and duration of the column depends on the volume of magma being released, the eruption column of ash is supported by pressure from the gases being released, and as the gases are depleted, pressure falls and the eruption column begins to collapse. When the column collapses in on itself, ash and rock fall back down to the ground and these flows can travel at up to 80 km per hour, and reach temperatures of 200° to 700° Celsius. The high temperatures can cause combustion of any flammable materials in its path, including wood, vegetation, when snow and ice melt as a part of an eruption, large amounts of water mixed in with the flow can create lahars. The risk of lahars is particularly high on volcanoes such as Mount Rainier near Seattle and Tacoma, the eruption of supervolcanoes is the rarest of volcanic eruptions but also the most destructive. The timescale between these eruptions is generally marked by hundreds or thousands of years and this type of eruption generally causes destruction on a continental scale, and can also result in the lowering of temperatures worldwide. Effusive eruption Volcanic explosivity index Recent Developments in Explosive Volcanism
36.
Pyroclastic rock
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Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, pyroclastic rocks may be a range of clast sizes, from the largest agglomerates, to very fine ashes and tuffs. Pyroclasts of different sizes are classified as bombs, lapilli. Ash is considered to be pyroclastic because it is a fine dust made up of volcanic rock, one of the most spectacular forms of pyroclastic deposit are the ignimbrites, deposits formed by the high-temperature gas-and-ash mix of a pyroclastic flow event. Three modes of transport can be distinguished, pyroclastic flow, pyroclastic surge, during Plinian eruptions, pumice and ash are formed when silicic magma is fragmented in the volcanic conduit, because of decompression and the growth of bubbles. Pyroclasts are then entrained in a buoyant eruption plume which can rise several kilometers into the air, particles falling from the eruption clouds form layers on the ground. Pyroclastic density currents, which are referred to as flows or surges depending on particle concentration, the deposits of pumice-rich pyroclastic flows can be called ignimbrites. A pyroclastic eruption entails spitting or fountaining lava, where the lava will be thrown into the air along with ash, pyroclastic materials, hawaiian eruptions such as those at Kīlauea can eject clots of magma suspended into gas, this is called a fire fountain. The magma clots, if hot enough may coalesce upon landing to form a lava flow, pyroclastic deposits consist of pyroclasts which are not cemented together. Pyroclastic rocks are pyroclastic deposits which have been lithified
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Lava
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Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is called lava. The molten rock is formed in the interior of planets, including Earth. The source of the heat melts the rock within the earth is geothermal energy. When first erupted from a vent, lava is a liquid usually at temperatures from 700 to 1,200 °C. A lava flow is an outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock, the term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic, explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word lava comes from Italian, and is derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma was apparently in an account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4,1737. Serao described a flow of lava as an analogy to the flow of water. The composition of almost all lava of the Earths crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas, igneous rocks, which form lava flows when erupted, can be classified into three chemical types, felsic, intermediate, and mafic. These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the temperature, its viscosity. Felsic or silicic lavas such as rhyolite and dacite typically form lava spines, most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. Felsic magmas can erupt at temperatures as low as 650 to 750 °C, unusually hot rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States. Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium, intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Poorer in aluminium and silica than felsic lavas, and also commonly hotter, greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C
38.
