Krafla is a caldera of about 10 km in diameter with a 90 km long fissure zone, in the north of Iceland in the Mývatn region. Its highest peak reaches up to 818 m and it is 2 km in depth. There have been 29 reported eruptions in recorded history. Krafla includes the crater one of two well-known craters by this name in Iceland; the Icelandic word "víti" means "hell". In former times, people believed hell to be under volcanoes. Víti has a green lake inside of it. South of the Krafla area, but not within the caldera is Námafjall, a mountain, beneath, Hverir, a geothermal area with boiling mudpools and steaming fumaroles; the Mývatn fires occurred between 1724 -- 1729. The lava fountains could be seen in the south of the island and a lava flow destroyed three farms near the village of Reykjahlíð, although nobody was harmed. Between 1975 and 1984 there was a volcanic episode within the Krafla volcano, it involved fifteen uplift and subsidence events. This interrupted some of the Krafla drillfields. During these events a large magma chamber emerged.
This has been identified by analysing the seismic activity. Since 1977 the Krafla area has been the source of the geothermal energy used by a 60 MWe power station. A survey undertaken in 2006 indicated high temperatures at depths of between 3 and 5 kilometres and these favourable conditions have led to the development of the first well from the Iceland Deep Drilling Project, that found magma only 2.1 km deep. Geography of Iceland List of lakes of Iceland List of volcanoes in Iceland Volcanism in Iceland Geothermal power in Iceland Krafla in the Catalogue of Icelandic Volcanoes Volcanism Photos of Krafla and Reykjahlíð Univ. of Iceland: Information about Krafla Energy from magma at Krafla
Alaska is a U. S. state in the northwest extremity of North America, just across the Bering Strait from Asia. The Canadian province of British Columbia and territory of Yukon border the state to the east and southeast, its most extreme western part is Attu Island, it has a maritime border with Russia to the west across the Bering Strait. To the north are the Chukchi and Beaufort seas—southern parts of the Arctic Ocean; the Pacific Ocean lies to southwest. It is the largest U. S. state by the seventh largest subnational division in the world. In addition, it is the most sparsely populated of the 50 United States. Half of Alaska's residents live within the Anchorage metropolitan area. Alaska's economy is dominated by the fishing, natural gas, oil industries, resources which it has in abundance. Military bases and tourism are a significant part of the economy; the United States purchased Alaska from the Russian Empire on March 30, 1867, for 7.2 million U. S. dollars at two cents per acre. The area went through several administrative changes before becoming organized as a territory on May 11, 1912.
It was admitted as the 49th state of the U. S. on January 3, 1959. The name "Alaska" was introduced in the Russian colonial period when it was used to refer to the Alaska Peninsula, it was derived from an Aleut-language idiom. It means object to which the action of the sea is directed. Alaska is the northernmost and westernmost state in the United States and has the most easterly longitude in the United States because the Aleutian Islands extend into the Eastern Hemisphere. Alaska is the only non-contiguous U. S. state on continental North America. It is technically part of the continental U. S. but is sometimes not included in colloquial use. S. called "the Lower 48". The capital city, Juneau, is situated on the mainland of the North American continent but is not connected by road to the rest of the North American highway system; the state is bordered by Yukon and British Columbia in Canada, to the east, the Gulf of Alaska and the Pacific Ocean to the south and southwest, the Bering Sea, Bering Strait, Chukchi Sea to the west and the Arctic Ocean to the north.
Alaska's territorial waters touch Russia's territorial waters in the Bering Strait, as the Russian Big Diomede Island and Alaskan Little Diomede Island are only 3 miles apart. Alaska has a longer coastline than all the other U. S. states combined. Alaska is the largest state in the United States by total area at 663,268 square miles, over twice the size of Texas, the next largest state. Alaska is larger than all but 18 sovereign countries. Counting territorial waters, Alaska is larger than the combined area of the next three largest states: Texas and Montana, it is larger than the combined area of the 22 smallest U. S. states. There are no defined borders demarcating the various regions of Alaska, but there are six accepted regions: The most populous region of Alaska, containing Anchorage, the Matanuska-Susitna Valley and the Kenai Peninsula. Rural unpopulated areas south of the Alaska Range and west of the Wrangell Mountains fall within the definition of South Central, as do the Prince William Sound area and the communities of Cordova and Valdez.
