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Lahars
A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a 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 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%), hyper-concentrated stream flows (sediment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Armero Tragedy
The Armero tragedy ( ) occurred following the eruption of the Nevado del Ruiz stratovolcano in Tolima Department, Tolima, Colombia, on November 13, 1985. The volcano's eruption after 69 years of dormancy caught nearby towns unprepared, even though volcanological organizations had warned the government to evacuate the area after they detected volcanic activity two months earlier. As pyroclastic flows erupted from the volcanic crater, volcano's crater, they melted the mountain's glaciers, sending four enormous lahars (volcanically induced mudflows, landslides, and debris flows) down its slopes at . The lahars picked up speed in gully, gullies and engulfed the town of Armero, killing more than 20,000 of its almost 29,000 inhabitants. Casualties in other towns, particularly Chinchiná, Caldas, Chinchiná, brought the overall death toll to 23,000. Footage and photographs of Omayra Sánchez, a young victim of the disaster, were published around the world. Other photographs of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Pinatubo
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 Aeta people, Aetas, heavily erosion, eroded and obscured Pinatubo. Pinatubo is known for its Volcanic Explosivity Index, VEI-6 1991 eruption of Mount Pinatubo, 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 (1991), 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nevado Del Ruiz
Nevado del Ruiz (), also known as La Mesa de Herveo () is a volcano on the border of the departments of Caldas and Tolima in Colombia, being the highest point of both. It is located about west of the capital city Bogotá. It is a stratovolcano composed of many layers of lava alternating with hardened volcanic ash and other pyroclastic rocks. Volcanic activity at Nevado del Ruiz began about two million years ago, during the Early Pleistocene or Late Pliocene, with three major eruptive periods. The current volcanic cone formed during the present eruptive period, which began 150,000 years ago. The volcano usually generates Vulcanian to Plinian eruptions, which produce swift-moving currents of hot gas and rock called pyroclastic flows. These eruptions often cause massive lahars (mud and debris flows), which pose a threat to human life and the environment. The impact of such an eruption is increased as the hot gas and lava melt the mountain's snowcap, adding large quantities o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Rainier
Mount Rainier ( ), also known as Tahoma, is a large active stratovolcano in the Cascade Range of the Pacific Northwest in the United States. The mountain is located in Mount Rainier National Park about south-southeast of Seattle. With an officially recognized summit elevation of at the Columbia Crest, it is the highest mountain in the U.S. state of Washington (state), Washington, the most Topographic prominence, topographically prominent mountain in the contiguous United States, and the tallest in the Cascade Volcanic Arc. Due to its high probability of an eruption in the near future and proximity to a Seattle metropolitan area, major urban area, Mount Rainier is considered one of the most dangerous volcanoes in the world, and it is on the Decade Volcano list. The large amount of glacial ice means that Mount Rainier could produce massive lahars that could threaten the entire Puyallup River valley and other river valleys draining Mount Rainier, including the Carbon River, Car ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osceola Lahar
The Osceola Mudflow, also known as the Osceola Lahar, was a debris flow and lahar in the U.S. state of Washington (state), Washington that descended from the summit and northeast slope of Mount Rainier, a volcano in the Cascade Range during a period of eruptions about 5,600 years ago. It traveled down the west and main forks of the White River (Washington), White River, passed the location of present-day Enumclaw, Washington, Enumclaw then reached Puget Sound in several areas, including near the present day sites of Tacoma, Washington, Tacoma and Auburn, Washington, Auburn. The Osceola flow began either as an avalanche or series of avalanches near the summit of Mount Rainier but had transformed to a lahar within of where it was initiated as it incorporated significant amounts of water from within the volcano's hydrothermal system. The sector collapse formed a wide horseshoe-shaped crater, open to the northeast, almost the same size as the crater produced by the 1980 eruptio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tangiwai Disaster
The Tangiwai disaster was a deadly railway accident that occurred at 10:21 p.m. on 24 December 1953, when a railway bridge over the Whangaehu River collapsed beneath an express passenger train at Tangiwai, North Island, New Zealand. The locomotive and the first six carriages derailment, derailed into the river, killing 151 people. The subsequent board of inquiry found that the accident was caused by the failure of the tephra dam holding back nearby Mount Ruapehu's crater lake, creating a rapid mudflow (lahar) in the Whangaehu River which destroyed one of the bridge piers at Tangiwai only minutes before the train reached the bridge. The volcano at Mount Ruapehu was not erupting at the time. The disaster remains New Zealand's worst rail accident. Bridge collapse On 24 December 1953, the 3 p.m. express train from Wellington to Auckland consisted of a NZR KA class, KA class steam locomotive hauling 11 carriages: five second-class, four first-class, a Conductor (railway), Gu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Debris Flow
