Mount Hayes
Mount Hayes is the highest mountain in the eastern Alaska Range. Despite not being a fourteener, it is one of the largest peaks in the United States in terms of rise above local terrain. For example, the Northeast Face rises 8,000 feet in 2 miles. In terms of topographic prominence, Mount Hayes is number 51 in the world. Mount Hayes was first climbed in 1941 by Bradford Washburn, Barbara Washburn, Benjamin Ferris, Sterling Hendricks, Henry Hall, William Shand. Today's standard route is the East Ridge. Mount Hayes is not climbed due to its remoteness and the resulting access difficulties. List of mountain peaks of North America List of mountain peaks of the United States List of mountain peaks of Alaska List of Ultras of the United States Michael Wood and Colby Coombs, Alaska: A Climbing Guide, The Mountaineers, 2001. "Mount Hayes, Alaska" on Peakbagger
Volcano
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, gases to escape from a magma chamber below the surface. Earth's volcanoes occur because its crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in its mantle. Therefore, on Earth, volcanoes are found where tectonic plates are diverging or converging, most are found underwater. For example, a mid-oceanic ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can form where there is stretching and thinning of the crust's plates, e.g. in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "plate hypothesis" volcanism. Volcanism away from plate boundaries has been explained as mantle plumes; these so-called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth.
Volcanoes are not created where two tectonic plates slide past one another. Erupting volcanoes can pose many hazards, not only in the immediate vicinity of the eruption. One such hazard is that volcanic ash can be a threat to aircraft, in particular those with jet engines where ash particles can be melted by the high operating temperature. Large eruptions can affect temperature as ash and droplets of sulfuric acid obscure the sun and cool the Earth's lower atmosphere. Volcanic winters have caused catastrophic famines; the word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology. The study of volcanoes is sometimes spelled vulcanology. At the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock; because the crust is thin at these ridges due to the pull of the tectonic plates, the release of pressure leads to adiabatic expansion and the partial melting of the mantle, causing volcanism and creating new oceanic crust.
Most divergent plate boundaries are at the bottom of the oceans. Black smokers are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed. Subduction zones are places where two plates an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or submerges, under the continental plate, forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the melting temperature of the overlying mantle wedge, thus creating magma; this magma tends to be viscous because of its high silica content, so it does not attain the surface but cools and solidifies at depth. When it does reach the surface, however, a volcano is formed. Typical examples are the volcanoes in the Pacific Ring of Fire. Hotspots are volcanic areas believed to be formed by mantle plumes, which are hypothesized to be columns of hot material rising from the core-mantle boundary in a fixed space that causes large-volume melting.
Because tectonic plates move across them, each volcano becomes dormant and is re-formed as the plate advances over the postulated plume. The Hawaiian Islands are said to have been formed in such a manner; this theory, has been doubted. The most common perception of a volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit; the features of volcanoes are much more complicated and their structure and behavior depends on a number of factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have landscape features such as massive plateaus. Vents that issue volcanic material and gases can develop anywhere on the landform and may give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Hawaii's Kīlauea. Other types of volcano include cryovolcanoes on some moons of Jupiter and Neptune. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes except when the mud volcano is a vent of an igneous volcano.
Volcanic fissure vents are linear fractures through which lava emerges. Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent, they do not explode catastrophically. Since low-viscosity magma is low in silica, shield volcanoes are more common in oceanic than continental settings; the Hawaiian volcanic chain is a series of shield cones, they are common in Iceland, as well. Lava domes are built by slow eruptions of viscous lava, they are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount Saint Helen
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, the natural hazards that threaten it; the organization has four major science disciplines, concerning biology, geography and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility; the USGS is a bureau of the United States Department of the Interior. The USGS employs 8,670 people and is headquartered in Reston, Virginia; the USGS has major offices near Lakewood, Colorado, at the Denver Federal Center, Menlo Park, California. The current motto of the USGS, in use since August 1997, is "science for a changing world." The agency's previous slogan, adopted on the occasion of its hundredth anniversary, was "Earth Science in the Public Service." Since 2012, the USGS science focus is directed at six topical "Mission Areas", namely Climate and Land Use Change, Core Science Systems, Ecosystems and Minerals and Environmental Health, Natural Hazards, Water.
