[edit]Mexico
Volcanoes of Mexico are related to subduction of the Cocos and Rivera plates to the east, which has produced large explosive eruptions. Most active volcanoes in Mexico occur in the Trans-Mexican Volcanic Belt, which extends 900 kilometres (559 mi) from west to east across central-southern Mexico. A few other active volcanoes in northern Mexico are related to extensional tectonics of the Basin and Range Province, which split the Baja California peninsula from the mainland.[12] Popocatépetl lies in the eastern half of the Trans-Mexican Volcanic Belt, which is the second highest peak in Mexico after the Pico de Orizaba. It is one of most active volcanoes in Mexico, having had more than 20 major eruptions since the arrival of the Spanish in 1519. The 1982 eruption of El Chichónkilled about 2,000 people who lived near the volcano. It created a 1 kilometre (1 mi) wide caldera that filled with an acidic crater lake. Prior to 2000, this relatively unknown volcano was heavily forested and of no greater height than adjacent non-volcanic peaks.[12]
[edit]United States
In the western United States lies the Cascade Volcanic Arc. It includes nearly 20 major volcanoes, among a total of over 4,000 separate volcanic vents including numerousstratovolcanoes, shield volcanoes, lava domes, and cinder cones, along with a few isolated examples of rarer volcanic forms such as tuyas. Volcanism in the arc began about 37 million years ago, however, most of the present-day Cascade volcanoes are less than 2,000,000 years old, and the highest peaks are less than 100,000 years old. It formed by subduction of the Gorda and Juan de Fuca plates at the Cascadia subduction zone. This is a 680 mi (1,090 km) long fault, running 50 mi (80 km) off the west-coast of the Pacific Northwest from northern California to Vancouver Island, British Columbia. The plates move at a relative rate of over 0.4 inches (10 mm) per year at a somewhat oblique angle to the subduction zone.
Because of the very large fault area, the Cascadia subduction zone can produce very large earthquakes, magnitude 9.0 or greater, if rupture occurred over its whole area. When the "locked" zone stores energy for an earthquake, the "transition" zone, although somewhat plastic, can rupture. Thermal and deformation studies indicate that the locked zone is fully locked for 60 kilometers (about 40 miles) down-dip from the deformation front. Further down-dip, there is a transition from
fully locked to aseismic sliding.
Unlike most subduction zones worldwide, there is no oceanic trench present along thecontinental margin in Cascadia. Instead, terranes and the accretionary wedge have been uplifted to form a series of coast ranges and exotic mountains. A high rate of sedimentation from the outflow of the three major rivers (Fraser River, Columbia River, and Klamath River) which cross the Cascade Range contributes to further obscuring the presence of a trench. However, in common with most other subduction zones, the outer margin is slowly being compressed, similar to a giant spring. When the stored energy is suddenly released by slippage across the fault at irregular intervals, the Cascadia subduction zone can create very large earthquakes such as the magnitude 9Cascadia earthquake of 1700. Geological evidence indicates that great earthquakes may have occurred at least seven times in the last 3,500 years, suggesting a return time of 400 to 600 years. There is also evidence of accompanying tsunamis with every earthquake, as the prime reason they know of these earthquakes is through "scars" the tsunami left on the coast, and throughJapanese records (tsunami waves can travel across the Pacific).
The 1980 eruption of Mount St. Helens was the most significant to occur in the contiguous 48 U.S. states in recorded history (VEI= 5, 0.3 cu mi, 1.2 km3 of material erupted), exceeding the destructive power and volume of material released by the 1915 eruption of California's Lassen Peak. The eruption was preceded by a two-month series of earthquakes and steam-venting episodes, caused by an injection of magma at shallow depth below the mountain that created a huge bulge and a fracture system on Mount St. Helens' north slope. An earthquake at 8:32 a.m. on May 18, 1980, caused the entire weakened north face to slide away, suddenly exposing the partly molten, gas- and steam-rich rock in the volcano to lower pressure. The rock responded by exploding into a very hot mix of pulverized lava and older rock that sped toward Spirit Lake so fast that it quickly passed the avalanching north face.
