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Topic: Caldera Eruptions

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	USGS Photo Glossary: caldera
		The caldera is 10 km in diameter and 500-1,000 m deep.
		A caldera is a large, usually circular depression at the summit of a volcano formed when magma is withdrawn or erupted from a shallow underground magma reservoir.
		Calderas are different from craters, which are smaller, circular depressions created primarily by explosive excavation of rock during eruptions.
	volcanoes.usgs.gov /Products/Pglossary/caldera.html (340 words)

	blasts: University of Utah News Release: July 15, 2002
		The cataclysmic explosions - known as "caldera eruptions" - typically generated 250 to 600 times as much volcanic ash as the 1980 eruption of Mount St. Helens in Washington state, and some were up to 2,500 times larger, covering as much as half the continental United States with inches to feet of volcanic ash.
		But in a study of distinct volcanic ash layers deposited by each eruption, Perkins and Nash showed there were at least 142 catastrophic caldera eruptions during the past 16.5 million years, and at least four more in the preceding 500,000 years.
		Yellowstone hotspot caldera eruptions are believed to stem from molten basalt rising from depth, and then melting and mixing with the overlying granitic crust, which in turn erupts.
	www.utah.edu /unews/releases/02/jul/hotspot.html (1439 words)

	Global Volcanism Program \| Volcanoes of the World \| Types and Processes Gallery \| Calderas (Site not responding. Last check: 2007-10-25)
		Calderas are large volcanic depressions formed by collapse of the summit or flanks of a volcano into underlying chambers evacuated by very large explosive eruptions or the effusion of large volumes of lava flows.
		Calderas may be simple structures formed during an eruption that truncates either the summit of a single stratovolcano or a complex of multiple overlapping volcanoes, such as at Crater Lake in Oregon.
		Calderas are most often defined as depressions produced as a result of large-scale eruptions, but the word has also been used as a morphological term that encompasses volcanic depressions formed by erosion or large volcanic landslides.
	www.volcano.si.edu /world/tpgallery.cfm?category=Calderas (881 words)

	Tsunamis Generated by the Paroxysmal Eruptions, Explosions, Caldera Collapses and Slope Failures of the Krakatau ...
		The 1927 birth of Anak Krakatau volcano (Stern, 1929a) in the caldera of Krakatau altered significantly the underwater topography.
		This conclusion is supported by observations of the tsunami waves observed during the 1928 eruptions of Anak Krakatau the Son of Krakatau that subsequently formed in the area.
		It was this massive caldera collapse and the associated flank failures that generated the major catastrophic tsunami in the Sunda Strait.
	www.drgeorgepc.com /Tsunami1883Krakatau.html (6593 words)

	[No title]
		In contrast, the fissure eruption in 1938, which occurred to the north of the Grímsvötn caldera, melted 2 km³ of ice over several days as a subglacial hyaloclastite ridge with a volume of 0.3-0.5 km³ was formed.
		Comparison of the volume of ice melted during these caldera eruptions (0.02-0.05 km³) with that drained in typical jökulhlaups also suggests that their effect on the size and general behavior of the jökulhlaups is minor.
		This interaction of the caldera lake and the presumed shallow magma chamber in the crust is a feedback mechanism: The periodic variations in overburden pressure cause periodic tapping of the magma chamber.
	www.hi.is /~mmh/gos/a12.html (2911 words)

	CVO Website - Calderas and Caldera Formation
		Calderas at Yellowstone and Long Valley are associated with eruption of silicic magma as pyroclastic flows that covered large areas around and within the caldera.
		Yokoyama (1981, 1982) concluded that the caldera formed by explosive destruction and reaming of the preeruption edifice, and Camus and Vincent (1983) and Francis (1985) favored an origin by large-scale collapse of the northern part of Krakatau Island (similar to the volcanic landslide at Mount St. Helens on 18 May 1980).
		Long Valley caldera is located at the western edge of the Basin and Range Province straddling the eastern frontal fault escarpment of the Sierra Nevada, in which it forms a reentrant or offset commonly referred to as the "Mammoth embayment".
	vulcan.wr.usgs.gov /Glossary/Caldera/description_caldera.html (1943 words)

