Armenia, officially the Republic of Armenia, is a sovereign state in the South Caucasus region of Eurasia. The Republic of Armenia constitutes only one-tenth of historical Armenia, Armenia is a unitary, multi-party, democratic nation-state with an ancient cultural heritage. Urartu was established in 860 BC and by the 6th century BC it was replaced by the Satrapy of Armenia, in the 1st century BC the Kingdom of Armenia reached its height under Tigranes the Great. Armenia became the first state in the world to adopt Christianity as its official religion, in between the late 3rd century to early years of the 4th century, the state became the first Christian nation. The official date of adoption of Christianity is 301 AD. The ancient Armenian kingdom was split between the Byzantine and Sasanian Empires around the early 5th century, under the Bagratuni dynasty, the Bagratid Kingdom of Armenia was restored in the 9th century. Declining due to the wars against the Byzantines, the fell in 1045. An Armenian principality and a kingdom Cilician Armenia was located on the coast of the Mediterranean Sea between the 11th and 14th centuries.
By the 19th century, Eastern Armenia had been conquered by the Russian Empire, during World War I, Armenians living in their ancestral lands in the Ottoman Empire were systematically exterminated in the Armenian Genocide. By 1920, the state was incorporated into the Transcaucasian Socialist Federative Soviet Republic, in 1936, the Transcaucasian state was dissolved, transforming its constituent states, including the Armenian Soviet Socialist Republic, into full Union republics. The modern Republic of Armenia became independent in 1991 during the dissolution of the Soviet Union, the Republic of Armenia recognises the Armenian Apostolic Church, the worlds oldest national church, as the countrys primary religious establishment. The unique Armenian alphabet was invented by Mesrop Mashtots in 405 AD, Armenia is a member of the Eurasian Economic Union, the Council of Europe and the Collective Security Treaty Organization. Armenia supports the de facto independent Nagorno-Karabakh Republic, which was proclaimed in 1991, the native Armenian name for the country is Հայք.
The name in the Middle Ages was extended to Հայաստան, by addition of the Persian suffix -stan, the further origin of the name is uncertain. It is postulated that the name Hay comes from one of the two confederated, Hittite vassal states—the Ḫayaša-Azzi. The exonym Armenia is attested in the Old Persian Behistun Inscription as Armina, the ancient Greek terms Ἀρμενία and Ἀρμένιοι are first mentioned by Hecataeus of Miletus. Xenophon, a Greek general serving in some of the Persian expeditions, describes many aspects of Armenian village life and he relates that the people spoke a language that to his ear sounded like the language of the Persians. According to the histories of both Moses of Chorene and Michael Chamchian, Armenia derives from the name of Aram, a descendant of Hayk
A hill is a landform that extends above the surrounding terrain. It often has a summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit. The distinction between a hill and a mountain is unclear and largely subjective, but a hill is considered to be less tall. The Great Soviet Encyclopedia defines hill as an upland with a height up to 200 m. Today, a mountain is usually defined in the UK and Ireland as any summit at least 2,000 feet high, some definitions include a topographical prominence requirement, typically 100 feet or 500 feet. In practice, mountains in Scotland are frequently referred to as no matter what their height, as reflected in names such as the Cuillin Hills. In Wales, the distinction is more a term of land use, for a while, the U. S. defined a mountain as being 1,000 feet or more tall. Any similar landform lower than this height was considered a hill, the United States Geological Survey, has concluded that these terms do not in fact have technical definitions in the U. S. A hillock is a small hill, other words include knoll and its variant, knowe.
