SuperVulkano Activity Word 5/november/2013 ➭ ............................................ Tuesday, 5th November 2013 :: 21:06:52 UTC 1)Supervolcanoes Activity Report VEI Index: 8 Name: High Island Volcano ID: Country: China Location: Hong Kong Diameter: 6 km³ Last Eruption: ~140 million years ago Some 140 million years after it erupted and then toppled into the sea, an ancient super volcano in Hong Kong is making headlines. The newly-discovered High Island Super volcano spurted out 1,300 cubic kilometres of ash about 140 million years ago, enough to blanket all of Hong Kong. The super volcanic eruption on the southeastern China seaboard would have produced a global environmental impact and could be related to the extinction of dinosaurs, according to a handout from Hong Kong’s Geotechnical Engineering Office that conducted the research. hisz.rsoe.hu/alertmap/index2.php ____________________________________ 2) Supervolcanoes Activity Report VEI Index: 8 Name: Island Park Caldera Volcano ID: 1205-01- Country: Unites States of America Location: State of Idaho Diameter: 2,500 km³ Last Eruption: 2.1 million years ago The volcanic feature commonly called the Island Park Caldera in the state of Idaho, USA, is actually two calderas, one nested inside the other. The Island Park Caldera is the older and much larger caldera, with approximate dimensions of 58 miles (93 km) by 40 miles (64 km). Its ashfall is the source of the Huckleberry Ridge Tuff that is found from southern California to the Mississippi River near St. Louis. This supereruption (2500 cubic kilometers) occurred 2.1 million years BP and produced 2,500 times as much ash as the 1980 Mount St. Helens eruption. The caldera clearly visible today is the later Henrys Fork Caldera that is the source of the Mesa Falls Tuff. It was formed in an eruption of more than 280 cubic kilometers 1.3 million years BP. The two nested calderas share the same rim on their western sides, but the older Island Park Caldera is much larger and more oval and extends well into Yellowstone Park. The Island Park Caldera is sometimes referred to as the First Phase Yellowstone Caldera or the Huckleberry Ridge Caldera. To the southwest of the caldera lies the Snake River Plain, which was formed by a succession of older calderas marking the path of the Yellowstone hotspot. The Plain is a depression, sinking under the weight of the volcanic rocks that formed it, through which the Snake River winds. Other observable volcanic features in the Plain include: the Menan Buttes, the Big Southern Butte, Craters of the Moon, the Wapi Lava Field and Hells Half Acre. These calderas are in an area called Island Park that is known for beautiful forests, large springs, clear streams, waterfalls, lakes, ponds, marshes, wildlife, and fishing. Harriman State Park is located in the caldera. Snowmobiling, fishing, and Nordic skiing, and wildlife viewing are popular activities in the area. The peaks of the Grand Tetons to the southeast are visible from places in the caldera. hisz.rsoe.hu/alertmap/index2.php _________________________________ 3) Supervolcanoes Activity Report VEI Index: 8 Name: La Garita Caldera Volcano ID: 000 Country: Unites States of America Location: State of Colorado Diameter: ~5,000 km³ Last Eruption: ~27.8 million years ago La Garita Caldera is a large volcanic caldera located in the San Juan volcanic field in the San Juan Mountains in southwestern Colorado, United States, to the west of the town of La Garita, Colorado. The eruption that created the La Garita Caldera was, perhaps, the largest known explosive eruption in all of Earths history (the Siberian Traps may have been larger but the cause is still being debated). The La Garita Caldera is one of a number of calderas that formed during a massive ignimbrite flare-up in Colorado, Utah and Nevada from 40–25 million years ago, and was the site of truly enormous eruptions about 28–26 million years ago, during the Oligocene Epoch. The area devastated by the La Garita eruption is thought to have covered a significant portion of what is now Colorado, and ash could have fallen as far as the east coast of North America and the Caribbean. The scale of La Garita volcanism was far beyond anything known in human history. The resulting deposit, known as the Fish Canyon Tuff, has a volume of approximately 1,200 cubic miles (5,000 km3), enough material to fill Lake Michigan (in comparison, the May 18, 1980 eruption of Mt. St. Helens was only 0.25 cubic miles (1.0 km3) in volume). By contrast, the most powerful human-made explosive device ever detonated, the Tsar Bomba or Emperor Bomb, had a yield of 50 megatons, whereas the eruption at La Garita was approximately 105 times more powerful. It is possibly the