Referred to as the Panhandle or Inside Passage, this is the region of Alaska closest to the rest of the United States. As such, this was where most of the initial non-indigenous settlement occurred in the years following the Alaska Purchase; the region is dominated by the Alexander Archipelago as well as the Tongass National Forest, the largest national forest in the United States. It contains the state capital Juneau, the former capital Sitka, Ketchikan, at one time Alaska's largest city; the Alaska Marine Highway provides a vital surface transportation link throughout the area, as only three communities enjoy direct connections to the contiguous North American road system. Designated in 1963; the Interior is the largest region of Alaska. Fairbanks is the only large city in the region. Denali National Park and Preserve is located here. Denali is the highest mountain in North America. Southwest Alaska is a sparsely inhabited region stretching some 500 miles inland from the Bering Sea. Most of the population lives along the coast.
Kodiak Island is located in Southwest. The massive Yukon–Kuskokwim Delta, one of the largest river deltas in the world, is here. Portions of the Alaska Peninsula are considered part of Southwest, with the remaining portions included with the Aleutian Islands; the North Slope is tundra peppered with small villages. The area is known for its massive reserves of crude oil, contains both the National Petroleum Reserve–Alaska and the Prudhoe Bay Oil Field; the city of Utqiagvik known as Barrow, is the northernmost city in the United States and is located here. The Northwest Arctic area, anchored by Kotzebue and containing the Kobuk River valley, is regarded as being part of this region. However, the respective Inupiat of the No
In geology, felsic refers to igneous rocks that are rich in elements that form feldspar and quartz. It is contrasted with mafic rocks, which are richer in magnesium and iron. Felsic refers to silicate minerals and rocks which are enriched in the lighter elements such as silicon, aluminium and potassium. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks are light in color and have specific gravities less than 3; the most common felsic rock is granite. Common felsic minerals include quartz, muscovite and the sodium-rich plagioclase feldspars. In modern usage, the term acid rock, although sometimes used as a synonym now refers to a high-silica-content volcanic rock, such as rhyolite. Older, broader usage is now considered archaic; that usage, with the contrasting term "basic rock", was based on an incorrect idea, dating from the 19th century, that "silicic acid" was the chief form of silicon occurring in rocks. The term "felsic" combines the words "feldspar" and "silica".
The similarity of the resulting term felsic to the German felsig, "rocky", is purely accidental. Feldspar is linked to German, it is a borrowing of Feldspat. The link is therefore to German Feld, meaning "field". In order for a rock to be classified as felsic, it needs to contain more than 75% felsic minerals. Rocks with greater than 90% felsic minerals can be called leucocratic, from the Greek words for white and dominance. Felsite is a petrologic field term used to refer to fine-grained or aphanitic, light-colored volcanic rocks which might be reclassified after a more detailed microscopic or chemical analysis. In some cases, felsic volcanic rocks may contain phenocrysts of mafic minerals hornblende, pyroxene or a feldspar mineral, may need to be named after their phenocryst mineral, such as'hornblende-bearing felsite'; the chemical name of a felsic rock is given according to the TAS classification of Le Maitre. However, this only applies to volcanic rocks. If the rock is analyzed and found to be felsic but is metamorphic and has no definite volcanic protolith, it may be sufficient to call it a'felsic schist'.
There are examples known of sheared granites which can be mistaken for rhyolites. For phaneritic felsic rocks, the QAPF diagram should be used, a name given according to the granite nomenclature; the species of mafic minerals is included in the name, for instance, hornblende-bearing granite, pyroxene tonalite or augite megacrystic monzonite, because the term "granite" assumes content with feldspar and quartz. The rock texture thus determines the basic name of a felsic rock. QAPF diagram List of minerals List of rock types Bowen's reaction series Archean felsic volcanic rocks Le Maitre, L. E. ed. 2002. Igneous Rocks: A Classification and Glossary of Terms 2nd edition, Cambridge
The Thuringian Forest, is a mountain range in the southern parts of the German state of Thuringia, running northwest to southeast between the valley of the river Werra near Eisenach and the Thuringian-Vogtlandian Slate Mountains. The geographical boundary with the latter range follows a line from Gehren via Großbreitenbach to Schönbrunn near Schleusingen, defined by the rivers Schleuse and Neubrunn on the southwestern slope, Talwasser, Wohlrose and Möhre on the northeastern slope; the Thuringian Forest forms a continuous chain of ancient rounded mountains with steep slopes to both sides and poses ample difficulties in transit routing save through a few navigable passes. It is 20 km wide; the highest elevation is Großer Beerberg at 982 m a.s.l. The Rennsteig is an ancient path connecting the summits, it is now a famous hiking path and marks the traditional boundary between the hills-dominated terrain of central Germany and the more rugged terrain characteristic of southern Germany, the boundary between the cultural regions of central and north Thuringia and Franconia.