In December 2012, the USGS split the Energy and Minerals and Environmental Health Mission Area resulting in seven topical Mission Areas, with the two new areas being: Energy and Minerals and Environmental Health. Administratively, it is divided into six Regional Units. Other specific programs include: Earthquake Hazards Program monitors earthquake activity worldwide; the National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location and magnitude of global earthquakes. The USGS runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System; the USGS informs authorities, emergency responders, the media, the public, both domestic and worldwide, about significant earthquakes. It maintains long-term archives of earthquake data for scientific and engineering research, it conducts and supports research on long-term seismic hazards. USGS has released the UCERF California earthquake forecast.
As of 2005, the agency is working to create a National Volcano Early Warning System by improving the instrumentation monitoring the 169 volcanoes in U. S. territory and by establishing methods for measuring the relative threats posed at each site. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time; the USGS collaborates with Canadian and Mexican government scientists, along with the Commission for Environmental Cooperation, to produce the North American Environmental Atlas, used to depict and track environmental issues for a continental perspective. The USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online. National Climate Change and Wildlife Science Center implements partner-driven science to improve understanding of past and present land use change, develops relevant climate and land use forecasts, identifies lands and communities that are most vulnerable to adverse impacts of change from the local to global scale.
Since 1962, the Astrogeology Research Program has been involved in global and planetary exploration and mapping. In collaboration with Stanford University, the USGS operates the USGS-Stanford Ion Microprobe Laboratory, a world-class analytical facility for U--Pb geochronology and trace element analyses of minerals and other earth materials. USGS operates a number of water related programs, notably the National Streamflow Information Program and National Water-Quality Assessment Program. USGS Water data is publicly available from their National Water Information System database; the USGS operates the National Wildlife Health Center, whose mission is "to serve the nation and its natural resources by providing sound science and technical support, to disseminate information to promote science-based decisions affecting wildlife and ecosystem health. The NWHC provides information, technical assistance, research and leadership on national and international wildlife health issues." It is the agency responsible for surveillance of H5N1 avian influenza outbreaks in the United States.
The USGS runs 17 biological research centers in the United States, including the Patuxent Wildlife Research Center. The USGS is investigating collaboration with the social networking site Twitter to allow for more rapid construction of ShakeMaps; the USGS produces several national series of topographic maps which vary in scale and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest and best-known topographic series is the 7.5-minute, 1:24,000 scale, quadrangle, a non-metric scale unique to the United States. Each of these maps covers an area bounded by two lines of latitude and two lines of longitude spaced 7.5 minutes apart. Nearly 57,000 individual maps in this series cover the 48 contiguous states, Hawaii, U. S. territories, areas of Alaska near Anchorage and Prudhoe Bay. The area covered by each map varies with the latitude of its represented location due to convergence of the meridians. At lower latitudes, near 30° north, a 7.5-minute quadrangle contains an area of about 64 square miles.
At 49° north latitude, 49 square miles are contained within a quadrangle of that size. As a unique non-metric map scale, the 1:24,000 scale requires a separate and specialized romer scale for pl
Mount Fairweather
Mount Fairweather, is the highest mountain in the Canadian province of British Columbia, with an elevation of 4,671 metres. It is located 20 km east of the Pacific Ocean on the border of Alaska, United States and western British Columbia, Canada. Most of the mountain lies within Glacier Bay National Park and Preserve in the City and Borough of Yakutat, though the summit borders Tatshenshini-Alsek Provincial Park, British Columbia, it is designated as Boundary Peak 164 or as US/Canada Boundary Point #164. The mountain was named on May 3, 1778 by Captain James Cook for the unusually good weather encountered at the time; the name has been translated into many languages. It was called "Mt. Beautemps" by La Perouse, "Mte. Buen-tiempo" by Galiano, "Gor-Khoroshy-pogody" on Russian Hydrographic Dept. Chart 1378 in 1847, "G Fayerveder" by Captain Tebenkov, Imperial Russian Navy, it was called "Schönwetterberg" by Constantin Grewingk in 1850 and "Schönwetter Berg" by Justus Perthes in 1882. Fairweather was first climbed in 1931 by Allen Carpé and Terris Moore.
