A geologic map or geological map is a special-purpose map made to show geological features. Rock units or geologic strata are shown by color or symbols to indicate where they are exposed at the surface. Bedding planes and structural features such as faults, folds and lineations are shown with strike and dip or trend and plunge symbols which give these features' three-dimensional orientations. Stratigraphic contour lines may be used to illustrate the surface of a selected stratum illustrating the subsurface topographic trends of the strata. Isopach maps detail the variations in thickness of stratigraphic units, it is not always possible to properly show this when the strata are fractured, mixed, in some discontinuities, or where they are otherwise disturbed. Rock units are represented by colors. Instead of colors, certain symbols can be used. Different geologic mapping agencies and authorities have different standards for the colors and symbols to be used for rocks of differing types and ages. Geologists take two major types of orientation measurements: orientations of planes and orientations of lines.
Orientations of planes are measured as a "strike" and "dip", while orientations of lines are measured as a "trend" and "plunge". Strike and dip symbols consist of a long "strike" line, perpendicular to the direction of greatest slope along the surface of the bed, a shorter "dip" line on side of the strike line where the bed is going downwards; the angle that the bed makes with the horizontal, along the dip direction, is written next to the dip line. In the azimuthal system and dip are given as "strike/dip". Trend and plunge are used for linear features, their symbol is a single arrow on the map; the arrow is oriented in the downgoing direction of the linear feature and at the end of the arrow, the number of degrees that the feature lies below the horizontal is noted. Trend and plunge are notated as PLUNGE → TREND; the oldest preserved geologic map is the Turin papyrus, which shows the location of building stone and gold deposits in Egypt. The earliest geologic map of the modern era is the 1771 "Map of Part of Auvergne, or figures of, The Current of Lava in which Prisms, Etc. are Made from Basalt.
To be used with Mr. Demarest's theories of this hard basalt. Engraved by Messr. Pasumot and Daily, Geological Engineers of the King." This map is based on Nicolas Desmarest's 1768 detailed study of the geology and eruptive history of the Auvergne volcanoes and a comparison with the columns of the Giant's Causeway of Ireland. He identified both landmarks as features of extinct volcanoes; the 1798 report was incorporated in the 1771 Royal Academy of Science compendium. The first geological map of the U. S. was produced in 1809 by William Maclure. In 1807, Maclure undertook the self-imposed task of making a geological survey of the United States, he mapped nearly every state in the Union. During the rigorous two-year period of his survey, he crossed and recrossed the Allegheny Mountains some 50 times. Maclure's map shows the distribution of five classes of rock in what are now only the eastern states of the present-day US; the first geologic map of Great Britain was created by William Smith in 1815 using principles first formulated by Smith.
In the United States, geologic maps are superimposed over a topographic map with the addition of a color mask with letter symbols to represent the kind of geologic unit. The color mask denotes the exposure of the immediate bedrock if obscured by soil or other cover; each area of color denotes a geologic unit or particular rock formation. However, in areas where the bedrock is overlain by a thick unconsolidated burden of till, terrace sediments, loess deposits, or other important feature, these are shown instead. Stratigraphic contour lines, fault lines and dip symbols, are represented with various symbols as indicated by the map key. Whereas topographic maps are produced by the United States Geological Survey in conjunction with the states, geologic maps are produced by the individual states. There are no geologic map resources for some states, while a few states, such as Kentucky and Georgia, are extensively mapped geologically. In the United Kingdom the term geological map is used; the UK and Isle of Man have been extensively mapped by the British Geological Survey since 1835.