most energetic event on Earth since the Chicxulub impact, which was 50 times more powerful. hisz.rsoe.hu/alertmap/index2.php ____________________________________ 4) Supervolcanoes Activity Report VEI Index: 8 Name: Lake Taupo Volcano ID: 0401-07= Country: New Zealand Location: North Island Diameter: ~616 km³ Last Eruption: ~26,500 years ago Lake Taupo is a lake situated in the North Island of New Zealand. With a surface area of 616 square kilometres (238 sq mi), it is the largest lake by surface area in New Zealand, and the largest freshwater lake by surface area in Oceania. Lake Taupo has a perimeter of approximately 193 kilometres, a deepest point of 186 metres. It is drained by the Waikato River (New Zealands longest river), while its main tributaries are the Waitahanui River, the Tongariro River, and the Tauranga-Taupo River. It is a noted trout fishery with stocks of introduced brown trout and rainbow trout. The lake lies in a caldera created following a huge volcanic eruption (see supervolcano) approximately 26,500 years ago. According to geological records, the volcano has erupted 28 times in the last 27,000 years. It has predominantly erupted rhyolitic lava although Mount Tauhara formed from dacitic lava. The largest eruption, known as the Oruanui eruption, ejected an estimated 1,170 cubic kilometres of material and caused several hundred square kilometres of surrounding land to collapse and form the caldera. The caldera later filled with water, eventually overflowing to cause a huge outwash flood. Several later eruptions occurred over the millennia before the most recent major eruption, which occurred in 180 CE. Known as the Hatepe eruption, it is believed to have ejected 100 cubic kilometres of material, of which 30 cubic kilometres was ejected in the space of a few minutes. This was one of the most violent eruptions in the last 5,000 years (alongside the Tianchi eruption of Baekdu at around 1000 and the 1815 eruption of Tambora), with a Volcanic Explosivity Index rating of 7. The eruption column was twice as high as the eruption column from Mount St. Helens in 1980, and the ash turned the sky red over Rome and China. The eruption devastated much of the North Island and further expanded the lake. The area was uninhabited by humans at the time of the eruption, since New Zealand was not settled by the Maori until several centuries later at the earliest. Taupos last known eruption occurred around 210 CE, with lava dome extrusion forming the Horomatangi Reefs, but that eruption was much smaller than the 11z0 CE eruption. The 180 eruption was one of the largest in recorded history. The skies and sunsets formed from this eruption were noted by Roman and Chinese observers. Any possible climatic effects of the eruption would have been concentrated on the southern hemisphere due to the southerly position of Lake Taupo. Underwater hydrothermal activity continues near the Horomatangi vent, and the volcano is currently considered to be dormant rather than extinct. hisz.rsoe.hu/alertmap/index2.php ___________________________________ 5) Supervolcanoes Activity Report VEI Index: 8 Name: Lake Toba Volcano ID: 0601-09= Country: Indonesia Location: Northern Sumatra Diameter: ~2,800 km³ Last Eruption: ~74,000 years ago Lake Toba (Indonesian: Danau Toba) is a lake and supervolcano, 100 kilometres long and 30 kilometres wide, and 505 metres (1,666 ft) at its deepest point. Located in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 metres (2,953 ft), the lake stretches from 2°53N 98°31E / -2.88°N. It is the largest volcanic lake in the world. In addition, it is the site of a supervolcanic eruption that occurred about 74,000 years ago,[2] a massive climate-changing event. The eruption is believed to have had a VEI intensity of 8. This eruption is believed to have been the largest anywhere on Earth in the last 25 million years. According to the Toba catastrophe theory to which some anthropologists and archeologists subscribe, it had global consequences, killing most humans then alive and creating a population bottleneck in Central Eastern Africa and India that affected the genetic inheritance of all humans today. The Toba eruption (the Toba event) occurred at what is now Lake Toba about 67,500 to 75,500 years ago. The Toba eruption was the latest of a series of at least three caldera-forming eruptions which have occurred at the volcano, with earlier calderas having formed around 700,000 and 840,000 years ago. The last eruption had an estimated Volcanic Explosivity Index of 8 (described as mega-colossal), making it possibly the largest explosive volcanic eruption within the last twenty-five million years. Bill Rose and Craig Chesner of Michigan Technological University