Mount Fairweather is located right above Glacier Bay in the Fairweather Range of the Saint Elias Mountains. Mount Fairweather marks the northwest extremity of the Alaska Panhandle. Like many peaks in the St. Elias Mountains, Mount Fairweather has great vertical relief due to its dramatic rise from Glacier Bay. However, due to poor weather in the area, this effect is obscured with the clouds which hides the summit from view. Known in the Tlingit language as Tsalxhaan, it is said this mountain and Yaas'éit'aa Shaa were next to each other but had an argument and separated, their children, the mountains in between the two peaks, are called Tsalxhaan Yatx'i Despite its name, Mount Fairweather has harsh weather conditions. It receives over 100 inches of precipitation each year and sees temperatures of around -50 °F. 1926 Allen Carpe, Andy Taylor and W. S. Ladd reached 2,890 m on the West Ridge, but were forced back due to a steep notch in the ridge that made ferrying supplies difficult. 1930 Bradford Washburn made an attempt on the West Ridge but traveling conditions forced a retreat at 2,040 metres.
1931 Allen Carpe and Terris Moore summited via the Southeast Ridge on June 8, 1931 1958 Paddy Sherman and 7 other Canadians reached the summit via the SE Ridge on June 26, 1958. 1968 West Ridge, Loren Adkins, Walter Gove, Paul Myhre, John Neal and Kent Stokes - summit reached June 12, 1968 1973 Southwest Ridge, Peter Metcalf, Henry Florschutz, Toby O'Brien and Lincoln Stoller. Summit reached on July 10, 1973. After failing to reach the summit in 1926 due to terrain difficulty on their chosen route, Allen Carpe, W. S. Ladd, Andy Taylor returned in 1931 along with a new member Terry Moore. In early April the group began their approach by boat but stormy weather delayed them rounding Cape Fairweather until April 17, they unloaded their supplies on the beach. Backtracking 21 kilometres along the coast, they made their way to the Fairweather Glacier. From base camp in a spot they called Paradise Valley, they decided to attempt the mountain from the south rather than via the west ridge. Due to deep snow, they realized that skis and snowshoes would be of great help so Carpe and Moore made the 80 km round trip to fetch them from Lituya Bay.
They ascended the glacier from base setup camp at 1,520 m on the mountain's south face. On May 25, they established high camp at 2,740 m after making significant progress up a ridge on a rare day of good weather. However, the weather turned and they were forced to descend after an overnight coating of snow. After waiting out the snowstorm for six days at lower camp, they made their way back up to high camp on June 2, they left for the summit at 1:30 am on June 3 and having reached the southeast shoulder by mid-morning, they were feeling so confident that they left the willow wands behind. However, higher altitude and the weeks of hard effort slowed their progress and the weather changed. By 1 pm not far from the summit, they decided to retreat and had to descend without the wands to guide them, they managed to reach the tents by 4 pm. Ladd and Taylor volunteered to descend due to dwindling supplies at high camp with the hope that Carpe and Moore would be able to make another attempt in good weather.