Two 1:625,000 scale maps cover the basic geology for the UK. More detailed sheets are available at scales of 1:250,000, 1:50,000 and 1:10,000; the 1:625,000 and 1:250,000 scales show both onshore and offshore geology, whilst other scales cover exposures on land only. Sheets of all scales fall into two categories: Superficial deposit maps show both bedrock and the deposits on top of it. Bedrock maps show the underlying rock, without superficial deposits; the maps are superimposed over a topographic map base produced by Ordnance Survey, use symbols to represent fault lines and dip or geological units, boreholes etc. Colors are used to represent different geological units. Explanatory booklets (
A ridge or a mountain ridge is a geological feature consisting of a chain of mountains or hills that form a continuous elevated crest for some distance. The sides of the ridge slope away from narrow top on either side; the line along the crest formed by the highest points, with the terrain dropping down on either side, is called the ridgeline. Ridges are termed hills or mountains as well, depending on size. There are several main types of ridges: Dendritic ridge: In typical dissected plateau terrain, the stream drainage valleys will leave intervening ridges; these are by far the most common ridges. These ridges represent more erosion resistant rock, but not always – they remain because there were more joints where the valleys formed or other chance occurrences; this type of ridge is somewhat random in orientation changing direction often with knobs at intervals on the ridge top. Stratigraphic ridge: In places such as the Ridge-and-Valley Appalachians, long straight ridges are formed because they are the uneroded remaining edges of the more resistant dipping strata that were folded laterally.
Similar ridges have formed in places such as the Black Hills, where the ridges form concentric circles around the igneous core. Sometimes these ridges are called "hogback ridges". Oceanic spreading ridge: In tectonic spreading zones around the world, such as at the Mid-Atlantic Ridge, the volcanic activity forms new land between tectonic boundaries creating volcanic ridges at the spreading zone. Isostatic settling and erosion reduces the elevations moving away from the zone. Crater ridges: Large meteorite strikes form large impact craters bordered by circular ridges. Volcanic crater/caldera ridges: Large volcanoes leave behind a central crater/caldera bordered by circular ridges. Fault ridges: Faults form escarpments. Sometimes the tops of the escarpments form not plateaus but slope back so that the edges of the escarpments form ridges. Dune ridges: In areas of large-scale dune activity, certain types of dunes result in sand ridges. Moraines and eskers: Glacial activity may leave ridges in the form of moraines and eskers.
An arête is a thin ridge of rock, formed by glacial erosion. Volcanic subglacial ridges: Many subglacial volcanoes create ridge-like formations when lava erupts through a thick glacier or ice sheet. Shutter ridges: A shutter ridge is a ridge which has moved along a fault line, blocking or diverting drainage. A shutter ridge creates a valley corresponding to the alignment of the fault that produces it. Pressure ridges: Also known as a tumuli develops in lava flows when slow-moving lava beneath a solidified crust wells upward; the brittle crust buckles to accommodate the inflating core of the flow, thus creating a central crack along the length of the tumulus. An Ice pressure ridge develops in an ice cover as a result of a stress regime established within the plane of the ice. Tectonic uplift – The portion of the total geologic uplift of the mean earth surface, not attributable to an isostatic response to unloading Mountain range – A geographic area containing several geologically related mountains Mountain chain Hill chain Norsk Geologisk Tidsskrift, Volume 69 Universitetsforlaget, 1989 page 40 https://books.google.com/books?id=dXK7AAAAIAAJ Physical Geography: Introduction To Earth page 164 https://books.google.com/books?id=dC7qhGQpBYkC
Yakutsk is the capital city of the Sakha Republic, located about 450 kilometers south of the Arctic Circle. Yakutsk, with an average temperature of −8.8 °C, is the second coldest city with more than 100,000 inhabitants in the world after Norilsk, although Yakutsk experiences colder temperatures in the winter. Yakutsk is the largest city located in continuous permafrost and one of the largest that cannot be reached by road. Yakutsk is a major port on the Lena River, it is served by the Yakutsk Airport as well as the smaller Magan Airport. The Yakuts known as the Sakha people, migrated to the area during the 13th and 14th centuries from other parts of Siberia; when they arrived they mixed with other indigenous Siberians in the area. The Russian settlement of Yakutsk was founded in 1632 as an ostrog by Pyotr Beketov. In 1639, it became the center of a voyevodstvo; the Voyevoda of Yakutsk soon became the most important Russian official in the region and directed expansion to the east and south. With an extreme subarctic climate, Yakutsk has the coldest winter temperatures for any major city on Earth.