Artificial hills may be referred to by a variety of names, including mound. Various names used to describe types of hill, based on appearance and these include, Drumlin – an elongated whale-shaped hill formed by glacial action. Butte – an isolated hill with steep sides and a flat top. Kuppe – a rounded hill or low mountain, typical of central Europe Tor – a rock found on a hilltop, used to refer to the hill. Puy – used especially in the Auvergne, France, to describe a conical volcanic hill, pingo – a mound of earth-covered ice found in the Arctic and Antarctica. For example, Ancient Rome was built on seven hills, protecting it from invaders, in northern Europe, many ancient monuments are sited in heaps. Some of these are structures, but others appear to have hardly any significance. In Britain, many churches at the tops of hills are thought to have built on the sites of earlier pagan holy places. The National Cathedral in Washington, DC has followed this tradition and was built on the highest hill in that city, Hills provide a major advantage to an army, giving them an elevated firing position and forcing an opposing army to charge uphill to attack them
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water, small rivers can be referred to using names such as stream, brook and rill. There are no official definitions for the term river as applied to geographic features. Many names for small rivers are specific to geographic location, examples are run in parts of the United States, burn in Scotland and northeast England. Sometimes a river is defined as being larger than a creek, but not always, Rivers are part of the hydrological cycle. Potamology is the study of rivers while limnology is the study of inland waters in general. Extraterrestrial rivers of liquid hydrocarbons have recently found on Titan. Channels may indicate past rivers on other planets, specifically outflow channels on Mars and rivers are theorised to exist on planets, a river begins at a source, follows a path called a course, and ends at a mouth or mouths.
The water in a river is confined to a channel. In larger rivers there is a wider floodplain shaped by flood-waters over-topping the channel. Floodplains may be wide in relation to the size of the river channel. This distinction between river channel and floodplain can be blurred, especially in areas where the floodplain of a river channel can become greatly developed by housing. Rivers can flow down mountains, through valleys or along plains, the term upriver refers to the direction towards the source of the river, i. e. against the direction of flow. Likewise, the term describes the direction towards the mouth of the river. The term left bank refers to the bank in the direction of flow. The river channel typically contains a stream of water, but some rivers flow as several interconnecting streams of water. Extensive braided rivers are now found in only a few regions worldwide and they occur on peneplains and some of the larger river deltas. Anastamosing rivers are similar to braided rivers and are quite rare
The Mandara Mountains are a volcanic range extending about 200km along the northern part of the Cameroon-Nigeria border, from the Benue River in the south to the north-west of Maroua in the north. The highest elevation is 1,494 m, the summit of Mount Oupay, the region is densely populated, mainly by speakers of Chadic languages. The Mofu ethnic group lives in the Mandara Mountains, extensive archaeological research has been undertaken in the Mandara Mountains, including work at Diy-Gid-Biy sites
Weathering is the breaking down of rocks and minerals as well as wood and artificial materials through contact with the Earths atmosphere and biological organisms. Two important classifications of weathering processes exist – physical and chemical weathering, mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water and pressure. While physical weathering is accentuated in very cold or very dry environments, chemical reactions are most intense where the climate is wet, both types of weathering occur together, and each tends to accelerate the other. For example, physical abrasion decreases the size of particles and therefore increases their surface area, the various agents act in concert to convert primary minerals to secondary minerals and release plant nutrient elements in soluble forms. The materials left over after the rock breaks down combined with organic material creates soil, in addition, many of Earths landforms and landscapes are the result of weathering processes combined with erosion and re-deposition.
Physical weathering, recognized as mechanical weathering, is the class of processes that causes the disintegration of rocks without chemical change, the primary process in physical weathering is abrasion. However and physical weathering often go hand in hand, physical weathering can occur due to temperature, frost etc. For example, cracks exploited by physical weathering will increase the area exposed to chemical action. Abrasion by water and wind loaded with sediment can have tremendous cutting power, as is amply demonstrated by the gorges, ravines. In glacial areas, huge moving ice masses embedded with soil and rock fragments grind down rocks in their path, plant roots sometimes enter cracks in rocks and pry them apart, resulting in some disintegration, Burrowing animals may help disintegrate rock through their physical action. However, such influences are usually of importance in producing parent material when compared to the drastic physical effects of water, wind. Physical weathering is called mechanical weathering or disaggregation.
Thermal stress weathering results from the expansion and contraction of rock, for example, heating of rocks by sunlight or fires can cause expansion of their constituent minerals. As some minerals expand more than others, temperature changes set up differential stresses that cause the rock to crack apart. Because the outer surface of a rock is often warmer or colder than the more protected inner portions and this process may be sharply accelerated if ice forms in the surface cracks. When water freezes, it expands with a force of about 1465 Mg/m^2, disintegrating huge rock masses, thermal stress weathering comprises two main types, thermal shock and thermal fatigue. Thermal stress weathering is an important mechanism in deserts, where there is a diurnal temperature range, hot in the day. The repeated heating and cooling exerts stress on the layers of rocks
The theoretical model builds on the concept of continental drift developed during the first few decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s, the lithosphere, which is the rigid outermost shell of a planet, is broken up into tectonic plates. The Earths lithosphere is composed of seven or eight major plates, where the plates meet, their relative motion determines the type of boundary, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The relative movement of the plates typically ranges from zero to 100 mm annually, tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle, the material lost is balanced by the formation of new crust along divergent margins by seafloor spreading.