The storm raged for four days before it cleared in the evening on June 7. At 10 pm, Carpe and Moore set out for the summit and with no further difficulties made it to the top. List of mountain peaks of North America List of mountain peaks of Canada List of mountain peaks of the United States List of Boundary Peaks of the Alaska-British Columbia/Yukon border NOAA Ship Fairweather Sherman, Paddy. Cloud Walkers. MacMillan. ISBN 0-916890-79-1
Mount Blackburn
Mount Blackburn is the highest peak in the Wrangell Mountains of Alaska in the United States. It is the twelfth-highest peak in North America; the mountain is an old, eroded shield volcano, the second-highest volcano in the U. S. behind Mount Bona and the fifth-highest in North America. It was named in 1885 by Lt. Henry T. Allen of the U. S. Army after Joseph Clay Stiles Blackburn, a U. S. senator from Kentucky. It is located in the heart of Wrangell – St. Elias National Park, the largest national park in the country; the mountain's massif is covered entirely by icefields and glaciers, is the principal source of ice for the Kennicott Glacier, which flows southeast over 20 miles to just above the town of McCarthy. The mountain contributes a large volume of ice to the north-flowing Nabesna Glacier and the Kuskulana Glacier system. Mount Blackburn is a large, dramatic peak, with great local relief and independence from higher peaks, its west face drops over 11,000 ft to the Kuskulana Glacier in less than 4 horizontal miles.
Its other faces drop 8,000–10,000 ft, all in less than 8 miles. The toe of the Kuskulana Glacier, less than 12 miles from the summit, lies at an elevation of 2,400 ft, giving a rise of 14,000 ft. While these figures speak to the peak's relief, one measure of its independence is that it is the 50th-most topographically prominent peak in the world; the western of Blackburn's two summits is the mountain's highest point, a fact, not understood until the 1960s when new USGS maps were published. The first ascent of the west peak, hence Mount Blackburn, was done on May 30, 1958, by Bruce Gilbert, Dick Wahlstrom, Hans Gmoser, Adolf Bitterlich, Leon Blumer via the North Ridge; this team made the first ascent of Blackburn, but did not know it at the time due to the incorrect identification of the highest point. In fact, Blumer's article in the 1959 American Alpine Journal is titled "Mount Blackburn – Second Ascent." Kennedy Peak, or East Blackburn, 16,286 ft, is the eastern summit and was thought to be the highest point.
The first ascent of this summit was made in 1912 by Dora Keen and George Handy via the Kennicott Glacier and East Face. This heady exploit was ahead of its time. Dora Keen, driven by a deep desire for the climb, solicited miners from the nearby Kennecott Copper Mines, forged a route up the crevassed East Face to the East Peak, but did not traverse over to the West Peak. Keen went on to write a famous article for the Saturday Evening Post titled, "First up Mount Blackburn." In 1912, Keen and Handy thought. Mount Blackburn represents the eroded core of a shield volcano; because it is shrouded in permanent ice, its internal structure cannot be determined. It is believed to have a summit caldera modified by glaciation; the oldest rocks in the area are granites, about 4.2 million years old, representing an intrusive mass. The majority of the mountain is 3.4 million year old granite. From this it is inferred that a caldera collapse took place between 4.2 and 3.4 million years ago, after which activity ceased.
Today's standard route on the peak is the 1958 ascent route, the North Ridge, approached from the Nabesna Glacier, on the north side of the mountain, opposite from Keen and Hardy's route. The route starts from an airstrip on the glacier at an altitude of 7,200 feet, it is a moderate climb by Alaskan standards. List of mountain peaks of North America List of mountain peaks of the United States List of mountain peaks of Alaska List of the highest major summits of the United States List of the most prominent summits of the United States List of the most isolated major summits of the United States List of volcanoes in the United States Wood, Michael. Alaska: A Climbing Guide. Mountaineers Books. ISBN 0-89886-724-X. Richter, Donald H.. Guide to the Volcanoes of the Western Wrangell Mountains, Alaska. USGS Bulletin 2072. Winkler, Gary R.. A Geologic Guide to Wrangell—Saint Elias National Park and Preserve, Alaska: A Tectonic Collage of Northbound Terranes. USGS Professional Paper 1616. ISBN 0-607-92676-7.