Alaska is known for its seismic and volcanic activity, holding the record for the second largest earthquake in the world the Good Friday Earthquake, and having more than 50 volcanoes which have erupted since about 1760.[13] Volcanoes can be found not only in the mainland but also in the Aleutian Islands.
The most recent activity in the American portion of the Ring of Fire occurred in early 2009 when Mount Redoubt in Alaska became active and finally erupted late in the evening of March 22. The eruption ended in May 2009.
[edit]Canada
See also: Volcanism in Canada
British Columbia and Yukon are home to a vast region of volcanoes and volcanic activity in the Pacific Ring of Fire.[14] Several mountains that many British Columbians look at every day are dormant volcanoes. Most of them have erupted during the Pleistocene and Holocene. Although none of Canada's volcanoes are currently erupting, several volcanoes, volcanic fields and volcanic centers are considered potentially active.[15] There are hot springs at some volcanoes while 10 volcanoes in British Columbia appear related to seismic activity since 1975, including: the Silverthrone Caldera,Mount Meager, Wells Gray-Clearwater volcanic field, Mount Garibaldi, Mount Cayley, Castle Rock, The Volcano, Mount Edziza, Hoodoo Mountain, Crow Lagoon and Nazko Cone.[16] The volcanoes are grouped into five volcanic belts with different tectonic settings.
The Northern Cordilleran Volcanic Province (sometimes known as the Stikine Volcanic Belt) is the most active volcanic region in Canada. It formed due to extensional cracking, faulting and rifting of the North American Plate, as the Pacific Plate grinds and slides past the Queen Charlotte Fault, unlike subduction that produces the volcanoes in Japan, Philippines and Indonesia. The region has Canada's largest volcanoes,[14]much larger than the minor stratovolcanoes found in the Canadian portion of the Cascade Volcanic Arc.[14]Several eruptions are known to have occurred within the last 400 years. Mount Edziza is a huge volcanic complex that erupted several times in the past several thousand of years, which has formed several cinder cones and lava flows. The complex comprises the Mount Edziza Plateau, a large volcanic plateau (65 kilometers long and 20 kilometers wide) made of predominantly basaltic lava flows with four large stratovolcanoes built on top of the plateau. The associated lava domes and satellite cones were constructed over the past 7.5 million years during five magmatic cycles beginning with eruption ofalkali basalts and ending with felsic and basaltic eruptions as late as 1,340 years ago. The blocky lava flows still maintain their original forms. Hoodoo Mountain is a tuya in northwestern British Columbia, which has had several periods of subglacial eruptions. The oldest eruptions occurred about 100,000 years ago and the most recent being about 7000 years ago. Hoodoo Mountain is also considered active and could erupt in the future. The nearby Tseax Cone and The Volcano produced some of Canada's youngest lava flows, that are about 150 years old.
Canada's worst known geophysical disaster came from the Tseax Cone during the 18th century at the southernmost end of the volcanic belt. The eruption produced a 22.5 km long lava flow, destroying the Nisga'a villages and the death of at least 2000 Nisga'a people by volcanic gases and poisonous smoke. The Nass River valley was inundated by the lava flows and contains abundant tree molds and lava tubes. The event happened at the same time with the arrival of the first European explorers to penetrate the uncharted coastal waters of northern British Columbia. Today, the basaltic lava deposits are a draw to tourists and are part of the Nisga'a Memorial Lava Beds Provincial Park.
