Datun volcanic eruption without endangering the Taipei

Earth a researcher at the Academia Sinica, Chen Zhonghua, said yesterday that the Datun volcano group activities like "sleeping volcano may erupt, currently in a dormant state.

Academia Sinica host the first World Research Conference, the Chen Zhonghua study volcanic ash deposited in the Taipei area, found Datun volcanic eruption in the past two million years, a total of four, and last about six thousand years ago, in line with the definition of internationally active volcano .

He said that the extinct volcano, the active volcano defined the volcanic easily misunderstood volcanic characteristics to the "active" and "inactive" distinction is more accurate. Active volcano eruption might, but that does not mean the danger of an immediate eruption, should strengthen monitoring and prepare for Disaster Reduction ".

Chen Zhonghua said, to volcanic magma activity status and past record of view, even if Datun volcano eruption, the affected area should also not be extended to the entire Taipei.

Researcher at the Academia Sinica Institute of Earth Sciences, Cheng-Horng Lin said, the volcano is divided into an active volcano, an extinct volcano, dormant volcano. Active volcanoes on behalf of eruptions or magma activities under a million years; extinct volcano magma or heat is no longer there, dormant volcano is quiet for a long time, but there are likely eruption.

He said that the the Datun volcano academia multi dormant active volcanoes. The National Science Council and other units established Datun Volcano Observatory, add inclinometer, crustal uplift changes can be detected.

Volcanic terrain

Volcanic skeleton 

 When volcanic activity ceased, the erosion of the role of then forthcoming, weak sediments are corrosion, and the remaining is to do some hard igneous veins standing surface, the volcanic terrain skeleton known as the volcano (Volcanic skeletons). Volcanic formation, first of all persons shall be eroded volcanic cone (Volcanic cones), cone contains many large volcanic quality, easy-permeable of these substances, it could enhance its corrosion resistance, and the volcanic cone for radial water system, as a result of Hill Cone considerable slope, rivers easy to cut, can form small canyon. After a long-term erosion of the volcanic cone, only a small number of hard rock residues, these remnants of the terrain to volcanic neck and dyke-feng (Dike ridges) is most common for the lava rock wall in the vertical by condensation into a rock, if the intrusion of the large number of magmatic material , the Diagenetic also has strength and corrosion resistance dyke generally weak, they can form mountain dyke; But Hill is not very rock wall and has a number of vertical tilt, then in appearance back Cliff like pig (Hog backs) , the difference between the two, mainly from the nature of the rocks on the start for the volcanic rock formed by the wall, pigs back is by the side of cliffs and steep rock formation. Dyke can not form a peak, if the rock wall of stone weaker than the surrounding rock, it vulnerable to erosion by weathering depression. 

 Low-lying volcanic terrain 

 Volcanic eruptions and fall, can be found in the crater area of the formation of low-lying land, the Composite Williams (Howel Williams) and search Algabid (TA Jaggar)'s classification of the two laws, these low-lying land can be divided into three categories: 

 

 Crater (Craters) 

 Volcano eruptions (Explosion craters) 

 There are side crater (Crater within constructed rims) 

 Fall crater (Collapse craters) 

 Volcanic acetabular (Calderas) 

 Acetabular volcanic eruption (Explorsion calderas) 

 Subsidence volcano acetabular (Subsidence calderas) 

 Composite volcano acetabular (Composite calderas) 

 Volcanic tectonic depressions (Volcanic-tectonic depressions) 

 Acetabular crater and volcanic eruptions are the mouth, but both of different shapes, so the names are different, their differences are as follows: 

 a. crater size, often less than a mile in diameter, volcanic area of the acetabulum, and a few miles in diameter to tens of miles. 

 b. crater shape such as bowl, crater precipice down to the central relief; volcanic acetabular as surrounded steep precipice. As follows: 

 Crater 

 Usually in the mountain crater Central, will be known as the main crater (Main crater), formed in the side of a volcano crater called the Deputy (Pareasitic crater), a result of a volcanic eruption in the number of different locations each exhaled not identical, it is often a volcanic crater several months. Peltate in Hawaii volcano, there are many Xiaowa pool crater called Point (Volcanic sinks), this crater is mainly low-chu from the underground magma caused the collapse, it is the fall of the crater. If a volcano crater in another form, called the nest-shaped crater (Nested crater), this crater is the first generation to generation in a volcanic eruption in the mouth, so that the expansion of the original crater, and in the old fire Yamaguchi caused new crater and volcanic cone, and then on another part of continue to form a nest-shaped. Nest-shaped volcanoes and volcanic parasitic different, if the body in a volcanic cone that is the side of the slope have volcanic eruptions, the formation of a new volcanic body, then this new body is parasitic volcano volcano; for example, on Yangmingshan Mountain Shamao Tatun Mountain is a parasitic volcano, and the nest-shaped volcano in the re-eruption of the crater formed.