Richter, Donald H.. Geologic Map of the Wrangell-Saint Elias National Park and Preserve, Alaska. USGS Scientific Investigations Map 2877
Mountain range
A mountain range or hill range is a series of mountains or hills ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form and alignment that have arisen from the same cause an orogeny. Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics. Mountain ranges are found on many planetary mass objects in the Solar System and are a feature of most terrestrial planets. Mountain ranges are segmented by highlands or mountain passes and valleys. Individual mountains within the same mountain range do not have the same geologic structure or petrology, they may be a mix of different orogenic expressions and terranes, for example thrust sheets, uplifted blocks, fold mountains, volcanic landforms resulting in a variety of rock types. Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or the Alpide Belt.
The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera along the Pacific Coast, the Aleutian Range, on through Kamchatka, Taiwan, the Philippines, Papua New Guinea, to New Zealand. The Andes is 7,000 kilometres long and is considered the world's longest mountain system; the Alpide belt includes Indonesia and Southeast Asia, through the Himalaya, Caucasus Mountains, Balkan Mountains fold mountain range, the Alps, ends in the Spanish mountains and the Atlas Mountains. The belt includes other European and Asian mountain ranges; the Himalayas contain the highest mountains in the world, including Mount Everest, 8,848 metres high and traverses the border between China and Nepal. Mountain ranges outside these two systems include the Arctic Cordillera, the Urals, the Appalachians, the Scandinavian Mountains, the Great Dividing Range, the Altai Mountains and the Hijaz Mountains. If the definition of a mountain range is stretched to include underwater mountains the Ocean Ridges form the longest continuous mountain system on Earth, with a length of 65,000 kilometres.
The mountain systems of the earth are characterized by a tree structure, where mountain ranges can contain sub-ranges. The sub-range relationship is expressed as a parent-child relationship. For example, the White Mountains of New Hampshire and the Blue Ridge Mountains are sub-ranges of the Appalachian Mountains. Equivalently, the Appalachians are the parent of the White Mountains and Blue Ridge Mountains, the White Mountains and the Blue Ridge Mountains are children of the Appalachians; the parent-child expression extends to the sub-ranges themselves: the Sandwich Range and the Presidential Range are children of the White Mountains, while the Presidential Range is parent to the Northern Presidential Range and Southern Presidential Range. The position of mountains influences climate, such as snow; when air masses move up and over mountains, the air cools producing orographic precipitation. As the air descends on the leeward side, it warms again and is drier, having been stripped of much of its moisture.
A rain shadow will affect the leeward side of a range. Mountain ranges are subjected to erosional forces which work to tear them down; the basins adjacent to an eroding mountain range are filled with sediments which are buried and turned into sedimentary rock. Erosion is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains; the early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet of Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to the east; this mass of rock was removed as the range was undergoing uplift. The removal of such a mass from the core of the range most caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment.
Computer simulation has shown that as mountain belts change from tectonically active to inactive, the rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System are isolated and formed by processes such as impacts, though there are examples of mountain ranges somewhat similar to those on Earth. Saturn's moon Titan and Pluto, in particular exhibit large mountain ranges in chains composed of ices rather than rock. Examples include the Mithrim Montes and Doom Mons on Titan, Tenzing Montes and Hillary Montes on Pluto; some terrestrial planets other than Earth exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars, Jupiter's moon Io has mountain ranges formed from tectonic processes including Boösaule Montes, Dorian Montes, Hi'iaka Montes and Euboea Montes. Peakbagger Ranges Home Page Bivouac.com
Stratovolcano
A stratovolcano known as a composite volcano, is a conical volcano built up by many layers of hardened lava, tephra and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas; the lava flowing from stratovolcanoes cools and hardens before spreading far, due to high viscosity. The magma forming this lava is felsic, having high-to-intermediate levels of silica, with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows have travelled as far as 15 km. Stratovolcanoes are sometimes called "composite volcanoes" because of their composite stratified structure built up from sequential outpourings of erupted materials, they are in contrast to the less common shield volcanoes. Two famous examples of stratovolcanoes are Krakatoa, known for its catastrophic eruption in 1883 and Vesuvius, whose eruption in AD79 caused destruction of Pompeii and Herculaneum in 79 AD.