Dialects and traditional customs and costumes are different on either side of the Rennsteig. The Rennsteig is the subject of the unofficial hymn of Thuringia. Motorway A 4 passes north of the Thuringian Forest, while A 71, intersecting the former south of Erfurt, crosses the range from the northeast to the southwest, passes under the ridge in the Rennsteig Tunnel near Oberhof, is joined near Suhl by A 73. Two more long-distance roads, Bundesstraßen 19 and 84, pass over the western parts of the range, while Bundesstraße 88 skirts the northern foothills between Eisenach and Geraberg; the Neudietendorf–Ritschenhausen railway crosses the Thuringian Forest in Brandleite Tunnel between Gehlberg and Oberhof, the Werra Railway between Eisenach and Eisfeld does so in a tunnel near Förtha. Both are in daily operation. A third line, the southern section of the Plaue–Themar railway, does not use a tunnel, but crosses the mountain ridge at Rennsteig switchback station, it has only been used by museum trains since 1998.
The Nuremberg–Erfurt high-speed railway, due to be commissioned in December 2017, crosses the Thuringian Forest with the help of several tunnels and bridges. Thüringerwaldbahn, a cross-country line of the Gotha tramway network, serves the northern foothills of the Thuringian Forest between Gotha and Bad Tabarz, including a branch to Waltershausen. Geologically, the Thuringian Forest is defined by a belt of uplifted and deformed metamorphic and igneous rock that divides the flat sedimentary plains of the Thüringer Becken from similar rock formations in the valley of the Werra, it consists of a large fault block in hercynian orientation, which consists from sandstones and conglomerates of Rotliegend age in its western parts, followed by granites and gneisses of the Ruhlaer Kristallin formation of early paleozoic origin which were uplifted in the Rotliegend era, the conglomerates and abundant volcanic rocks of the Oberhof trough. Ore deposits associated with the upthrust of the range have been of significant historical importance in the development of the region, for example, the metalworking tradition in Suhl and the mining history of Ilmenau.
The uplift of the horst-like fault block was part of the Saxonian tectonic processes and is understood as a long range effect of the Alpine orogeny. It ended in the late Tertiary after about 40 million years. Thuringian forest is surrounded on three sides by triassic rocks: the Thuringian Basin in the northeast, the Hesse Highlands in the west, the northeastern parts of the South German Scarplands in the south, by the Variscan rocks of the Thuringian Highland towards the east; the geological borders differ from the geographical ones insofar, as the Rotliegend rock of the Thuringian forest finds its continuation in the Masserberg and Crock block in Hildburghausen district, southeast of the main range, the rock types of the Thuringian Highland are found in the Schleuse horst between Schönbrunn reservoir and Schönau, in the Vesser complex near Schmiedefeld, an island of Variscan rocks embedded in Rotliegend. While the near-surface rocks of the Thuringian Highland comprise the folded Variscan basement, the oldest unfolded overlying strata of this basement are exposed in the Thuringian forest.
Common to both ranges, but to other low mountain ranges in Central Europe uplifted at the same time, are the bordering Zechstein deposits which contain Bryozoa reefs. These stretch wide on the northwestern edge of the Thuringian forest, where the landscape park of Altenstein Palace is located on one of the largest Zechstein reefs in Germany; the Eisenach trough is part of the much larger Werra basin, which in turn is part of the Saar-Unstrut depression of early Permian origin. It was uplifted as one of the fault blocks in the Saxonian tectonic era and is filled with Variscan molasses, named Eisenach formation after the location, it consists of monotonous sequences of reddish conglomerates representing a proximal alluvial fan which originated in debris flows from the Ruhla anticline. Dated in the upper Rotliegend, the Eisenach formation consists of some of the youngest geological units in the Thuringian forest; the lack of volcanic rocks suggests that at the time of the deposition of the Eisenach formation, no significant tectonic prosesses took place in the Werra basin, by a consolidated depositional environment.