In this way, the surface of the lithosphere remains the same. This prediction of plate tectonics is referred to as the conveyor belt principle, earlier theories, since disproven, proposed gradual shrinking or gradual expansion of the globe. Tectonic plates are able to move because the Earths lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the ridge and drag, with downward suction. Another explanation lies in the different forces generated by forces of the Sun. The relative importance of each of these factors and their relationship to other is unclear. The outer layers of the Earth are divided into the lithosphere and asthenosphere and this is based on differences in mechanical properties and in the method for the transfer of heat. Mechanically, the lithosphere is cooler and more rigid, while the asthenosphere is hotter, in terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere transfers heat by convection and has a nearly adiabatic temperature gradient.
The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, Plate motions range up to a typical 10–40 mm/year, to about 160 mm/year. The driving mechanism behind this movement is described below, tectonic lithosphere plates consist of lithospheric mantle overlain by either or both of two types of crustal material, oceanic crust and continental crust. Average oceanic lithosphere is typically 100 km thick, its thickness is a function of its age, as passes, it conductively cools
It may be an example of a nunatak. Glaciers, typically forming in drainages on the sides of a mountain, cirque glaciers have rotational sliding that abrades the floor of the basin more than walls and that causes the bowl shape to form. As cirques are formed by glaciation in an environment, the headwall. This occurs due to freeze/thaw and mass wasting beneath the ice surface and it is widely held that a common cause for headwall steepening and extension headward is the crevasses known as bergschrund that occur between the moving ice and the headwall. Plucking and shattering can be here by those exploring the crevasses. A cirque is exposed when the glacier that created it recedes, when three or more of these cirques converge on a central point, they create a pyramid-shaped peak with steep walls. These horns are a shape for mountain tops in highly glaciated areas. The number of faces of a horn depends on the number of involved in the formation of the peak. Horns with more than four faces include the Weissmies and the Mönch, a peak with four symmetrical faces is called a Matterhorn The peak of a glacial horn will often outlast the arêtes on its flanks.
As the rock around it erodes, the gains in prominence. Eventually, a glacial horn will have vertical faces on all sides. In the Alps, horn is the name of very exposed peaks with slope inclinations of 45-60°, upper Saddle River, NJ, Prentice Hall. Illustrated Glossary of Alpine Glacial Landforms
It includes all phenomena resulting from and causing magma within the crust or mantle of the body, to rise through the crust and form volcanic rocks on the surface. Magma from the mantle or lower crust rises through its crust towards the surface, if magma reaches the surface, its behavior depends on the viscosity of the molten constituent rock. Viscous magma produces volcanoes characterised by explosive eruptions, while non-viscous magma produce volcanoes characterised by effusive eruptions pouring large amounts of lava onto the surface, in some cases, rising magma can cool and solidify without reaching the surface. Instead, the cooled and solidified igneous mass crystallises within the crust to form an igneous intrusion, as magma cools the chemicals in the crystals formed are effectively removed from the main mix of the magma, so the chemical content of the remaining magma evolves as it solidifies slowly. Fresh unevolved magma injections can remobilise more evolved magmas, allowing eruptions from more viscous magmas, movement of molten rock in the mantle, caused by thermal convection currents, coupled with gravitational effects of changes on the earths surface drive plate tectonic motion and ultimately volcanism.