The Garibaldi Volcanic Belt in southwestern British Columbia, is the northern extension of the Cascade Volcanic Arc in the United States (which includes Mount Baker and Mount St. Helens) and contains the most explosive young volcanoes in Canada.[17] It formed as a result of subduction of theJuan de Fuca Plate (a remnant of the much larger Farallon Plate) under the North American Plate along the Cascadia subduction zone.[17] The Garibaldi Volcanic Belt includes the Bridge River Cones, Mount Cayley, Mount Fee, Mount Garibaldi, Mount Price, Mount Meager, the Squamish Volcanic Field and much more smaller volcanoes. The eruption styles in the belt range from effusive to explosive, with compositions from basalt to rhyolite. Morphologically, centers include calderas, cinder cones, stratovolcanoes and small isolated lava masses. Due to repeated continental and alpine glaciations, many of the volcanic deposits in the belt reflect complex interactions between magma composition, topography, and changing ice configurations. The most recent major catastrophic eruption in the Garibaldi Volcanic Belt was the 2350 BP eruption of Mount Meager as well as Canada. It was similar the 1980 eruption of Mount St. Helens,[17] sending an ash column approximately 20 km high into the stratosphere.[18]
The Chilcotin Group is a north-south range of volcanoes in southern British Columbia running parallel to the Garibaldi Volcanic Belt. The majority of the eruptions in this belt happened either 6–10 million years ago (Miocene) or 2–3 million years ago (Pliocene), although there have been some slightly more recent eruptions (in the Pleistocene).[19] It is thought to have formed as a result of back-arc extension behind the Cascadia subduction zone.[19] Volcanoes in this belt include Mount Noel, the Clisbako Caldera Complex, Lightning Peak, Black Dome Mountain and many lava flows.
The Anahim Volcanic Belt is a line of volcanoes stretching from just north of Vancouver Island to near Quesnel, British Columbia,Canada. These volcanoes were formed 8-1 million years ago and the Nazko Cone which last erupted only 7,200 years ago.[20]The volcanoes generally get younger as one moves from the coast to the interior. These volcanoes are thought to have formed as a result of the North American Plate sliding westward over a small hotspot, called the Anahim hotspot.[20] The hotspot is considered similar to the one feeding the Hawaiian Islands.[20] The belt is defined by three large shield volcanoes (Rainbow,Ilgachuz and the Itcha Ranges) and 37 Quaternary basalt centers.
Eruptions of basaltic to rhyolitic volcanoes and hypabyssal rocks of the Alert Bay Volcanic Belt in northern Vancouver Island are probably linked with the subducted margin flanked by the Explorerand Juan de Fuca plates at the Cascadia subduction zone. It appears to have been active during the Pliocene and Pleistocene time. However, no Holocene eruptions are known, and volcanic activity in the belt has likely ceased.
[edit]Russia
The Kamchatka Peninsula in the Russian Far East is one of the most various and active volcanic areas in the world,[21] with an area of 472,300 km². It lies between the Pacific Ocean to the east and the Okhotsk Sea to the west. Immediately offshore along the Pacific coast of the peninsula runs the 10,500 meter deep Kuril-Kamchatka Trench. This is where rapid subduction of the Pacific Plate fuels the intense volcanism. Almost all types of volcanic activity are present, from stratovolcanoes and shield volcanoes to Hawaiian-style fissure eruptions.[21]
There are over 30 active volcanoes and hundreds of dormant and extinct volcanoes in two major volcanic belts. The most recent activity takes place in the eastern belt,[21] starting in the north at the Shiveluch volcanic complex, which lies at the junction of the Aleutian and Kamchatka volcanic arcs. Just to the south is the famous Klyuchi volcanic group, comprising the twin volcanic cones of Kliuchevskoi and Kamen, the huge volcanic complexes ofTolbachik and Ushkovsky, and a number of other large stratovolcanoes. The only active volcano in the central belt is found west of here, the huge remoteIchinsky. Farther south, the eastern belt continues to the southern slope of Kamchatka, topped by loads of stratovolcanoes.
[edit]Japan
See also: 2011 Japanese nuclear accidents
Ten percent of the world's active volcanoes are found in Japan, which lies in a zone of extreme crustal instability. They are formed by subduction of the Pacific Plate and the Philippine Sea Plate. As many as 1,500 earthquakes are recorded yearly, and magnitudes of four to six on the Richter scale are not uncommon. Minor tremors occur almost daily in one part of the country or another, causing slight shaking of buildings. Major earthquakes occur infrequently; the most famous in the twentieth century were: the Great Kantō earthquake of 1923, in which 130,000 people died; and the Great Hanshin earthquake of 17 January 1995, in which 6,434 people died. On March 11, 2011 a magnitude 8.9 Earthquake hit Japan, the country's biggest ever and the fifth largest on record, according to US Geological Survey data.[22] Undersea earthquakes also expose the Japanese coastline to danger from tsunamis.