In the Ruhla anticline the basement rocks
Papua New Guinea
Papua New Guinea the Independent State of Papua New Guinea, is an Oceanian country that occupies the eastern half of the island of New Guinea and its offshore islands in Melanesia, a region of the southwestern Pacific Ocean north of Australia. Its capital, located along its southeastern coast, is Port Moresby; the western half of New Guinea forms the Indonesian provinces of West Papua. At the national level, after being ruled by three external powers since 1884, Papua New Guinea established its sovereignty in 1975; this followed nearly 60 years of Australian administration, which started during World War I. It became an independent Commonwealth realm in 1975 with Elizabeth II as its queen, it became a member of the Commonwealth of Nations in its own right. Papua New Guinea is one of the most culturally diverse countries in the world, it is one of the most rural, as only 18 per cent of its people live in urban centres. There are 851 known languages in the country. Most of the population of more than 8 million people lives in customary communities, which are as diverse as the languages.
The country is one of the world's least explored and geographically. It is known to have numerous groups of uncontacted peoples, researchers believe there are many undiscovered species of plants and animals in the interior. Papua New Guinea is classified as a developing economy by the International Monetary Fund. Strong growth in Papua New Guinea's mining and resource sector led to the country becoming the sixth-fastest-growing economy in the world in 2011. Growth was expected to slow once major resource projects came on line in 2015. Mining remains a major economic factor, however. Local and national governments are discussing the potential of resuming mining operations at the Panguna mine in Bougainville Province, closed since the civil war in the 1980s–1990s. Nearly 40 per cent of the population lives a self-sustainable natural lifestyle with no access to global capital. Most of the people still live in strong traditional social groups based on farming, their social lives combine traditional religion including primary education.
These societies and clans are explicitly acknowledged by the Papua New Guinea Constitution, which expresses the wish for "traditional villages and communities to remain as viable units of Papua New Guinean society" and protects their continuing importance to local and national community life. The nation is an observer state in the Association of Southeast Asian Nations or ASEAN since 1976, has filed its application for full membership status, it is the Commonwealth of Nations. Archaeological evidence indicates that humans first arrived in Papua New Guinea around 42,000 to 45,000 years ago, they were descendants of migrants out of Africa, in one of the early waves of human migration. Agriculture was independently developed in the New Guinea highlands around 7000 BC, making it one of the few areas in the world where people independently domesticated plants. A major migration of Austronesian-speaking peoples to coastal regions of New Guinea took place around 500 BC; this has been correlated with the introduction of pottery and certain fishing techniques.
In the 18th century, traders brought the sweet potato to New Guinea, where it was adopted and became part of the staples. Portuguese traders had introduced it to the Moluccas; the far higher crop yields from sweet potato gardens radically transformed traditional agriculture and societies. Sweet potato supplanted the previous staple and resulted in a significant increase in population in the highlands. Although by the late 20th century headhunting and cannibalism had been eradicated, in the past they were practised in many parts of the country as part of rituals related to warfare and taking in enemy spirits or powers. In 1901, on Goaribari Island in the Gulf of Papua, missionary Harry Dauncey found 10,000 skulls in the island's long houses, a demonstration of past practices. According to Marianna Torgovnick, writing in 1991, "The most documented instances of cannibalism as a social institution come from New Guinea, where head-hunting and ritual cannibalism survived, in certain isolated areas, into the Fifties and Seventies, still leave traces within certain social groups."Little was known in Europe about the island until the 19th century, although Portuguese and Spanish explorers, such as Dom Jorge de Menezes and Yñigo Ortiz de Retez, had encountered it as early as the 16th century.