Volcanoes are places where magma reaches the earths surface, the type of volcano depends on the location of the eruption and the consistency of the magma. These are formed where magma pushes between existing rock, intrusions can be in the form of batholiths, sills, earthquakes are generally associated with plate tectonic activity, but some earthquakes are generated as a result of volcanic activity. These are formed where water interacts with volcanism and these include geysers, fumaroles and mudpots, they are often used as a source of geothermal energy. The amount of gas and ash emitted by volcanic eruptions has a significant effect on the Earths climate, large eruptions correlate well with some significant climate change events. When the magma cools it solidifies and forms rocks, the type of rock formed depends on the composition of the magma. Magma that reaches the surface to become lava cools rapidly resulting in rocks with small crystals such as basalt, some of this magma may cool extremely rapidly and will form volcanic glass such as obsidian.
Magma that remains trapped below ground in thin intrusions cools slower than magma exposed to the surface, magma that remains trapped in large quantities below ground cools most slowly resulting in rocks with larger crystals - such as granite and gabbro. Existing rocks that come into contact with magma may be melted and assimilated into the magma, other rocks adjacent to the magma may be altered by contact metamorphism or metasomatism as they are affected by the heat and escaping or externally circulating hydrothermal fluids. Volcanism is not confined only to Earth, but is thought to be found on any body having a solid crust, evidence of volcanism should still be found on any body that has had volcanism at some point in its history. It can be surmised that volcanism exists on planets and moons of this type in other systems as well. In 2014, scientists found 70 lava flows which formed on the Moon in the last 100 million years, bimodal volcanism Continental drift Hotspot Volcanic arc Glossary of Volcanic Terms. G. J.
Hudak, University of Wisconsin Oshkosh,2001, crumpler, L. S. and Lucas, S. G. Volcanoes of New Mexico, An Abbreviated Guide For Non-Specialists. New Mexico Museum of Natural History and Science Bulletin, archived from the original on 2007-03-21
The Appalachian Mountains, often called the Appalachians, are a system of mountains in eastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period and it once reached elevations similar to those of the Alps and the Rocky Mountains before naturally occurring erosion. The Appalachian chain is a barrier to east-west travel, as it forms a series of alternating ridgelines, definitions vary on the precise boundaries of the Appalachians. A common variant definition does not include the Adirondack Mountains, which belong to the Grenville Orogeny and have a different geological history from the rest of the Appalachians. The range covers parts of the islands of Saint Pierre and Miquelon, the system is divided into a series of ranges, with the individual mountains averaging around 3,000 ft. The highest of the group is Mount Mitchell in North Carolina at 6,684 feet, the term Appalachian refers to several different regions associated with the mountain range.
Most broadly, it refers to the mountain range with its surrounding hills. The Ouachita Mountains in Arkansas and Oklahoma were originally part of the Appalachians as well, the name was soon altered by the Spanish to Apalachee and used as a name for the tribe and region spreading well inland to the north. Pánfilo de Narváezs expedition first entered Apalachee territory on June 15,1528, now spelled Appalachian, it is the fourth-oldest surviving European place-name in the US. After the de Soto expedition in 1540, Spanish cartographers began to apply the name of the tribe to the mountains themselves. The first cartographic appearance of Apalchen is on Diego Gutierrezs map of 1562, the name was not commonly used for the whole mountain range until the late 19th century. A competing and often more popular name was the Allegheny Mountains, Alleghenies, in the early 19th century, Washington Irving proposed renaming the United States either Appalachia or Alleghania. In U. S. dialects in the regions of the Appalachians.
In northern parts of the range, it is pronounced /ˌæpəˈleɪtʃᵻnz/ or /ˌæpəˈleɪʃᵻnz/, the third syllable is like lay. There is often debate between the residents of the regions as to which pronunciation is the more correct one. Elsewhere, a commonly accepted pronunciation for the adjective Appalachian is /ˌæpəˈlætʃiən/, the whole system may be divided into three great sections, The northern section runs from the Canadian province of Newfoundland and Labrador to the Hudson River. The Monteregian Hills, which cross the Green Mountains in Quebec, are unassociated with the Appalachians, The central section goes from the Hudson Valley to the New River running through Virginia and West Virginia. Southern, The southern section runs from the New River onwards and it consists of the prolongation of the Blue Ridge, which is divided into the Western Blue Ridge Front and the Eastern Blue Ridge Front, the Ridge-and-Valley Appalachians, and the Cumberland Plateau
A mountain is a large landform that stretches above the surrounding land in a limited area, usually in the form of a peak. A mountain is steeper than a hill. Mountains are formed through tectonic forces or volcanism and these forces can locally raise the surface of the earth. Mountains erode slowly through the action of rivers, weather conditions, a few mountains are isolated summits, but most occur in huge mountain ranges. High elevations on mountains produce colder climates than at sea level and these colder climates strongly affect the ecosystems of mountains, different elevations have different plants and animals. Because of the less hospitable terrain and climate, mountains tend to be used less for agriculture and more for resource extraction and recreation, the highest mountain on Earth is Mount Everest in the Himalayas of Asia, whose summit is 8,850 m above mean sea level. The highest known mountain on any planet in the Solar System is Olympus Mons on Mars at 21,171 m, there is no universally accepted definition of a mountain.