Both eruptions claimed thousands of lives. In modern times, Mount St. Helens and Mount Pinatubo have erupted catastrophically, with lesser losses of lives; the possible existence of stratovolcanoes on other terrestrial bodies of the Solar System has not been conclusively demonstrated. The one feasible exception are the existence of some isolated massifs on Mars, for example the Zephyria Tholus. Stratovolcanoes are common at subduction zones, forming chains and clusters along plate tectonic boundaries where oceanic crust is drawn under continental crust or another oceanic plate; the magma forming stratovolcanoes rises when water trapped both in hydrated minerals and in the porous basalt rock of the upper oceanic crust is released into mantle rock of the asthenosphere above the sinking oceanic slab. The release of water from hydrated minerals is termed "dewatering", occurs at specific pressures and temperatures for each mineral, as the plate descends to greater depths; the water freed from the rock lowers the melting point of the overlying mantle rock, which undergoes partial melting and rises due to its lighter density relative to the surrounding mantle rock, pools temporarily at the base of the lithosphere.
The magma rises through the crust, incorporating silica-rich crustal rock, leading to a final intermediate composition. When the magma nears the top surface, it pools in a magma chamber within the crust below the stratovolcano. There, the low pressure allows water and other volatiles dissolved in the magma to escape from solution, as occurs when a bottle of carbonated water is opened, releasing CO2. Once a critical volume of magma and gas accumulates, the plug of the volcanic vent is broken, leading to a sudden explosive eruption. In recorded history, explosive eruptions at subduction zone volcanoes have posed the greatest hazard to civilizations. Subduction-zone stratovolcanoes, such as Mount St. Helens, Mount Etna and Mount Pinatubo erupt with explosive force: the magma is too stiff to allow easy escape of volcanic gases; as a consequence, the tremendous internal pressures of the trapped volcanic gases remain and intermingle in the pasty magma. Following the breaching of the vent and the opening of the crater, the magma degasses explosively.
The magma and gases blast out with full force. Since 1600 CE, nearly 300,000 people have been killed by volcanic eruptions. Most deaths were caused by pyroclastic flows and lahars, deadly hazards that accompany explosive eruptions of subduction-zone stratovolcanoes. Pyroclastic flows are swift, avalanche-like, ground-sweeping, incandescent mixtures of hot volcanic debris, fine ash, fragmented lava and superheated gases that can travel at speeds in excess of 160 km/h. Around 30,000 people were killed by pyroclastic flows during the 1902 eruption of Mount Pelée on the island of Martinique in the Caribbean. In March to April 1982, three explosive eruptions of El Chichón in the State of Chiapas in southeastern Mexico, caused the worst volcanic disaster in that country's history. Villages within 8 km of the volcano were destroyed by pyroclastic flows, killing more than 2,000 people. Two Decade Volcanoes that erupted in 1991 provide examples of stratovolcano hazards. On June 15, Mount Pinatubo spewed an ash cloud 40 km into the air and produced huge pyroclastic surges and lahar floods that devastated a large area around the volcano.
Pinatubo, located in Central Luzon just 90 km west-northwest from Manila, had been dormant for 6 centuries before the 1991 eruption, which ranks as one of the largest eruptions in the 20th century. In 1991, Japan's Unzen Volcano, located on the island of Kyushu about 40 km east of Nagasaki, awakened from its 200-year slumber to produce a new lava dome at its summit. Beginning in June, repeated collapse of this erupting dome generated ash flows that swept down the mountain's slopes at speeds as high as 200 km/h. Unzen is one of more than 75 active volcanoes in Japan; the eruption of Mount Vesuvius in 79 smothered the nearby ancient cities of Pompeii and Herculaneum with thick deposits of pyroclastic surges and lava flows. Although death toll is estimated between 13,000 and 26,000 remains, the exact number still remains unknown. Vesuvius is recognized as one of the most dangerous volcanoes, due to its
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