	Super Volcano Yellowstone
		The Oruanui eruption is thought to have formed the caldera now filled by Lake Taupo, but this large eruption also shows the influence of lake water in its fine grain size and abundant evidence for heavy rain during the eruption.
		Aira Caldera is a supervolcanic caldera in the south of the island of Kyushu, Japan.
		Eruptions of the Yellowstone volcanic system have included the two largest volcanic eruptions in North America in the past few million years; the third largest was at Long Valley in California and produced the Bishop ash bed.
	www.solcomhouse.com /yellowstone.htm (3670 words)

	Vic Camp - Calderas
		This caldera type is generated after the main phase of a Plinian eruption, during collapse of a stratovolcano into the void of the underlying, depleted magma chamber.
		Although the waning phase of a Plinian eruption is often associated with the generation of pyroclastic flows, piston-like collapse of the volcanic edifice can generate the additional eruption of voluminous, pumice-dominated sheet flows along ring fractures surrounding the collapsing mass.
		The caldera floor is typically filled with rhyolitic lavas, obsidian flows, and domes, and the uplifted centers often contain elongate rifts (graben) along their crests.
	www.geology.sdsu.edu /how_volcanoes_work/Calderas.html (991 words)

	Caldera. Photos and brief explanation
		The summit caldera of this large, explosive volcano that erupted last in 1728, is occupied by a glacier, which is part of the Vatnajökull ice cap that covers most of SE Iceland.
		Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif.
		The most recent of the Tengger calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the last ca.
	www.decadevolcano.net /photos/keywords/caldera.htm (842 words)

	Yellowstone Caldera Volcano 1
		Caldera complex volcanos are common on Earth, and the Valles caldera complex volcano clearly shows their typical history.
		Yellowstone caldera is two overlapping simultaneous caldera complex volcanos, with two distinct ring fractures and two separate resurgent domes.
		The following images of the geology of the Yellowstone caldera volcano are annotated onto the center of this frame.
	www.lpi.usra.edu /education/EPO/yellowstone2002/workshop/y_caldera1 (420 words)

	Rabaul Caldera, New Britain Island
		Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the northeast and western caldera walls.
		Phreatic eruptions occurred at Tavurvur in Feb. and March 1940, and intermittent explosive eruptions from June 1941 to April 1942 left a small crater on the floor of the larger 1937 crater.
		Almost all of the crater features produced by eruptions in 1878, 1937, 1941, and 1942 were destroyed and replaced by a single shallow bowl-shaped crater.
	users.bendnet.com /bjensen/volcano/swpacific/newbritain-rabaul.html (1210 words)

	Yellowstone Caldera
		Caldera eruptions on the Yellowstone scale have a world wide frequency of perhaps once every hundred thousand years.
		Eruptions that are separated by any significant period of time have discernible boundary effects that clearly separate one tuff from another.
		Near the northeast part of the caldera, seismic velocities are even lower to within about 2 miles of the surface; this may indicate a more continuous magma body that extends from the northeastern part of the caldera to about 10 miles beyond it.
	www.yellowstonenationalpark.com /calderas.htm (3218 words)

	Yellowstone National Park Caldera
		This eruption formed the Henrys Fork Caldera, located in the area of Island Park, west of Yellowstone National Park, and produced another widespread volcanic deposit called the Mesa Falls Tuff.
		Pyroclastic flows from this eruption left thick volcanic deposits known as the Lava Creek Tuff, which can be seen in the south-facing cliffs east of Madison, where they form the north wall of the caldera.
		Eruptions of rhyolite have been responsible for forming many of the world’s calderas, such as those at Katmai National Park, Alaska, which formed in an eruption in 1912, and at Long Valley, California.
	www.yellowstone.net /caldera.htm (495 words)

	Caldera Eruptions (Site not responding. Last check: 2007-10-25)
		Typical caldera forming eruptions occur in the late stages of stratovolcano evolution.
		The magnitude of the eruption is beyond the realm of imagination: 240 cubic miles of ash were blasted into the atmosphere, making this eruption perhaps the largest ever to occur on earth.
		After this eruption, the magma chamber collapsed into a gigantic pit reaching 28 by 47 miles (45 by 76 kilometers) across, and perhaps several thousand feet deep.
	www.indiana.edu /~geol105/images/gaia_chapter_5/caldera_eruptions.htm (235 words)