Debris flows are geological phenomena in which water-laden masses of soil and fragmented Rock (geology), rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally have bulk density, bulk densities comparable to those of rock avalanche, rockslides and other types of landslide classification, landslides (roughly 2000 kilograms per cubic meter), but owing to widespread sediment liquefaction caused by high pore pressure, pore-fluid pressures, they can flow almost as fluidly as water. Debris flows descending steep channels commonly attain speeds that surpass 10 m/s (36 km/h), although some large flows can reach speeds that are much greater. Debris flows with volumes ranging up to about 100,000 cubic meters occur frequently in mountainous regions worldwide. The largest prehistoric flows have had volumes exceeding 1 billion cubic meters (i.e., 1 cubic kilometer). As a result o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Washington (state)
Washington, officially the State of Washington, is a U.S. state, state in the Pacific Northwest region of the United States. It is often referred to as Washington State to distinguish it from Washington, D.C., the national capital, both named after George Washington (the first President of the United States, U.S. president). Washington borders the Pacific Ocean to the west, Oregon to the south, Idaho to the east, and shares Canada–United States border, an international border with the Provinces and territories of Canada, Canadian province of British Columbia to the north. Olympia, Washington, Olympia is the List of capitals in the United States, state capital, and the most populous city is Seattle. Washington is the List of U.S. states and territories by area, 18th-largest state, with an area of , and the List of U.S. states and territories by population, 13th-most populous state, with a population of just less than 8 million. The majority of Washington's residents live ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyroclastic Surge
A pyroclastic surge is a fluidised mass of turbulent gas and rock fragments that is ejected during some volcanic eruptions. It is similar to a pyroclastic flow but it has a lower density or contains a much higher ratio of gas to rock, which makes it more turbulent and allows it to rise over ridges and hills rather than always travel downhill as pyroclastic flows do. The speed of pyroclastic density currents has been measured directly via photography only in the case of Mount St. Helens, where they reached 320-470 km/h, or . Estimates of other modern eruptions are around 360 km/h, or 100 m/s (225 mph). Pyroclastic flows may generate surges. For example, the city of Saint-Pierre, Martinique, Saint-Pierre in Martinique in 1902 was overcome by one. Pyroclastic surge include 3 types, which are base surge, ash-cloud surge, and ground surge. Base surge Base surges were first recognized after the Taal Volcano eruption of 1965 in the Philippines, where a visiting vol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fracture in the Crust (geology), crust, on land or underwater, usually at temperatures from . The volcanic rock resulting from subsequent cooling is often also called ''lava''. A lava flow is an outpouring of lava during an effusive eruption. (An explosive eruption, by contrast, produces a mixture of volcanic ash and other fragments called tephra, not lava flows.) The viscosity of most lava is about that of ketchup, roughly 10,000 to 100,000 times that of water. Even so, lava can flow great distances before cooling causes it to solidify, because lava exposed to air quickly develops a solid crust that insulates the remaining liquid lava, helping to keep it hot and inviscid enough to continue flowing. Etymology The word ''lava'' comes from Ital ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glacier
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land“Glacier, N., Pronunciation.” Oxford English Dictionary, Oxford UP, June 2024, https://doi.org/10.1093/OED/7553486115. Accessed 25 Jan. 2025. and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions, but glaciers may be found in mountain ranges on ever ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitational Energy
Gravitational energy or gravitational potential energy is the potential energy an object with mass has due to the gravitational potential of its position in a gravitational field. Mathematically, it is the minimum mechanical work that has to be done against the gravitational force to bring a mass from a chosen reference point (often an "infinite distance" from the mass generating the field) to some other point in the field, which is equal to the change in the kinetic energies of the objects as they fall towards each other. Gravitational potential energy increases when two objects are brought further apart and is converted to kinetic energy as they are allowed to fall towards each other. Formulation For two pairwise interacting point particles, the gravitational potential energy U is the work that an outside agent must do in order to quasi-statically bring the masses together (which is therefore, exactly opposite the work done by the gravitational field on the masses): U = -W_g = ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