Volcano
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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 also 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, therefore, 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
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Lahar
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A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley, lahars are extremely destructive, they can flow tens of metres per second, be 140 metres deep, and destroy any structures in their path. Notable lahars include those at Mount Pinatubo and Nevado del Ruiz, the word lahar is the Javanese term for flowing lava. A lahar is a volcanic mudflow or debris flow, lahars have the consistency, viscosity and approximate density of wet concrete, fluid when moving, solid at rest. Lahars can be huge.3 cubic kilometres, a lahar of sufficient size and intensity can erase virtually any structure in its path, and is capable of carving its own pathway, making the prediction of its course difficult. Conversely, a lahar quickly loses force when it leaves the channel of its flow, even frail huts may remain standing, a lahars viscosity decreases with time, and can be further thinned by rain, but it nevertheless solidifies quickly when coming to a stop. Lahars vary in size and speed, small lahars less than a few metres wide and several centimetres deep may flow a few metres per second. Large lahars hundreds of metres wide and tens of metres deep can flow tens of metres per second. With the potential to flow at speeds up to 100 kilometres per hour, and flow distances of more than 300 kilometres, a lahar can cause catastrophic destruction in its path. Lahars from the 1985 Nevado del Ruiz eruption in Colombia caused the Armero tragedy, which killed an estimated 23,000 people, a lahar caused New Zealands Tangiwai disaster, where 151 people died after a Christmas Eve express train fell into the Whangaehu River in 1953. Lahars have been responsible for 17% of volcano-related deaths between 1783 and 1997, a lahar can cause fatalities years after its precipitating eruption. For example, the Cabalantian tragedy occurred four years subsequent to the 1991 eruption of Mount Pinatubo, the word lahar is of Indonesian origin. Lahars have several causes, Snow and glaciers can be melted by lava or pyroclastic flows during an eruption. Lava flows out of vents and can mix with wet soil and mud on the slope of the volcano making a very viscous. A flood caused by a glacier, lake breakout, or heavy rainfall can release a lahar, also called glacier run or jökulhlaup Water from a crater lake, heavy rainfall on unconsolidated pyroclastic deposits. Snow and glaciers can melt during periods of mild weather Earthquakes underneath or close to the volcano can shake material loose and cause it to collapse triggering a lahar avalanche. Rainfall can cause the still-hanging slabs of solidified mud to come rushing down the slopes at a speed of more than 30 kilometres per hour, causing devastating results. Several towns in the Puyallup River valley in Washington state, including Orting, are built on top of lahar deposits that are only about 500 years old
40.
Plinian eruption
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Plinian eruptions, also known as Vesuvian eruptions, are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in 79 AD. The eruption was described in a written by Pliny the Younger, it killed his uncle. Plinian eruptions are marked by columns of gas and volcanic ash extending high into the stratosphere, the key characteristics are ejection of large amount of pumice and very powerful continuous gas blast eruptions. According to the Volcanic Explosivity Index, Plinian eruptions have a VEI of 4,5 or 6, short eruptions can end in less than a day, but longer events can take several days to months. The longer eruptions begin with production of clouds of volcanic ash, the amount of magma erupted can be so large that it depletes the magma chamber below, causing the top of the volcano to collapse, resulting in a caldera. Fine ash can deposit over large areas, Plinian eruptions are often accompanied by loud noises, such as those generated by Krakatoa. The lava is usually rhyolitic and rich in silicates, basaltic lavas are unusual for Plinian eruptions, the most recent basaltic example is the 1886 eruption of Mount Tarawera on New Zealands North Island. Pliny the Younger provided an account of his death, and suggested that he collapsed and died through inhaling poisonous gases emitted from the volcano. His body was interred under the ashes of the Vesuvius with no apparent injuries on 26 August, after the plume had dispersed. The June 2009 eruption of Sarychev Peak in Russia, the 1991 Mount Pinatubo eruption in Zambales of Central Luzon, Philippines. The 1980 eruption of Mount St. Helens in Washington, United States, the 1912 eruption of Novarupta in Alaska, United States. The 1886 eruption of Mount Tarawera in New Zealand, the 1883 eruption of Krakatoa in Sunda Strait, Indonesia. The 1815 eruption of Mount Tambora in the island of Sumbawa, the 1783 eruptions of Lakagígar in Iceland. The 1667 and 1739 eruptions of Mount Tarumae in Hokkaido, Japan, the A. D.180 Lake Taupo eruption in New Zealand. The A. D.79 eruption of Mount Vesuvius in Campania and it was the prototypical Plinian eruption. The 400s BC eruption of the Bridge River Vent in British Columbia, the 1645 BC eruption of Santorini in the south Aegean Sea, Greece. The 4860 BC eruption forming Crater Lake in Oregon, United States, the Long Valley Caldera eruption in Eastern California of United States, which happened over 760,000 years ago. According to the Volcanic Explosivity Index, a VEI of 6 to 8 is classified as Ultra Plinian, Eruptions of this type are defined by ash plumes over 25 km high and a volume of erupted material 10 km3 to 1,000 km3 in size
41.