Elevation, relief, steepness and continuity have been used as criteria for defining a mountain, whether a landform is called a mountain may depend on local usage. The highest point in San Francisco, California, is called Mount Davidson, notwithstanding its height of 300 m, Mount Scott outside Lawton, Oklahoma is only 251 m from its base to its highest point. Whittows Dictionary of Physical Geography states Some authorities regard eminences above 600 metres as mountains, in addition, some definitions include a topographical prominence requirement, typically 100 or 500 feet. For a while, the US defined a mountain as being 1,000 feet or taller, any similar landform lower than this height was considered a hill. However, the United States Geological Survey concludes that these terms do not have technical definitions in the US, using these definitions, mountains cover 33% of Eurasia, 19% of South America, 24% of North America, and 14% of Africa. As a whole, 24% of the Earths land mass is mountainous, there are three main types of mountains, volcanic and block.
All three types are formed from plate tectonics, when portions of the Earths crust move, compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. The height of the feature makes it either a hill or, if higher and steeper, major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity. Volcanoes are formed when a plate is pushed below another plate, at a depth of around 100 km, melting occurs in rock above the slab, and forms magma that reaches the surface. When the magma reaches the surface, it builds a volcanic mountain. Examples of volcanoes include Mount Fuji in Japan and Mount Pinatubo in the Philippines, the magma does not have to reach the surface in order to create a mountain, magma that solidifies below ground can still form dome mountains, such as Navajo Mountain in the US
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 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, 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
Mean sea level is an average level of the surface of one or more of Earths oceans from which heights such as elevations may be measured. A common and relatively straightforward mean sea-level standard is the midpoint between a low and mean high tide at a particular location. Sea levels can be affected by factors and are known to have varied greatly over geological time scales. The careful measurement of variations in MSL can offer insights into ongoing climate change, the term above sea level generally refers to above mean sea level. Precise determination of a sea level is a difficult problem because of the many factors that affect sea level. Sea level varies quite a lot on several scales of time and this is because the sea is in constant motion, affected by the tides, atmospheric pressure, local gravitational differences, salinity and so forth. The easiest way this may be calculated is by selecting a location and calculating the mean sea level at that point, for example, a period of 19 years of hourly level observations may be averaged and used to determine the mean sea level at some measurement point.
One measures the values of MSL in respect to the land, hence a change in MSL can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates. In the UK, the Ordnance Datum is the sea level measured at Newlyn in Cornwall between 1915 and 1921. Prior to 1921, the datum was MSL at the Victoria Dock, in Hong Kong, mPD is a surveying term meaning metres above Principal Datum and refers to height of 1. 230m below the average sea level. In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and it is used for a part of continental Europe and main part of Africa as official sea level. Elsewhere in Europe vertical elevation references are made to the Amsterdam Peil elevation, satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001, height above mean sea level is the elevation or altitude of an object, relative to the average sea level datum.
It is used in aviation, where some heights are recorded and reported with respect to sea level, and in the atmospheric sciences. An alternative is to base height measurements on an ellipsoid of the entire Earth, in aviation, the ellipsoid known as World Geodetic System 84 is increasingly used to define heights, differences up to 100 metres exist between this ellipsoid height and mean tidal height. The alternative is to use a vertical datum such as NAVD88. When referring to geographic features such as mountains on a topographic map, the elevation of a mountain denotes the highest point or summit and is typically illustrated as a small circle on a topographic map with the AMSL height shown in metres, feet or both. In the rare case that a location is below sea level, for one such case, see Amsterdam Airport Schiphol