	Mount Mazama and Crater Lake: Growth and Destruction of a Cascades Volcano (Site not responding. Last check: 2007-10-25)
		The cataclysmic eruption of Mount Mazama 7,700 years ago started from a single vent on the northeast side of the volcano as a towering column of pumice and ash that reached some 30 miles (50 km) high.
		Eruptions of ash and pumice: The cataclysmic eruption started from a vent on the northeast side of the volcano as a towering column of ash, with pyroclastic flows spreading to the northeast.
		An eruption similar to the one 7,700 years ago is unlikely because large volumes of magma are not available to cause such an eruption.
	pubs.usgs.gov /fs/2002/fs092-02 (2297 words)

	Newswise
		The cataclysmic explosions -- known as "caldera eruptions" -- typically generated 250 to 600 times as much volcanic ash as the 1980 eruption of Mount St. Helens in Washington state, and some were up to 2,500 times larger, covering as much as half the continental United States with inches to feet of volcanic ash.
		They are the most devastating but most rare type of eruption.
		The Yellowstone hotspot -- which many scientists believe is a plume-like zone of hot and molten rising from at least 125 miles beneath Earth's surface -- produced its three most recent caldera eruptions at or near the present site of Yellowstone National Park 2 million, 1.3 million and 642,000 years ago.
	www.newswise.com /articles/view/?id=HOTSPOT.UUT (1416 words)

	Steam Explosions, Quakes, and Volcanic Eruptions—What’s in Yellowstone’s Future? \| USGS Fact Sheet ...
		Cataclysmic eruptions in the past few million years created huge volcanic depressions called “calderas.” The youngest, the Yellowstone Caldera, was formed 640,000 years ago.
		Within the caldera, rivers and streams commonly occupy the gaps between individual lava flows, and springs emerge at the edges of flows.
		Explosive eruptions are best compared by recalculating the volume of erupted volcanic ash and pumice (see photos) in terms of the original volume of molten rock (magma) released (shown in this diagram by orange spheres).
	pubs.usgs.gov /fs/2005/3024 (3852 words)

	Volcanoes of the Eastern Sierra Nevada
		The studies of Hildreth and Mahood (1986) indicate that the eruption of the Bishop Tuff followed a pattern common to caldera-forming eruptions, transitioning from a single vent, Plinian eruption phase (that may or may not include associated ashflows fed by the caldera collapse) to a ring-vent phase that later results in the caldera subsidence.
		The collapse of the caldera was followed by an almost immediate renewal of volcanic activity that constitutes the fourth phase (750-100 Ka) of volcanism in the Long Valley region.
		Bailey (1976) suggests that the three discrete locations of these eruptions are controlled by the intersection of major northwest-trending precaldera faults and the ring fracture zone the bound the resurgent dome.
	www.indiana.edu /~sierra/papers/2005/smith.html (4077 words)

	ScienceDaily: Mega Eruption Of Yellowstone's Southern Twin
		Eruptions at 2.0, 1.3, and 0.6 million years ago ejected huge volumes of rhyolite magma, and each formed a caldera and extensive layers of thick pyroclastic flow deposits," said Soler.
		The Vilama Caldera appears to have been created when the 10 by 24-mile roof catastrophically collapsed on a chamber of molten rock, or magma, explosively venting vast amounts of ignimbrites out in various directions.
		The trigger for the Vilama mega-eruption, says Soler, was probably the same thing that gave the caldera its football-like shape: The tectonic faults in the roof of the magma chamber which probably formed as a consequence of its own instability and/or from the significant stresses in the crust in that area.
	www.sciencedaily.com /releases/2006/03/060328183109.htm (1773 words)

	Global Volcanism Program \| Coatepeque Caldera \| Summary (Site not responding. Last check: 2007-10-25)
		The 7 x 10 km Coatepeque caldera, its eastern side filled by a caldera lake, was formed by collapse of a group of stratovolcanoes immediately east of Santa Ana volcano.
		The caldera was formed during a series of major rhyolitic explosive eruptions between about 72,000 and 57,000 years ago.
		Post-caldera eruptions included the formation of basaltic cinder cones and lava flows near the western margin of the caldera and the extrusion of a half dozen rhyodacitic lava domes along a NE-SW line near the caldera lake margins.
	www.volcano.si.edu /world/volcano.cfm?vnum=1403-041 (207 words)

	[No title]
		The Valles Caldera lies within the Jemez Volcanic Field, a large complex of basaltic through rhyolitic volcanism accumulated over the last 13 million years, culminating in ash flow eruptions and caldera collapse.
		The Valles Caldera is the type area for resurgent ash flow calderas.
		This type of caldera is characterized by post-collapse upward buldging, or resurgence, of the caldera floor and eruptions of late silicic domes along the interior ring fracture.
	www.nmmnh-abq.mus.nm.us /nmmnh/volcanoes/Jemez.html (485 words)