Hot spring
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A hot spring is a spring produced by the emergence of geothermally heated groundwater that rises from the Earths crust. There are geothermal hot springs in many locations all over the crust of the earth, while some of these springs contain water that is a safe temperature for bathing, others are so hot that immersion can result in injury or death. The water temperature of a hot spring is usually 6.5 °C or more above mean air temperature, note that by this definition, thermal spring is not synonymous with the term hot spring a spring whose hot water is brought to the surface. The water temperature of the spring is usually 8.3 °C or more above the air temperature. A spring with water above the human body temperature –36.7 °C. suggest that the phrase warm spring is not useful. In general, the temperature of rocks within the earth increases with depth, the rate of temperature increase with depth is known as the geothermal gradient. If water percolates deeply enough into the crust, it will be heated as it comes into contact with hot rocks, the water from hot springs in non-volcanic areas is heated in this manner. In active volcanic zones such as Yellowstone National Park, water may be heated by coming into contact with magma, the high temperature gradient near magma may cause water to be heated enough that it boils or becomes superheated. If the water becomes so hot that it builds steam pressure and erupts in a jet above the surface of the Earth, if the water only reaches the surface in the form of steam, it is called a fumarole. If the water is mixed with mud and clay, it is called a mud pot, note that hot springs in volcanic areas are often at or near the boiling point. People have been seriously scalded and even killed by accidentally or intentionally entering these springs, Warm springs are sometimes the result of hot and cold springs mixing. They may occur within an area or outside of one. One example of a warm spring is Warm Springs, Georgia. Hot springs range in flow rate from the tiniest seeps to veritable rivers of hot water, sometimes there is enough pressure that the water shoots upward in a geyser, or fountain. There are many claims in the literature about the rates of hot springs. It should be noted there are many more high flow non-thermal springs than geothermal springs. For example, there are 33 recognized magnitude one springs (having a flow in excess of 2,800 L/s in Florida alone, silver Springs, Florida has a flow of more than 21,000 L/s. Springs with high flow rates include, The Excelsior Geyser Crater in Yellowstone National Park yields about 4,000 U. S. gal/min
42.
Magma chamber
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A magma chamber is a large underground pool of liquid rock found beneath the surface of the Earth. The molten rock in such a chamber is under pressure, and given enough time. If it finds a way to the surface, then the result will be a volcanic eruption, magma chambers are hard to detect, and most of the known ones are therefore close to the surface of the Earth, commonly between 1 km and 10 km under the surface. In geological terms, this is close to the surface, although in human terms. Magma rises through cracks from beneath and across the crust because it is less dense than the surrounding rock, when the magma cannot find a path upwards it pools into a magma chamber. Magma chambers are built up incrementally, by successive horizontal or vertical magma injections. Influx of new magma causes reaction of pre-existing crystals and the pressure in the chamber to increase, upon cooling, new mineral phases saturate and the rock type changes, typically forming gabbro, diorite, tonalite and granite or gabbro, diorite, syenite and granite. If magma resides in a chamber for a period, then it can become stratified with lower density components rising to the top. Rocks accumulate in layers, forming a layered intrusion, additionally, the removal of the lower melting point components will tend to make the magma more viscous. If the magma is not vented to the surface in an eruption, it will slowly cool. Often, a volcano may have a deep magma chamber many kilometers down, as a volcano erupts, emptying the magma chamber, the surrounding rock will collapse into it. If a large amount of magma is erupted, causing the chamber to reduce considerably in volume, then this can result in a depression at the surface called a caldera