have deduced that the total amount of erupted material was about 2,800 km3 (670 cu mi) — around 2,000 km3 (480 cu mi) of ignimbrite that flowed over the ground, and around 800 km3 (190 cu mi) that fell as ash, with the wind blowing most of it to the west. The pyroclastic flows of the eruption destroyed an area of 20,000 square kilometres (7,722 sq mi), with ash deposits as thick as 600 metres (1,969 ft) by the main vent. To give an idea of its magnitude, consider that although the eruption took place in Indonesia, it deposited an ash layer approximately 15 centimetres thick over the entire Indian subcontinent; at one site in central India, the Toba ash layer today is up to 6 metres thick[9] and parts of Malaysia were covered with 9 m of ashfall.[10] In addition it has been calculated that 1010 metric tons of sulphuric acid[citation needed]was ejected into the atmosphere by the event, causing acid rain fallout. The Toba caldera is the only supervolcano in existence that can be described as Yellowstones bigger sister. With 2,800 km3 of ejecta, it was an even greater eruption than the supereruption (2,500 km3) of 2.1 million years ago that created the Island Park Caldera in Idaho, USA. The eruption was also about three times the size of the latest Yellowstone eruption of Lava Creek 630,000 years ago. For further comparison, the largest volcanic eruption in historic times, in 1815 at Mount Tambora (Indonesia), ejected the equivalent of around 100 km3 (24 cu mi) of dense rock and made 1816 the Year Without a Summer in the whole northern hemisphere, whilst the 1980 eruption of Mount St. Helens in Washington State ejected around 1.2 km3 (0.29 cu mi) of material. The subsequent collapse formed a caldera that, after filling with water, created Lake Toba. The island in the center of the lake is formed by a resurgent dome. Landsat photo of Sumatra surrounding Lake Toba. Though the year may never be precisely determined, the season can: only the summer monsoon could have deposited Toba ashfall in the South China Sea, implying that the eruption took place sometime during the northern summer.[12] The eruption lasted perhaps two weeks, but the ensuing volcanic winter resulted in a decrease in average global temperatures by 3 to 3.5 degrees Celsius for several years. Greenland ice cores record a pulse of starkly reduced levels of organic carbon sequestration. Very few plants or animals in southeast Asia would have survived, and it is possible that the eruption caused a planet-wide die-off. There is some evidence, based on mitochondrial DNA, that the human race may have passed through a genetic bottleneck around this time, reducing genetic diversity below what would be expected from the age of the species. According to the Toba catastrophe theory proposed by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign in 1998, human populations may have been reduced to only a few tens of thousands of individuals by the Toba eruption. Smaller eruptions have occurred at Toba since. The small cone of Pusukbukit has formed on the southwestern margin of the caldera and lava domes. The most recent eruption may have been at Tandukbenua on the northwestern caldera edge, since the present lack of vegetation could be due to an eruption within the last few hundred years. Some parts of the caldera have experienced uplift due to partial refilling of the magma chamber, for example pushing Samosir Island and the Uluan Peninsula above the surface of the lake. The lake sediments on Samosir Island show that it has been uplifted by at least 450 metres[7] since the cataclysmic eruption. Such uplifts are common in very large calderas, apparently due to the upward pressure of unerupted magma. Toba is probably the largest resurgent caldera on Earth. Large earthquakes have occurred in the vicinity of the volcano more recently, notably in 1987 along the southern shore of the lake at a depth of 11 km.[15] Other earthquakes have occurred in the area in 1892, 1916, and 1920-1922. Lake Toba lies near the Great Sumatran fault which runs along the centre of Sumatra in the Sumatra Fracture Zone. The volcanoes of Sumatra and Java are part of the Sunda Arc, a result of the northeasterly movement of the Indo-Australian Plate which is sliding under the eastward-moving Eurasian Plate. The subduction zone in this area is very active: the seabed near the west coast of Sumatra has had several major earthquakes since 1995, including the 9.3 2004 Indian Ocean Earthquake and the 8.7 2005 Sumatra earthquake, the epicenters of which were around 300 km from Toba. On 12 September 2007, a magnitude 8.5 Earthquake shook the ground in Sumatra and was felt in the Indonesian capital, Jakarta. The epicenter for this earthquake was not