Volcanic acetabular 

 Acetabular past volcanic formation, is generally believed that due to the role of violent volcanic eruptions formed, but now that its main reason for the fall. William's view that some pot-shaped crater is separate from the role of the formation of the outbreak, although it said this little pot-shaped crater, the percent of area is also small. Regardless of the shape of a volcano, the first generation to start by the eruption of the role, but due to the bottom of a large number of cone after the eruption, leading to the bottom of emptiness, causing cone roof fall, forcing extended crater, which had been preceded by a number of volcanic acetabular by the eruption, after the fall into the dual role, Kirton also think that Williams and 10000 Milan (Vam Bemmelan) and others advocated by the fall of pot-shaped crater that should be called the outbreak of the fall, said (Explosion-collapse theory) a small number of volcanic acetabular? role may be purely made before or at the same time, there is no role with see eruption. Large volcanic depression, such as the Hawaiian Islands on crater and the crater are purely as a result of magma column lower down, causing the fall from the upper, resulting crater around often associated fault precipice gradually so that the expansion of the volcanic crater cave wall to form a large pot-shaped crater. fire in the pot-shaped mouth, there is a special form for the pot-shaped settlement (Cauldron subsidence). If a nearly circular block, subsidence in the lava cave in, so that by the extrusion of magma along the vertical cracks increased, resulting in ring-dyke, so in the pot-shaped crater area can be found to be corroded ring dyke with the same structure exists. 

 Volcano tectonic depression 

 Emitted by a volcanic eruption of pumice and lava material for the volume of a great accumulation of these substances in the surrounding volcanic and increase the pressure formation in the region, and the formation because of the large number of magma beneath the smoke, after this pressure was more prone to faults or folds fall, caused by depression. Indonesia's Sumatra island has a low-lying land, William style that is because a large number of pumice smoke caused by the formation of large-scale fall into, one of them? Stubble j flurried the pools of stagnant water to form the Palestinian territories Lake (Lake Toba). In the volcanic cone on the slopes, often many deep depressions, known as the Graben area (Sector Grabens), presumably because of the underground magma is empty, causing the top block down from faulting occurred, because faulting regard to the flank the movement of a larger formation of wide groove, then known as the volcanic groove (Volcanic rents). 

 

 The volcanic plateau and the plains 

 If the volcanic eruption in the region will have become flat lava plains (Lava plains), the majority of the lava plateau and plain, are all composed of mafic lava, only Yellowstone plateau and Ignatius plateau of lava and volcanic-rich acidic tuff. If the lava from a central volcano eruption outward flow, then it should by into cone and cereal-like lava flows, it is not easy sharing into a large, this lava outflows should be very calm along the spillover from many cracks before they can piled up into a plain or plateau. a region that volcanic eruptions can cause plain or plateau, depending on the volcanic cracks be persistent, if the rock cracks in the open ductus straight, then the person into a cone or volcanic fornix; if the closure of the old sewing sewing again opened a new, long-term outflow of lava pulp but not the accumulation of the same ground, then by becoming lava plateau or plateau; a wide range of lava plateau requires a large amount of cracks can only be formed, and the shield-shaped volcano (Shield volcano) the generation, you do not need so many crater.

Associated volcanic phenomena

Lava 

 Volcanic eruptions, and many hot substances resulting debris thrown out, depending on size, including wood block Hill (Blocks), volcanic bombs (Bombs), volcanic ash (Scoriae), lapilli (Lapilli), ash ( Volcanic ash) volcanic dust (Volcanic dust) and so on, these hot debris substances by the hard rock is not formed by fragmentation, many of which are from melting? Lok hemorrhoids Qiao steamed cavity marks stumble grass mountain peak by Cheng Tao t Solidification , hot debris objects on the surface after the precipitation, with the nature of easy infiltration of water, so the front springs may have exposed. Volcano lava according to relief and downward mobility, with the flow with the condensate, the solidification of the form, there are two: 

 I. rope lava layer (Pahoehoe or Dermolithic soildofocation) ︰ lava when condensation swift into a rope to each other, or according to the terrain so steep hanging carpet-like (Tapestry), the surface of folds, not yet solidified ago, contains large quantities of gas outward proliferation, Therefore, some people refer to live lava (Live lava). 

