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1991 Eruption Of Mount Pinatubo
The 1991 eruption of Mount Pinatubo in the Philippines' Luzon Volcanic Arc was the second-largest volcanic eruption of the 20th century, behind only the 1912 eruption of Novarupta in Alaska. Eruptive activity began on April 2 as a series of phreatic eruption, phreatic explosions from a fissure that opened on the north side of Mount Pinatubo. Seismographs were set up and began monitoring the volcano for earthquakes. In late May, the number of seismic events under the volcano fluctuated from day-to-day. Beginning June 6, a swarm of progressively shallower earthquakes accompanied by Deformation (volcanology), inflationary tilt on the upper east flank of the mountain, culminated in the extrusion of a small lava dome. On June 12, the volcano's first spectacular eruption sent an eruption column, ash column into the atmosphere. Additional explosions occurred overnight and the morning of June 13. Seismic activity during this period became intense. When even more highly gas-charged m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Volcanism Program
The Smithsonian Institution's Global Volcanism Program (GVP) documents Earth's volcanoes and their eruptive history during the Quaternary Period of Earth's geologic history, with particular emphasis on volcanic activity during the Holocene Epoch (the last 11,700 years). The mission of the GVP is to document, understand, and disseminate information about global volcanic activity. Global Volcanism Program Database The GVP gathers information and reports on current eruptions from around the world, and maintains a database repository on active volcanoes, their eruptions and their eruption histories. In this way, a global context for the planet's active volcanism is presented. Smithsonian reporting on current volcanic activity dates back to 1968, with the Center for Short-Lived Phenomena (CSLP). The GVP is housed in the Department of Mineral Sciences, part of the National Museum of Natural History, on the National Mall in Washington, D.C. During the early stages of an eruption, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phreatic Eruption
A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from ) causes near-instantaneous evaporation of water to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs. At Mount St. Helens in Washington state, hundreds of steam explosions preceded the 1980 Plinian eruption of the volcano. A less intense geothermal event may result in a mud volcano. Phreatic eruptions typically include steam and rock fragments; the inclusion of liquid lava is unusual. The temperature of the fragments can range from cold to incandescent. If molten magma is included, volcanologists classify the event as a phreatomagmatic eruption. These eruptions occasionally create broad, low-relief craters called '' maars''. Phreatic explosions can be accompanied by carbon dioxide or hydrogen sulfide gas-emissions. Carbon diox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinatubo 1991 (before)
Mount Pinatubo is an active stratovolcano in the Zambales Mountains in Luzon in the Philippines. Located on the tripoint of Zambales, Tarlac and Pampanga provinces, most people were unaware of its eruptive history before the pre-eruption volcanic activity in early 1991. Dense forests, which supported a population of several thousand indigenous Aetas, heavily eroded and obscured Pinatubo. Pinatubo is known for its VEI-6 eruption on June 15, 1991, the second-largest terrestrial eruption of the 20th century after the 1912 eruption of Novarupta in Alaska. The eruption coincided with Typhoon Yunya making landfall in the Philippines, which brought a dangerous mix of ash and rain to nearby towns and cities. Early predictions led to the evacuation of tens of thousands of people, saving many lives. The eruption severely damaged surrounding areas with pyroclastic surges, pyroclastic falls, and later, flooding lahars caused by rainwater re-mobilizing volcanic deposits. This destruct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clark Air Base
Clark Air Base is a Philippine Air Force base in Luzon, located west of Angeles City, and about northwest of Metro Manila. It was previously operated by the U.S. Air Force and, before that, the U.S. Army, from 1903 to 1991. The base covered with a military reservation extending north that covered another . The base was a stronghold of combined Philippine and American forces during the final months of World War II, and a backbone of logistical support during the Vietnam War until 1975. Following the departure of American forces in 1991 due to the eruption of Mount Pinatubo and rejection by the Philippine Senate for renewing the presence of U.S. military bases in the Philippines, the base became the site of Clark International Airport, as well as the Clark Freeport Zone and the Air Force City of the Philippine Air Force. In April 2016, an air contingent of USAF A-10s and HH-60s was deployed from US air bases in Pyeongtaek and Okinawa to Clark. The air contingen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lahar