as close as the previous two earthquakes, but it was in the same vicinity. Most of the people who live around Lake Toba are ethnically Bataks. Traditional Batak houses are noted for their distinctive roofs (which curve upwards at each end, as a boats hull does) and their colorful decor. hisz.rsoe.hu/alertmap/index2.php _________________________________ 6) Supervolcanoes Activity Report VEI Index: 8 Name: Yellowstone Caldera Volcano ID: 1205-01- Country: Unites States of America Location: State of Wyoming Diameter: 1,000 km³ Last Eruption: 640,000 years ago The Yellowstone Caldera is the volcanic caldera in Yellowstone National Park in the United States. The caldera is located in the northwest corner of Wyoming, in which the vast majority of the park is contained. The major features of the caldera measure about 55 kilometers (34 mi) by 72 kilometers (45 mi) as determined by geological field work conducted by Bob Christiansen of the United States Geological Survey in the 1960s and 1970s. After a BBC television science program coined the term supervolcano in 2000, it has often been referred to as the Yellowstone Supervolcano. Yellowstone, like Hawaii, is believed to lie on top of an area called a hotspot where light, hot, molten mantle rock rises towards the surface. While the Yellowstone hotspot is now under the Yellowstone Plateau, it previously helped create the eastern Snake River Plain (to the west of Yellowstone) through a series of huge volcanic eruptions. Although the hotspots apparent motion is to the east-northeast, the North American Plate is really moving west-southwest over the stationary hotspot deep underneath. Over the past 17 million years or so, this hotspot has generated a succession of violent eruptions and less violent floods of basaltic lava. Together these eruptions have helped create the eastern part of the Snake River Plain from a once-mountainous region. At least a dozen or so of these eruptions were so massive that they are classified as supereruptions. Volcanic eruptions sometimes empty their stores of magma so swiftly that they cause the overlying land to collapse into the emptied magma chamber, forming a geographic depression called a caldera. Calderas formed from explosive supereruptions can be as wide and deep as mid- to large-sized lakes and can be responsible for destroying broad swaths of mountain ranges. The oldest identified caldera remnant straddles the border near McDermitt, Nevada-Oregon. Progressively younger caldera remnants, most grouped in several overlapping volcanic fields, extend from the Nevada-Oregon border through the eastern Snake River Plain and terminate in the Yellowstone Plateau. One such caldera, the Bruneau-Jarbidge caldera in southern Idaho, was formed between 10 and 12 million years ago, and the event dropped ash to the depth of a foot 1,000 miles (1,600 km) away in northeastern Nebraska and killed a large herd of rhinoceroses, camels, and other animals at Ashfall Fossil Beds State Historical Park. Within the past 17 million years, 142 or more caldera-forming eruptions have occurred from the Yellowstone hotspot . The loosely defined term supervolcano has been used to describe volcanic fields that produce exceptionally large volcanic eruptions. Thus defined, the Yellowstone Supervolcano is the volcanic field which produced the latest three supereruptions from the Yellowstone hotspot. The three super eruptions occurred 2.1 million, 1.3 million, and 640,000 years ago; forming the Island Park Caldera, the Henrys Fork Caldera, and Yellowstone calderas, respectively. The Island Park Caldera supereruption (2.1 million years ago), which produced the Huckleberry Ridge Tuff, was the largest and produced 2,500 times as much ash as the 1980 Mount St. Helens eruption. The next biggest supereruption formed the Yellowstone Caldera (630,000 years ago) and produced the Lava Creek Tuff. The Henrys Fork Caldera (1.2 million years ago) produced the smaller Mesa Falls Tuff but is the only caldera from the SRP-Y hotspot that is plainly visible today. Non-explosive eruptions of lava and less-violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption. The most recent lava flow occurred about 70,000 years ago, while the largest violent eruption excavated the West Thumb of Lake Yellowstone around 150,000 years ago. Smaller steam explosions occur as well; an explosion 13,800 years ago left a 5 kilometer diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera). Currently, volcanic activity is exhibited via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser, plus recorded ground swelling indicating ongoing inflation of the underlying magma chamber. The volcanic eruptions, as well as the continuing geothermal activity, are a