 II. Blocky lava layer (Aa or Clastolithic solidification): This multi-surface lava rock ember iron surface into jagged lava gas has already escaped, only by air during filling. On top of the volcanic lava flows, but also generate some small terrain, may be as follows: 

 Convex dome (Tumuli) ︰ lava lava flows to the bottom of a large number of the collision, so that the role of the lava dome shell occurred, lava flow surface uplift, and its shape much like magma generated in the level of the rock strata under the condensation plate (Laccoli-ths). 

 Squeeze Hill (Squeeze-ups) ︰ have since been solidified lava viscosity of the lava crust fragments emitted Department to form a hill, called the extrusion Hill. Qiu greater volume extrusion special called pressure ridges (Pressure ridges). These pressures from cross-section of the ridge can be seen on both sides are very steep, and if the plane Anticline, chiropractors Top squeezing can break down, the pressure ridge line with regular and parallel flow of lava flows, and they When the formation of cumulus extrusion line from the horizontal pressure on the horizontal side of the source of the pressure has not yet really knows. 

 Lava bubbles (Lavablisters) ︰ lava contains large quantities of gas, lava eruption immediately after the solidification, the gas has not been fully escape, in the lava layer uplift in a big bubble. 

 Lava lava cave and tunnel (Lava tunnels) ︰ quality in the basalt lava area, if solidified lava in the shell under the water too often can be eroded into a lava tunnel, and if the erosion of the land can not cross, then the into the tunnel but not lava cave (Lava caves). This lava cave in winter into ice water may be to warm summer weather in the outside world, however difficult and lava cave in the cold phase replacement, although it is to summer, ice hole still exists, says the ice cave (Ice caves). 

 Ash Array 

 By Vulcan and even the skin's volcanic eruption of material from a large number of volcanic ash, known as gray array (Ash showers), gray patches are smaller and can be landed in the distance from the crater area. 1886 New Zealand Tarawera ash array in the crater with a radius of 30 miles of the landing by volcanic pumice stone tablets (Pumiceous lapilli), while 30 miles away from the colony who do it be? Po s gray . Ash array on the ground after landing, ground to cover up the original, but the original large undulating terrain still looming; volcanic eruptions were generally more porous layer of condensation, easy to water, it is not easy in the development of its rivers, but volcanic ash small array of material, water is not easy in the thin surface of the water system can be formed, often can be washed into the evil of its terrain. 

 Lahar 

 Volcanic eruptions often mudslides (Mud flow) associated. The occurrence of lahar, mainly because: 

 When the eruption of volcanic ash on the ground and landed in the snow to melt snow and ice, its ash, accompanied by melt water mudflows. 

 Lianyun sediment in the skin occurred on heavy rain washed mud flow could be into. 

 Lianyun river sediment and leather mixed mudflows. 

 Fire lake dried up, the bottom ash deposition, erosion by water into a mud flow. 

 Lahar substances in boulders and fine soil, mixed deposition, there is no level, multi-surface uplift hill, there are categories of landslides accumulation, mud flows fluency slopes up to dozens of kilometers, and can be submerged villages and small farms . 

 Embolization fornix 

 If the volcanic eruption, many of which are precursors of acid andesite lava, with even big sticky, then when it is difficult to drain out when the eruption, and in the crater ring do not pile up or the surface of the rock uplift into a dome, the arch terrain dome called embolization, or volcanic Suppository (Plug domes). If the bulge at the top of the dome-shaped type of bacteria, known as the dome-shaped plot (Cumulo-domes or tholoids). General? Yue Xiu b Multi-Burner into cylindrical. Embolization fornix and volcanic neck (Volcanic neck) is different because the former is from the magma into the volcano crater or red to the accumulation of condensation from above, so when it is generated at the beginning of the fait accompli uplift, and volcanic neck is the first in the dark volcanic condensate from the vertical gap, after a long-term weathering erosion, the exposed surface before.