Average monthly temperatures in Yakutsk range from +19.5 °C in July to −38.6 °C in January, only Norilsk has a lower mean annual temperature than any other settlement of over 100,000. Yakutsk is the largest city built on continuous permafrost, many houses there are built on concrete piles; the lowest temperatures recorded on the planet outside Antarctica occurred in the basin of the Yana River to the northeast of Yakutsk, making it the coldest major city in the world. Although winters are cold and long – Yakutsk has never recorded a temperature above freezing between 10 November and 14 March inclusive – summers are warm, with daily maximum temperatures exceeding +30 °C, making the seasonal temperature differences for the region the greatest in the world at 105 °C; the lowest temperature recorded in Yakutsk was −64.4 °C on 5 February 1891 and the highest temperatures +38.4 °C on 17 July 2011 and +38.3 °C on 15 July 1943. The hottest month in records going back to 1834 has been July 1894, with a mean of +23.2 °C, the coldest, January 1900, which averaged −51.2 °C.
Yakutsk has a distinct inland location, being 1,000 kilometres from the Pacific Ocean, which coupled with the high latitude means exposure to severe winters and lack of temperature moderation. July temperatures soar to an above-normal average for this parallel, with the average being several degrees hotter than such more southerly Far East cities as Vladivostok or Yuzhno-Sakhalinsk; the July daytime temperatures are hotter than some marine subtropical areas. The warm summers ensure; the climate is quite dry, with most of the annual precipitation occurring in the warmest months, due to the intense Siberian High forming around the cold continental air during the winter. However, summer precipitation is not heavy since the moist southeasterly winds from the Pacific Ocean lose their moisture over the coastal mountains well before reaching the Lena valley. With the Lena River navigable in the summer, there are various boat cruises offered, including upriver to the Lena Pillars, downriver tours which visit spectacular scenery in the lower reaches and the Lena delta.
Yakutia Airlines has its head office in the city. There are several theaters in Yakutsk: the State Russian Drama Theater, named after A. S. Pushkin. There are a number of museums as well: the National Fine Arts Museum of Sakha; the annual Ysyakh summer festival takes place the last weekend in June. The traditional Yakut summer solstice festivities include a celebration of the revival and renewal of the nature and beginning of a new year, it is accompanied by national Yakut rituals and ceremonies, folk dancing, horse racing, Yakut ethnic music and singing, national cuisine, competitions in traditional Yakut sports. There is a local punk scene in Yakutsk, with many bands. Shows can bring up to 300 people, young but older too. Yakutsk is the capital of the Sakha Republic; as an inhabited locality, Yakutsk is classified as a city under republic jurisdiction. Within the framework of administrative divisions, it is, together with the settlement of Zhatay and eleven rural localities, incorporated as the city of republic significance of Yakutsk—an administrative unit with a status equal to that of the districts.
As a municipal division and the eleven rural localities are incorporated as Yakutsk Urban Okrug. The settlement of Zhatay is not a part of Yakutsk Urban Okrug and is independently incorporated as Zhatay Urban Okrug. Divisional source:Population source:*Administrative centers are shown in bold Yakutsk is a destination of the Lena Highway; the city's connection to that highway is only usable by ferry in the summer, or in the dead of winter, by driving directly over the frozen Lena River, since Yakutsk lies on its western bank, there is no bridge anywhere in the Sakha Republic that crosses the Lena. The river is impassable for long periods of the year when it contains loose ice, when the ice cover is not thick enough to support traffic, or when the water level is too high and the river is turbulent with spring f
Khabarovsk Krai is a federal subject of Russia. It is geographically located in the Far East region of the country and is a part of the Far Eastern Federal District; the administrative center of the krai is the city of Khabarovsk, home to half of the krai's population and the second largest city in the Russian Far East. Khabarovsk Krai is the fourth-largest federal subject by area, with a population of 1,343,869 as of the; the southern region lies in the basin of the lower Amur River, with the mouth of the river located at Nikolaevsk-on-Amur draining into the Strait of Tartary, which separates Khabarovsk Krai from the island of Sakhalin. The north occupies a vast mountainous area along the coastline of the Sea of Okhotsk, a marginal sea of the Pacific Ocean. Khabarovsk Krai is bordered by Magadan Oblast to the north, Amur Oblast, Jewish Autonomous Oblast and the Sakha Republic to the west, Primorsky Krai to the south, Sakhalin Oblast to the east; the population is ethnic Russians, but indigenous people of the area are various Tungusic peoples and Amur Nivkhs.