Mount Bandai, one of Japan's most noted volcanoes, rises above the north shore of Lake Inawashiro. Mount Bandai is formed of several overlappingstratovolcanoes, the largest of which is O-Bandai forming a complex volcano. O-Bandai volcano was constructed within a horseshoe-shaped caldera that formed about 40,000 years when an earlier volcano collapsed, forming the Okinajima debris avalanche, which traveled to the southwest and was accompanied by a plinian eruption. Four major phreatic eruptions have occurred during the past 5,000 years, two of them in historical time, in 806 and 1888. Seen from the south, Bandai presents a conical profile, but much of the north side of the volcano is missing as a result of the collapse of Ko-Bandai volcano during the 1888 eruption, in which a debris avalanche buried several villages and formed several large lakes.
Nearly a century ago, the north flank of Mount Bandai collapsed during an eruption quite similar to the May 18, 1980 eruption of Mount St. Helens. After a week of seismic activity, a large earthquake on July 15, 1888, was followed by a tremendous noise and a large explosion. Eyewitnesses heard about 15 to 20 additional explosions and observed that the last one was projected almost horizontally to the north.
Mount Fuji is Japan's highest and most noted volcano. The modern postglacial stratovolcano is constructed above a group of overlapping volcanoes, remnants of which form irregularities on Fuji's profile. Growth of the younger Mount Fuji began with a period of voluminous lava flows from 11,000 to 8,000 years ago, accounting for four-fifths of the volume of the younger Mount Fuji. Minor explosive eruptions dominated activity from 8,000 to 4,500 years ago, with another period of major lava flows occurring from 4,500 to 3,000 years ago. Subsequently, intermittent major explosive eruptions occurred, with subordinate lava flows and small pyroclastic flows. Summit eruptions dominated from 3,000 to 2,000 years ago, after which flank vents were active. The extensive basaltic lava flows from the summit and some of the more than 100 flank cones and vents blocked drainages against the Tertiary Misaka Mountains on the north side of the volcano, forming the Fuji Five Lakes. The last eruption of this dominantly basaltic volcano in 1707 ejected andesitic pumice and formed a large new crater on the east flank. Scientists are saying that there may be some minor volcanic activity in the next few years.
[edit]Philippines
The 1991 eruption of Mount Pinatubo is the world's second largest terrestrial eruption of the 20th century. Successful predictions of the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives, but as the surrounding areas were severely damaged by pyroclastic flows, ash deposits, and later, lahars caused by rainwater remobilising earlier volcanic deposits, thousands of houses were destroyed.
Mayon Volcano is the Philippines' most active volcano. The volcano has steep upper slopes that average 35–40 degrees and is capped by a small summit crater. The historical eruptions of this basaltic-andesitic volcano dates back to 1616 and ranges from Strombolian to basaltic Plinian eruptions. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flowsand mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas.
Taal Volcano has had 33 recorded eruptions since 1572. A devastating eruption occurred in 1911, which claimed more than a thousand lives. The deposits of that eruption consisted of a yellowish, fairly decomposed (non-juvenile) tephra with a high sulfur content. The most recent period of activity lasted from 1965 to 1977, and was characterized by the interaction of magma with the lake water, which produced violent phreatic explosions. Although the volcano has been dormant since 1977, it has shown signs of unrest since 1991, with strong seismic activity and ground fracturing events, as well as the formation of small mud geysers on parts of the island.
Canlaon is the most active volcano in central Philippines and has erupted 25 times since 1866. Eruptions are typically phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano. On August 10, 1996, Kanlaon erupted without warning, killing British student Julian Green and Filipinos Noel Tragico and Neil Perez, who were among 24 mountainclimbers who were trapped near the summit.
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