The form of volcanic eruption

1908 A. Lacroix According to the volcanic eruption of the way volcanic divided into the following categories:



HI-style (Hawaiian phase) of this volcanic eruptions were a large number of mafic lava flows, the bursting of the activities of smaller outflow of lava from the crater, along the volcanic slopes cracks down slow flow, the formation of volcanic ash. In 1942 at the end of the HI(Mauna Loa) volcanic eruption of such volcanic examples. According to McDonald (GA Macdonald) a description of the eruption of the volcano, is divided into three phases:

Emitting hot lava period: the first phase, a total of continuing a few hours, the formation of thin-layer accumulation of lava flows of lava flows or hilly.

History of red packets even type (Strombolian phase) north of Sicily have Lai Pali Islands, the history of our fire red packets (Strombo-li) for one of the island group of volcanoes; this type of volcanic eruption has not stopped ever since, emitted by the base of the lava flow less acidic substances more debris in the air to form cloud of black smoke due to frequent hot flame smoke, the volcano known as sea lighthouse.

V-type (Vulcanian phase) also volcanic islands, but the way it erupted again and the history of volcanic force Chong package is different from the eruption of the material-rich stickiness Once exposed to air, easy to condenses into solid, so between the two eruptions, emitting lava has condenses into hard-shell, once again when the second eruption of lava cemented shell Chong split into pieces, a large number of volcanic ash with a large number of gas up out in the air the formation of a black cloud cauliflower, this cloud of darkness very easy to darkness, said the cloud of material has not been white-hot, so the lack of light.

Even skin type (Neuees Ardentes) of this type is more violent eruption, the most thick clouds of smoke, the largest eruption of viscous material, a very fine hot ash and thick rock debris, mixed with hot gases, a synthetic milk -like substances, heavy red upward to become white-hot light of the cloud, that is well-known skin Lianyun, also known as the volcanic cloud. Clouds unstable material, adhesive is also large, wait until the accumulation of thicker, the buoyancy?  Luo H continue to support their floating in the air, coupled with the role of gravity, are based on great speed crashed down any biological hit will be the death of .

Lava flooding period: the current population is still coming volcanic lava outflow, so that the lava continued thickening layer and hilly.

Jet period: the current volcano has become a spent force, only the gas appears, quantity also slowed down sharply.

The distribution of the world's volcanoes

The distribution of the world's volcanoes 

 Volcanic type 

 Volcanic general classification can be divided into: 

 Active volcanoes (Active volcanoes): activities are still from time to time 

 Dormant volcano (Dormant volcanoes): now has stopped, but the lack of change in erosion 

 Extinct (Extinct volcanoes) in the history of mankind there is no activity recorded, nor signs of activity 

 But can the awakening of a dormant volcano, extinct volcanoes can be resurrected, so as only the records of the past to distinguish it, may not be quite correct. 

 Volcano Distribution 

 The world's leading volcanic belt, the Department of the distribution around the edge of the Pacific, known as the "ring of fire" (Ring of Fire), accrued from the Chilean Andes in South America, the north by Peru, Central America, Mexico, the United States west card Mountains (Cascade range), north-west trip to the Aleutian Islands, Kamchatka, Kuril Islands, Japan, Okinawa, Taiwan, the Philippines, Celebes, New Guinea, Solomon Islands (Solomon Is.), New Caledonia Anthony (New Caledonia), and New Zealand. This is a ring of fire in general and the Pacific Rim of the seismic zone is consistent with what might be called seismicity (Mobile Belt of Earth Crust). In addition to that one of the main volcanic zone, there are other six areas: 

 Pacific Islands District ︰ including the Hawaiian Islands, and the Galapagos Islands off the coast of South America (Galapagos Is. Are Ecuador), Jurassic TU charges Nandi from the island (Juan Fernandez Isles, the case of Chile). 

 Nanyang ︰ equatorial zones, including Timor, Java, Bali and Sumatra islands. 

 India ︰ the west side of the Arab region, Madagascar Island and the East African Rift Valley Volcanoes. 

 ︰ Mediterranean from Turkey with a very East  (Mt.Ararat) from Italy to the west by the Atlantic Ocean, the Azores, Canary Is. And so on. 

 Volcanoes of the West Indies. 

 Iceland and the Faroe Islands and other isolated areas.

The causes of volcanic formation

Volcano (Volcano) from the Italian term "Vulcano", was Italy in the Mediterranean Lipari Islands (Lipari Islands) the name of a volcano, and later became a synonym volcano. Vulcan in ancient Rome and the middle finger text 』『 Vulcan. 

 Volcanic movements and the Earth's interior melt the liquid, the drive is closely related to the plate movement. 