Khabarovsk Krai shares its borders with Magadan Oblast in the north, with the Sakha Republic and Amur Oblast in the west, with the Jewish Autonomous Oblast and Primorsky Krai in the south, is limited by the Sea of Okhotsk in the east. In terms of area, it is the fourth-largest federal subject within Russia. Major islands include Shantar Islands. Taiga and tundra in the north, swampy forest in the central depression, deciduous forest in the south are the natural vegetation in the area. Khabarovsk Krai has a continental climate with its northern areas being subarctic with stronger maritime summer moderation in the north. In its southerly areas inland, annual swings are strong, with Khabarovsk itself having hot and humid summers which transforms into cold and long winters, where temperatures hardly go above freezing; this is because of the influence of the East Asian monsoon in summer and the bitterly cold Siberian High in winter. The second largest city of Komsomolsk-on-Amur has more violent temperature swings than Khabarovsk with winter average lows below −30 °C but in spite of this avoiding being subarctic because of the significant heat in shoulder seasons.
There are a number of peninsulas along the Krai's extensive coast, the main ones being the Lisyansky Peninsula, Nurki Peninsula, Tugurskiy Peninsula and the Tokhareu Peninsula. The main islands of Khabarovsk Krai are Malminskiye Island, the Shantar Islands, Menshikov Island, Reyneke Island, Chkalov Island, Baydukov Island and the Chastye Islands; the island of Sakhalin is administered separately as Sakhalin Oblast, along with the Kuril Islands. According to various Chinese and Korean records, the southern part of Khabarovsk Krai was occupied by one of the five semi-nomadic Shiwei, the Bo Shiwei tribes and the Black Water Mohe tribes living on the west and the east of the Bureinsky and the Lesser Khingan ranges. In 1643, Vassili Poyarkov's boats descended the Amur, returning to Yakutsk by the Sea of Okhotsk and the Aldan River, in 1649–1650 Yerofey Khabarov occupied the banks of the Amur; the resistance of the Chinese, obliged the Cossacks to quit their forts, by the Treaty of Nerchinsk Russia abandoned her advance into the basin of the river.
Although the Russians were thus deprived of the right to navigate the Amur River, the territorial claim over the lower courses of the river was not settled in the Treaty of Nerchinsk of 1689. The area between Uda River and Greater Khingan mountain range was left undemarcated and the Sino-Russian border was allowed to fluctuate. In the nineteenth century, Nikolay Muravyov would conduct an aggressive policy with China by claiming that the lower reaches of the Amur River belonged to Russia. In 1852, a Russian military expedition under Muravyov explored the Amur, by 1857 a chain of Russian Cossacks and peasants had been settled along the whole course of the river. In 1858, in the Treaty of Aigun, China recognized the Amur River downstream as far as the Ussuri River as the boundary between Russia and the Qing Empire, granted Russia free access to the Pacific Ocean; the Sino-Russian border was further delineated in the Treaty of Peking of 1860 when the Ussuri Territory, a joint possession, became Russian.
Modern Khabarovsk Krai was established on October 20, 1938, when the Far Eastern Krai was split into the Khabarovsk and Primorsky Krais. During the Soviet period, the high authority in the oblast was shared between three persons: The first secretary of the Khabarovsk CPSU Committee, the chairman of the oblast Soviet, the Chairman of the oblast Executive Committee. Since 1991, CPSU lost all the power, the head of the Oblast administration, the governor was appointed/elected alongside elected regional parliament; the Charter of Khabarovsk Krai is the fundamental law of the krai. The Legislative Duma of Khabarovsk Krai is the regional standing legislative body; the Legislative Duma exercises its authority by passing laws and other legal acts and by supervising the implementation and observance of the laws and other legal acts passed by it. The highest executive body is the Krai Government, which includes territorial executive bodies such as district administrations and commissions that facilita
Platinum is a chemical element with symbol Pt and atomic number 78. It is a dense, ductile unreactive, silverish-white transition metal, its name is derived from the Spanish term platino, meaning "little silver". Platinum is a member of the platinum group of elements and group 10 of the periodic table of elements, it has six occurring isotopes. It is one of the rarer elements in Earth's crust, with an average abundance of 5 μg/kg, it occurs in some nickel and copper ores along with some native deposits in South Africa, which accounts for 80% of the world production. Because of its scarcity in Earth's crust, only a few hundred tonnes are produced annually, given its important uses, it is valuable and is a major precious metal commodity. Platinum is one of the least reactive metals, it has remarkable resistance to corrosion at high temperatures, is therefore considered a noble metal. Platinum is found chemically uncombined as native platinum; because it occurs in the alluvial sands of various rivers, it was first used by pre-Columbian South American natives to produce artifacts.