result of a great cove of magma located below the calderas surface. The magma in this cove contains gases that are kept dissolved only by the immense pressure that the magma is under. If the pressure is released to a sufficient degree by some geological shift, then some of the gases bubble out and cause the magma to expand. This can cause a runaway reaction. If the expansion results in further relief of pressure, for example, by blowing crust material off the top of the chamber, the result is a very big gas explosion. hisz.rsoe.hu/alertmap/index2.php _________________________________ 7) Supervolcanoes Activity Report VEI Index: 7 Name: Long Valley Caldera Volcano ID: 120314-A Country: Unites States of America Location: State of California Diameter: 600 km³ Last Eruption: ~760,000 years ago Long Valley Caldera is a depression in eastern California that is adjacent to Mammoth Mountain. The valley is one of the largest calderas on earth, measuring about 20 miles (32 km) long (east-west) and 11 miles (18 km) wide (north-south). The elevation of the floor of the caldera is 6,500 feet (2,000 m) in the east and 8,500 feet (2,600 m) in the west. The elevation of the caldera walls reach 9,800-11,500 feet (3,000-3,500 m) except in the east where the wall rises only 500 feet (150 m) to an elevation of 7,550 feet (2,300 m). Long Valley was formed 760,000 years ago when a huge volcanic eruption released very hot ash that later cooled to form the Bishop tuff that is common to the area. The eruption was so colossal that the magma chamber under the now destroyed volcano was significantly emptied to the point of collapse. The collapse itself caused an even larger secondary eruption of pyroclastic ash that burned and buried thousands of square miles. Ash from this eruption blanketed much of the western part of what is now the United States. Geologists call topographic depressions formed in this manner calderas. Subsequent eruptions from the Long Valley magma chamber were confined within the caldera with extrusions of relatively hot (crystal-free) rhyolite 700,000 to 600,000 years ago as the caldera floor was upwarped to form the resurgent dome followed by extrusions of cooler, crystal-rich moat rhyolite at 200,000-year intervals (500,000, 300,000, and 100,000 years ago) in clockwise succession around the resurgent dome. At its height 600,000 years ago, an Owens River-fed 300 foot (91 m) deep lake filled the caldera and rose to an elevation of 7,800 feet (2,400 m) above sea level. The lake was drained sometime in the last 100,000 years after it overtopped the southern rim of the caldera, eroded the sill and created the Owens River Gorge. A dam in the gorge has partially restored part of that lake which is now known as Lake Crowley. Since the great eruption many hot springs developed in the area and the resurgent dome has uplifted. During the last ice age, glaciers filled the canyons leading to Long Valley, but the valley floor was clear of ice. Excellent examples of terminal moraines can be seen at Long Valley: these moraines are the debris left from glacial sculpting. Laurel Creek, Convict Creek, and McGee Creek all have prominent moraines. In May of 1980, a strong earthquake swarm that included four Richter magnitude 6 earthquakes struck the southern margin of Long Valley Caldera associated with a 10 inch (25-cm), dome-shaped uplift of the caldera floor. These events marked the onset of the latest period of caldera unrest that continues to this day. This ongoing unrest includes recurring earthquake swarms and continued dome-shaped uplift of the central section of the caldera (the resurgent dome) accompanied by changes in thermal springs and gas emissions.[1] After the quake another road was created as an escape route. Its name at first was proposed as the Mammoth Escape Route but was changed to the Mammoth Scenic Loop after Mammoth area businesses and land owners complained. In 1982, the United States Geological Survey under the Volcano Hazards Program began an intensive effort to monitor and study geologic unrest in Long Valley Caldera. The goal of this effort is to provide residents and civil authorities in the area reliable information on the nature of the potential hazards posed by this unrest and timely warning of an impending volcanic eruption, should it develop.[1] Most, perhaps all, volcanic eruptions are preceded and accompanied by geophysical and geochemical changes in the volcanic system. Common precursory indicators of volcanic activity include increased seismicity, ground deformation, and variations in the nature and rate of gas emissions. hisz.rsoe.hu/alertmap/index2.php
Posted on: Tue, 05 Nov 2013 21:21:59 +0000
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