 Plate movement 

 Earth's surface and shallow parts can be divided into a number of large plates. Plate, including the crust and upper mantle, which is equivalent to the lithosphere, about 100 kilometers thick. Cubicles each plate boundary in its relative movement to do: First, the expansion of (Divergence), First subduction (Convergence); This is the plate movement. Volcanic activity generally occurs in places where the transfer plate or in the vicinity, mainly divided into three parts: 

 Plate expansion zones: the Pacific ridge belt, the Atlantic Ocean and the Indian Ocean ridge with mid-ocean ridge volcanic belt are here. 

 Plate subduction zone: circum-Pacific belt and the Mediterranean volcanic belt occurred in the vicinity. 

 Hot spots: located in the upper mantle in the magma may be generated when the plates so the level of movement, after the volcanic hot spot will be generated, this will cause a succession of a series of volcanoes, and volcanic generated farther away from the hot spots are getting old. Islands such as Hawaii volcano. 

 And plate movement makes magma generate and increase in the ground caused by volcanic outflow. 

 Magma generation and outflow 

 Refers to the volcanic activity deep underground magma flow to the ground phenomenon. And all we can see the volcanic activity, but from the beginning of magma into the ground to stop the activities during this period of the phenomena it. The activities carried out under the ground must use other methods to speculate. The following is a magma underground activities: 

 Magma generated places: the majority of magma generated in the lower crust to between the upper mantle (about 20-200 km Inter), but more in the upper mantle. 

 Magma generated conditions: the Earth's interior temperature distribution in the ground temperature of 200 kilometers, it is estimated that in 1200 ℃ to 1600 ℃ around. In this temperature, the department's ultrabasic silicate minerals most of which do not melt. Because if the melting, the temperature must increase, otherwise the melting point of silicate minerals will be reduced. Magma generated by the reasons therefore are: the temperature increased, the water content increased, the pressure to reduce such. Temperature increased the way: The letter of thermal convection, in part, the letter can temperature; some stress due in part to strengthen the letter of the temperature. Pressure mantle silicate minerals will reduce the melting point lower mantle within the water will also increase the melting point of silicate minerals, such as lower. Earth around the magma generated is not the same as the reasons, that is, around the magma generation mechanism. Under the magma ocean ridges, the magma under the continental margin, island arc magma and the mainland under the magma, and its formation mechanism are different from each other. 

 Rise with the composition of magma changes: magma pressure inside the shelters if more than the pressure of rock, the magma on the rise along the cracks to the ground. Magma on the rise during the period, with the temperature and pressure of the lower part of the beginning of the crystallization of minerals, but also began to change in composition of magma. The results of flow to the ground, it generated a variety of igneous rock. For the rising magma mechanism and composition changes (differentiation) is also a variety of views, such as rising magma generated directly to the surface,? Beckmannia b rise during the magma composition of some change, some will not change; magma (original magma) began to rise after generation, but in mid-stay for some time (the formation of the so-called magma library, Magma reservoir) after rising to the surface, in such cases, the magma composition in the original magma rising in the magma library or second rise are likely to change. As the number of magma stay? M component change can do a variety of places to consider.

Antarctica also volcano!

In the West Antarctic ice sheets (West Antarctic ice sheet, WAIS), the found in 2300 before the eruption of the volcano.


In fact, as early as 1993, Donald Blankenship of the University of Texas and others, on the use of geophysical methods have been found in the West Antarctic ice sheet under the active volcano in the activities, the most recent eruption was in 7500 estimated that before. But this result has been no direct observational evidence.


Recently, British Antarctic Survey team, Hugh Corr and David Vaughan has used airborne radar (airbone radar) observation, the same in the West Antarctic ice sheet, the discovery of the volcanic eruption may be formed by volcanic ash strata, it is estimated that the eruption was in 2300 before.



Even if the volcanic eruption is likely to melt ice sheets, but, based on calculations, each cubic meters of magma, a maximum of only 14 cubic meters of ice melting. According to estimates by radar signal reflection, more than 2000 years ago, the eruption of the volcanic eruption volume, only about 0.019 to 0.31 cubic kilometers fell between the middle-scale volcanic eruption.


Although the ice has been melting away little but ash and pyroclastic spread air or through the ice, a broad distribution of a considerable area. Far from over a thousand kilometers away Bingxin (ice core) sampling, are also clearly found that a layer of volcanic ash heap of records in the ice.


It now appears that the Antarctic under the volcanic eruptions, has become the melting ice, rising sea-surface one of the killers!