It was referenced in European writings as early as 16th century, but it was not until Antonio de Ulloa published a report on a new metal of Colombian origin in 1748 that it began to be investigated by scientists. Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, jewelry. Being a heavy metal, it leads to health problems upon exposure to its salts. Compounds containing platinum, such as cisplatin and carboplatin, are applied in chemotherapy against certain types of cancer; as of 2018, the value of platinum is $833.00 per ounce. Pure platinum is a lustrous and malleable, silver-white metal. Platinum is more ductile than gold, silver or copper, thus being the most ductile of pure metals, but it is less malleable than gold; the metal has excellent resistance to corrosion, is stable at high temperatures and has stable electrical properties. Platinum does oxidize, forming PtO2, at 500 °C, it reacts vigorously with fluorine at 500 °C to form platinum tetrafluoride.
It is attacked by chlorine, bromine and sulfur. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in hot aqua regia, to form chloroplatinic acid, H2PtCl6, its physical characteristics and chemical stability make it useful for industrial applications. Its resistance to wear and tarnish is well suited to use in fine jewellery; the most common oxidation states of platinum are +2 and +4. The +1 and +3 oxidation states are less common, are stabilized by metal bonding in bimetallic species; as is expected, tetracoordinate platinum compounds tend to adopt 16-electron square planar geometries. Although elemental platinum is unreactive, it dissolves in hot aqua regia to give aqueous chloroplatinic acid: Pt + 4 HNO3 + 6 HCl → H2PtCl6 + 4 NO2 + 4 H2OAs a soft acid, platinum has a great affinity for sulfur, such as on dimethyl sulfoxide. In 2007, Gerhard Ertl won the Nobel Prize in Chemistry for determining the detailed molecular mechanisms of the catalytic oxidation of carbon monoxide over platinum.
Platinum has six occurring isotopes: 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, 198Pt. The most abundant of these is 195 Pt, it is the only stable isotope with a non-zero spin. 190Pt is the least abundant at only 0.01%. Of the occurring isotopes, only 190Pt is unstable, though it decays with a half-life of 6.5×1011 years, causing an activity of 15 Bq/kg of natural platinum. 198 Pt can undergo alpha decay. Platinum has 31 synthetic isotopes ranging in atomic mass from 166 to 204, making the total number of known isotopes 39; the least stable of these is 166Pt, with a half-life of 300 µs, whereas the most stable is 193Pt with a half-life of 50 years. Most platinum isotopes decay by some combination of beta alpha decay. 188Pt, 191Pt, 193Pt decay by electron capture. 190Pt and 198Pt are predicted to have energetically favorable double beta decay paths. Platinum is an rare metal, occurring at a concentration of only 0.005 ppm in Earth's crust. It is sometimes mistaken for silver. Platinum is found chemically uncombined as native platinum and as alloy with the other platinum-group metals and iron mostly.
Most the native platinum is found in secondary deposits in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum-group metals. Another large alluvial deposit is in the Ural Mountains, it is still mined. In nickel and copper deposits, platinum-group metals occur as sulfides, tellurides and arsenides, as end alloys with nickel or copper. Platinum arsenide, sperrylite, is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. At Platinum, about 17,000 kg was mined between 1927 and 1975; the mine ceased operations in 1990. The rare sulfide minera
The Japan Aerospace Exploration Agency is the Japanese national aerospace and space agency. Through the merger of three independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into orbit, is involved in many more advanced missions such as asteroid exploration and possible manned exploration of the Moon, its motto is One its corporate slogan is Explore to Realize. On 1 October 2003, three organizations were merged to form the new JAXA: Japan's Institute of Space and Astronautical Science, the National Aerospace Laboratory of Japan, National Space Development Agency of Japan. JAXA was formed as an Independent Administrative Institution administered by the Ministry of Education, Sports and Technology and the Ministry of Internal Affairs and Communications. Before the merger, ISAS was responsible for space and planetary research, while NAL was focused on aviation research. NASDA, founded on 1 October 1969, had developed rockets and built the Japanese Experiment Module.