	Alaska Volcano Observatory - Staff (Site not responding. Last check: 2007-10-25)
		The most recent eruption at Aniakchak occurred in 1931 and was one of the largest explosive eruptions in Alaska in the last 100 years.
		Historical eruptions of Iliamna Volcano have not been positively documented; however, the volcano regularly emits steam and gas, and small, shallow earthquakes are often detected beneath the summit area.
		Prehistoric eruptions have generated plumes of volcanic ash, pyroclastic flows, and lahars that extended to the volcano flanks and beyond.
	www.avo.alaska.edu /about/staff.php?dirid=18 (6562 words)

	Rabaul Caldera, Papua New Guinea
		The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994.
		The eruptions declined in strength, and by Oct. 2, Vulcan was no longer erupting; Tavurvur continued throughout October and November.
		Despite the great danger of this eruption, only five people died; four from collapses of roofs, and one person was struck by lightning.
	volcano.und.nodak.edu /vwdocs/current_volcs/rabaul/rabaul.html (789 words)

	ScienceDaily: More Blasts From Yellowstone's Past: Hotspot Generated 142 Huge Eruptions, 40 Percent More Than ...
		Tiny Crystals Predict A Huge Volcano In Western United States (July 23, 2001) -- Reading the geochemical fine print found in tiny crystals of the minerals zircon and quartz, scientists are forming a new picture of the life history - and a geologic timetable - of a type of volcano...
		Mega Eruption Of Yellowstone's Southern Twin (March 28, 2006) -- North America isn't the only continent that's experienced super-colossal volcanic eruptions in the recent geologic past.
		The actual explosivity of these eruptions varies, but the sheer volume of extruded magma...
	www.sciencedaily.com /releases/2002/07/020716081303.htm (2765 words)

	Yellowstone Dominates North American Landscape With 142 Massive
		The hotspot, which powers the geysers and hot springs of Yellowstone has produced over 142 massive volcanic eruptions during the past 16.5 million years -- far more than the 100 previously known blasts, University of Utah geologists found.
		The study was originally published in the March 2002 issue of Geological Society of America Bulletin.
		The 142 eruptions were clustered in six or seven volcanic fields or "centers" extending from the Oregon-Idaho- Nevada border northeast to Yellowstone.
	www.spacedaily.com /news/tectonics-02h.html (1487 words)

	Yellowstone More Volcanically Active than Previously Estimated (Site not responding. Last check: 2007-10-25)
		It would be fascinating to see the next eruption, but not any fun to attempt to live through.
		Uhhh..No. Yellowstone's Caldera is about 10x the size of Mt. Mazama's, and Tahoe is a basin, not a caldera.
		Lake Tahoe: Was formed by faulting that occurred over millions of years as the Sierra Nevada range rose from a shallow sea to the west and the Carson Range rose to the east.
	www.freerepublic.com /focus/f-news/722866/posts (3092 words)

	How many caldera-forming eruptions have occurred from the long-lived hotspot that is currently beneath Yellowstone? (Site not responding. Last check: 2007-10-25)
		Many eruptive units found along the path of the Yellowstone hotspot have been dated, but only a few of them represent large caldera-forming eruptions.
		At least five volcanic fields centered on large caldera complexes have been identified.
		Some of these caldera complexes erupted climatically more than once; probably 15 to 20 caldera-forming eruptions have occurred along the hotspot as it left a trail from western Idaho to Yellowstone within the past 16.5 million years.
	interactive2.usgs.gov /faq/list_faq_by_category/get_answer.asp?id=926 (123 words)

	The Quaternary pyroclastic succession of southeast Tenerife, Canary Islands: explosive eruptions, related caldera ...
		The Quaternary pyroclastic succession of southeast Tenerife, Canary Islands: explosive eruptions, related caldera subsidence, and sector collapse -- BROWN et al.
		The Quaternary pyroclastic succession of southeast Tenerife, Canary Islands: explosive eruptions, related caldera subsidence, and sector collapse
		the ocean, estimating eruption volumes is virtually impossible.
	geolmag.geoscienceworld.org /cgi/content/abstract/140/3/265 (429 words)

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