A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of Pyroclastic rock, pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a valley, river valley. Lahars are often extremely destructive and deadly; they can flow tens of metres per second, they have been known to be up to deep, and large flows tend to destroy any structures in their path. Notable lahars include those at Mount Pinatubo in the Philippines and Nevado del Ruiz in Colombia, the latter of which killed more than 20,000 people in the Armero tragedy. Etymology The word ''lahar'' is of Javanese language, Javanese origin. Berend George Escher introduced it as a geological term in 1922. Description The word ''lahar'' is a general term for a flowing mixture of water and pyroclastic debris. It does not refer to a particular rheology or sediment concentration. Lahars can occur as normal stream flows (sediment concentration of less than 30%), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), Australia to the east. To the south it is bounded by the Southern Ocean or Antarctica, depending on the definition in use. The Indian Ocean has large marginal or regional seas, including the Andaman Sea, the Arabian Sea, the Bay of Bengal, and the Laccadive Sea. Geologically, the Indian Ocean is the youngest of the oceans, and it has distinct features such as narrow continental shelf, continental shelves. Its average depth is 3,741 m. It is the warmest ocean, with a significant impact on global climate due to its interaction with the atmosphere. Its waters are affected by the Indian Ocean Walker circulation, resulting in unique oceanic currents and upwelling patterns. The Indian Ocean is ecologically diverse, with important ecosystems such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the structural integrity of such a chamber, greatly diminishing its capacity to support its own roof and any substrate or rock resting above. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large depression at the surface (from one to dozens of kilometers in diameter). Although sometimes described as a Volcanic crater, crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur over the course of a century, the formation of a caldera is a rare event, occurring only a few times within a given window of 100 years. Only eight caldera-forming collapses are known to have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyroclastic Flow
A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of but is capable of reaching speeds up to . The gases and tephra can reach temperatures of about . Pyroclastic flows are the deadliest of all volcanic hazards and are produced as a result of certain explosive eruptions; they normally touch the ground and hurtle downhill or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope. Origin of term The word ''pyroclast'' is derived from the Greek (''pýr''), meaning "fire", and (''klastós''), meaning "broken in pieces". A name for pyroclastic flows that glow red in the dark is (French, "burning cloud"); this was notably used to describe the disastrous 1902 eruption of Mount Pelée on Martinique, a Frenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pumice
Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular volcanic rock that differs from pumice in having larger vesicles, thicker vesicle walls, and being dark colored and denser.Jackson, J.A., J. Mehl, and K. Neuendorf (2005) ''Glossary of Geology'' American Geological Institute, Alexandria, Virginia. 800 pp. McPhie, J., M. Doyle, and R. Allen (1993) ''Volcanic Textures A guide to the interpretation of textures in volcanic rocks'' Centre for Ore Deposit and Exploration Studies, University of Tasmania, Hobart, Tasmania..198 pp. Pumice is created when super-heated, highly pressurized rock is rapidly ejected from a volcano. The unusual foamy configuration of pumice happens because of simultaneous rapid cooling and rapid depressurization. The depressurization creates bubbles by lowering the sol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Ash
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as '' tephra''), including particles larger than 2 mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the gases shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometres away. Due to its wide dispersal, ash can have a number of impacts on society, including animal a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. Besides molten rock, magma may also contain suspended crystals and volcanic gas, gas bubbles. Magma is produced by melting of the mantle (geology), mantle or the Crust (geology), crust in various tectonics, tectonic settings, which on Earth include subduction zones, continental rift (geology), rift zones, mid-ocean ridges and Hotspot (geology), hotspots. Mantle and crustal melts migrate upwards through the crust where they are thought to be stored in magma chambers or trans-crustal crystal mush, crystal-rich mush zones. During magma's storage in the crust, its composition may be modified by Fractional crystallization (geology), fractional crystallization, contaminati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eruption Column
An eruption column or eruption plume is a cloud of super-heated Volcanic ash, ash and tephra suspended in volcanic gas, gases emitted during an explosive eruption, explosive volcanic eruption. The volcanic materials form a vertical column or Plume (fluid dynamics), plume that may rise many kilometers into the air above the vent of the volcano. In the most explosive eruptions, the eruption column may rise over , penetrating the stratosphere. Injection of Particulate, aerosols into the stratosphere by volcanoes is a major cause of short-term Volcanic winter, climate change. A common occurrence in explosive eruptions is ''column collapse'' when the eruption column is or becomes too dense to be lifted high into the sky by air convection, and instead falls down the slopes of the volcano to form pyroclastic flows or pyroclastic surge, surges (although the latter is less dense). On some occasions, if the material is not dense enough to fall, it may create pyrocumulonimbus clouds. Forma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