The old NASDA headquarters were located at the current site of the Tanegashima Space Center, on Tanegashima Island, 115 kilometers south of Kyūshū. NASDA trained Japanese astronauts, who flew with the US Space Shuttles; the Basic Space Law was passed in 2008, the jurisdictional authority of JAXA moved from MEXT to the Strategic Headquarters for Space Development in the Cabinet, led by the Prime Minister. In 2016, the National Space Policy Secretariat was set up the Cabinet. In 2012, new legislation extended JAXA's remit from peaceful purposes only to include some military space development, such as missile early warning systems. Political control of JAXA passed from MEXT to the Prime Minister's Cabinet Office through a new Space Strategy Office. JAXA is composed of the following organizations: Space Technology Directorate I Space Technology Directorate II Human Spaceflight Technology Directorate Research and Development Directorate Aeronautical Technology Directorate Institute of Space and Astronautical Science Space Exploration Innovation Hub CenterJAXA has research centers in many locations in Japan, some offices overseas.
Its headquarters are in Tokyo. It has Earth Observation Research Center, Tokyo Earth Observation Center in Hatoyama, Saitama Noshiro Testing Center in Noshiro, Akita – Established in 1962, it carries out testing of rocket engines. Sanriku Balloon Center – Balloons have been launched from this site since 1971. Kakuda Space Center in Kakuda, Miyagi – Leads the development of rocket engines. Works with development of liquid fuel engines. Sagamihara Campus – Development of experimental equipment for rockets and satellites. Administrative buildings. Tanegashima Space Center – the launch site for the H-IIA and H-IIB rockets. Tsukuba Space Center in Tsukuba; this is the center of Japan's space network. It is involved in research and development of satellites and rockets, tracking and controlling of satellites, it develops experimental equipment for the Japanese Experiment Module. Training of astronauts takes place here. For International Space Station operations, the Japanese Flight Control Team is located at the Space Station Integration & Promotion Center in Tsukuba.
SSIPC communicates with ISS crewmembers via S-band audio. Uchinoura Space Center – the launch site for the Epsilon rocket. JAXA uses the H-IIA rocket from the former NASDA body and its variant H-IIB to launch engineering test satellites, weather satellites, etc. For science missions like X-ray astronomy, JAXA uses the Epsilon rocket. For experiments in the upper atmosphere JAXA uses the SS-520, S-520, S-310 sounding rockets. Prior to the establishment of JAXA, ISAS had been most successful in its space program in the field of X-ray astronomy during the 1980s and 1990s. Another successful area for Japan has been Very Long Baseline Interferometry with the HALCA mission. Additional success was achieved with solar observation and research of the magnetosphere, among other areas. NASDA was active in the field of communication satellite technology. However, since the satellite market of Japan is open, the first time a Japanese company won a contract for a civilian communication satellite was in 2005.
Another prime focus of the NASDA body is Earth climate observation. JAXA was awarded the Space Foundation's John L. "Jack" Swigert, Jr. Award for Space Exploration in 2008. Japan launched Ohsumi, in 1970, using ISAS' L-4S rocket. Prior to the merger, ISAS used small solid-fueled launch vehicles, while NASDA developed larger liquid-fueled launchers. In the beginning, NASDA used licensed American models; the first model of liquid-fuelled launch vehicle indigenously developed in Japan was the H-II, introduced in 1994. However, at the end of the 1990s, with two H-II launch failures, Japanese rocket technology began to face criticism. Japan's first space mission under JAXA, an H-IIA rocket launch on 29 November 2003, ended in failure due to stress problems. After a 15-month hiatus, JAXA performed a successful launch of an H-IIA rocket from Tanegashima Space Center, placing a satellite into orbit on 26 February 2005. In January 2017, JAXA attempted and failed to put a mini satellite into orbit atop one of its SS520 series rockets.