Traders from Southeast Asia had visited New Guinea beginning 5,000 years ago to collect bird-of-paradise plumes. The country's dual name results from its complex administrative history before independence; the word papua is derived from an old local term of uncertain origin. "New Guinea" was the name coined by the Spanish explorer Yñigo Ortiz de Retez. In 1545, he noted the resemblance of the people to those he had earlier seen along the Guinea coast of Africa. Guinea, in its turn, is etymologically derived from the Portuguese word Guiné; the name is one of several toponyms sharing similar etymologies meaning "land of the blacks" or similar meanings, in reference to the dark skin of the inhabitants. In the nineteenth century, Germany ruled the northern half of the country for some decades, beginning in 1884, as a colony named German New Guinea. In 1914 after the outbreak of World War I, Australian forces landed and captured German New Guinea in a small military campaign and occupied it throughout the war.
After the war, in which Germany and the Central Pow
Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava; the magma can be crust. The melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form natural glasses. Igneous rocks occur in a wide range of geological settings: shields, orogens, large igneous provinces, extended crust and oceanic crust. Igneous and metamorphic rocks make up 90–95% of the top 16 km of the Earth's crust by volume. Igneous rocks form about 15% of the Earth's current land surface. Most of the Earth's oceanic crust is made of igneous rock. Igneous rocks are geologically important because: their minerals and global chemistry give information about the composition of the mantle, from which some igneous rocks are extracted, the temperature and pressure conditions that allowed this extraction, and/or of other pre-existing rock that melted.
In terms of modes of occurrence, igneous rocks can be either extrusive. Intrusive igneous rocks make up the majority of igneous rocks and are formed from magma that cools and solidifies within the crust of a planet, surrounded by pre-existing rock; the mineral grains in such rocks can be identified with the naked eye. Intrusive rocks can be classified according to the shape and size of the intrusive body and its relation to the other formations into which it intrudes. Typical intrusive formations are batholiths, laccoliths and dikes; when the magma solidifies within the earth's crust, it cools forming coarse textured rocks, such as granite, gabbro, or diorite. The central cores of major mountain ranges consist of intrusive igneous rocks granite; when exposed by erosion, these cores may occupy huge areas of the Earth's surface. Intrusive igneous rocks that form at depth within the crust are termed plutonic rocks and are coarse-grained. Intrusive igneous rocks that form near the surface are termed subvolcanic or hypabyssal rocks and they are medium-grained.
Hypabyssal rocks are less common than plutonic or volcanic rocks and form dikes, laccoliths, lopoliths, or phacoliths. Extrusive igneous rocks known as volcanic rocks, are formed at the crust's surface as a result of the partial melting of rocks within the mantle and crust. Extrusive solidify quicker than intrusive igneous rocks, they are formed by the cooling of molten magma on the earth's surface. The magma, brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate. Hence such rocks are smooth and fine-grained. Basalt is lava plateaus; some kinds of basalt solidify to form long polygonal columns. The Giant's Causeway in Antrim, Northern Ireland is an example; the molten rock, with or without suspended crystals and gas bubbles, is called magma. It rises; when magma reaches the surface from beneath water or air, it is called lava. Eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine. Black smokers and mid-ocean ridge basalt are examples of submarine volcanic activity.
The volume of extrusive rock erupted annually by volcanoes varies with plate tectonic setting. Extrusive rock is produced in the following proportions: divergent boundary: 73% convergent boundary: 15% hotspot: 12%. Magma that erupts from a volcano behaves according to its viscosity, determined by temperature, crystal content and the amount of silica. High-temperature magma, most of, basaltic in composition, behaves in a manner similar to thick oil and, as it cools, treacle. Long, thin basalt flows with pahoehoe surfaces are common. Intermediate composition magma, such as andesite, tends to form cinder cones of intermingled ash and lava, may have a viscosity similar to thick, cold molasses or rubber when erupted. Felsic magma, such as rhyolite, is erupted at low temperature and is up to 10,000 times as viscous as basalt. Volcanoes with rhyolitic magma erupt explosively, rhyolitic lava flows are of limited extent and have steep margins, because the magma is so viscous. Felsic and intermediate magmas that erupt do so violently, with explosions driven by the release of dissolved gases—typically water vapour, but carbon dioxide.
Explosively erupted pyroclastic material is called tephra and includes tuff and ignimbrite. Fine volcanic ash is erupted and forms ash tuff deposits, which ca