A second attempt on February 2, 2018 was successful, putting a 10-pound Cube
Intrusive rock is formed when magma crystallizes and solidifies underground to form intrusions, for example plutons, dikes, sills and volcanic necks. Intrusive rock forms within Earth's crust from the crystallization of magma. Many mountain ranges, such as the Sierra Nevada in California, are formed from large granite intrusions. Intrusions are one of the two ways igneous rock. Technically an intrusion is any formation of intrusive igneous rock. In contrast, an extrusion consists of extrusive rock. Large bodies of magma that solidify underground before they reach the surface of the crust are called plutons. Plutonic rocks form 7% of the Earth's current land surface. Coarse-grained intrusive igneous rocks that form at depth within the earth are called abyssal while those that form near the surface are called subvolcanic or hypabyssal. Intrusive structures are classified according to whether or not they are parallel to the bedding planes or foliation of the country rock: if the intrusion is parallel the body is concordant, otherwise it is discordant.
An intrusive suite is a group of plutons related in time and space.. Intrusions vary from mountain-range-sized batholiths to thin veinlike fracture fillings of aplite or pegmatite. Intrusions can be classified according to the shape and size of the intrusive body and its relation to the other formations into which it intrudes: Batholith: a large irregular discordant intrusion Chonolith: an irregularly-shaped intrusion with a demonstrable base Cupola: a dome-shaped projection from the top of a large subterranean intrusion Dike: a narrow tabular discordant body nearly vertical Laccolith: concordant body with flat base and convex top with a feeder pipe below Lopolith: concordant body with flat top and a shallow convex base, may have a feeder dike or pipe below Phacolith: a concordant lens-shaped pluton that occupies the crest of an anticline or trough of a syncline Volcanic pipe or volcanic neck: tubular vertical body that may have been a feeder vent for a volcano Sill: a thin tabular concordant body intruded along bedding planes Stock: a smaller irregular discordant intrusive Boss: a small stock A body of intrusive igneous rock which crystallizes from magma cooling underneath the surface of the Earth is called a pluton.
If the pluton is large, it may be called a stock. Intrusive rocks are characterized by large crystal sizes, as the individual crystals are visible, the rock is called phaneritic; this is as the magma cools underground, while cooling may be fast or slow, cooling is slower than on the surface, so larger crystals grow. If it runs parallel to rock layers, it is called a sill. If an intrusion makes rocks above rise to form a dome, it is called a laccolith. How deep-seated intrusions burst through the overlying strata causes intrusive rock to be recognized: Veins spread out into branches, or branchlike parts result from filled cracks, the high temperature is evident in how they alter country rock; as heat dissipation is slow, as the rock is under pressure, crystals form, no vitreous chilled matter is present. The intrusions did not flow. Contained gases could not escape through the thick strata, thus form cavities, which can be observed; because their crystals are of the rough equal size, these rocks are said to be equigranular.
There is no distinction between a first generation of large well-shaped crystals and a fine-grained ground-mass. The minerals of each have formed in a definite order, each has had a period of crystallization that may be distinct or may have coincided with or overlapped the period of formation of some of the other ingredients. Earlier crystals originated at a time when most of the rock was still liquid and are more or less perfect. Crystals are less regular in shape because they were compelled to occupy the spaces left between the already-formed crystals; the former case is said to be idiomorphic. There are many other characteristics that serve to distinguish the members of these two groups. For example, orthoclase is feldspar from granite, while its modifications occur in lavas of similar composition; the same distinction holds for nepheline varieties. Leucite is common in lavas but rare in plutonic rocks. Muscovite is confined to intrusions; these differences show the influence of the physical conditions under which consolidation takes place.
Intrusive rocks formed at greater depths are called abyssal. Some intrusive rocks solidified in fissures as dikes and intrusive sills at shallow depth and are called subvolcanic or hypabyssal, they show structures intermediate between those of plutonic rocks. They are commonly porphyritic and sometimes vesicular. In fact, many of them are petrologically indistinguishable from lavas of similar composition. Ellicott City Granodiorite Guilford Quartz Monzonite Methods of pluton emplacement Norbeck Intrusive Suite Volcanic rock Woodstock Quartz Monzonite