Sunday, July 19, 2009

Pacific Ring of Fire Region

"The Pacific Ring of Fire (or sometimes just Ring of Fire) is an area where large numbers of earthquakes and volcaniceruptions occur in the basin of the Pacific Ocean. In a 40,000 km horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements. The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and dormant volcanoes. It is sometimes called the circum-Pacific belt or the circum-Pacific seismic belt.
About 90% of the world's earthquakes and 80% of the world's largest earthquakes occur along the Ring of Fire. The next most seismic region (5–6% of earthquakes and 17% of the world's largest earthquakes) is the Alpide belt, which extends from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic. The Mid-Atlantic Ridge is the third most prominent earthquake belt.
The Ring of Fire is a direct result of plate tectonics and the movement and collisions of crustal plates. The eastern section of the ring is the result of the Nazca Plate and the Cocos Plate being subducted beneath the westward moving South American Plate. A portion of the Pacific Plate along with the small Juan de Fuca Plate are being subducted beneath the North American Plate. Along the northern portion the northwestward moving Pacific plate is being subducted beneath the Aleutian Islands arc. Further west the Pacific plate is being subducted along the Kamchatka Peninsula arcs on south past Japan. The southern portion is more complex with a number of smaller tectonic plates in collision with the Pacific plate from the Mariana Islands, the Philippines, Bougainville, Tonga, and New Zealand. Indonesia lies between the Ring of Fire along the northeastern islands adjacent to and including New Guinea and the Alpide belt along the south and west from Sumatra, Java, Bali, Flores, and Timor. The famous and very active San Andreas Fault zone of California is a transform fault which offsets a portion of the East Pacific Rise under southwestern United States and Mexico. The motion of the fault generates numerous small earthquakes, at multiple times a day, most of which are too small to be felt. The active Queen Charlotte Fault on the west coast of the Queen Charlotte Islands, British Columbia, Canada, has generated three large earthquakes during the 20th century: a magnitude 7 event in 1929, a magnitude 8.1 occurred in 1949 (Canada's largest recorded earthquake) and a magnitude 7.4 in 1970." (Information provided by

Villarrica Volcano

Villarrica Volcano is part of the Pacific Ring of Fire Region. "Snow-covered Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. The volcano is also known as Rucapillán, a Mapuche word meaning "House of the Pillán". It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain along the Gastre Fault. This alignment crosses the N-S running Liquiñe-Ofqu Fault. Villarrica is one of only four volcanoes worldwide known to have an active lava lake within its crater. Villarrica's lava is basaltic-andesitic but is quite explosive despite this. Two large ignimbrite layers are visible around the volcano; the Licán Ignimbrite and later the Pucón Ignimbrite." (Information provided by

El Chichon Volcano

"El Chichón, also known as El Chichonal, is an active volcano in northwestern Chiapas, Mexico. Its only recorded eruptive activity was on March 29, April 3 and April 4, 1982, when it produced a one km-wide caldera that then filled with an acidic crater lake. The eruption killed around 2,000 people who lived near the volcano. It had high-sulphur anhydrite-bearing magma, explosive eruptions, pyroclastic flows, and surges that were devastating.
Solar radiation transmittance measured at the Mauna Loa Observatory (Hawaii), the eruption of El Chichón caused a decrease of ~16%
In 2000, the lake's water temperature increased. Also, the lake acquired a blue-green color, due to massive amounts of dissolved minerals in the acidic water, and fine, light-colored ashy sediment continually stirred up by boiling areas.
El Chichon is part of a geologic zone known as the Chiapanecan Volcanic Arc. This volcanic region is thought to be the result of the subduction of the Tehuantepec Ridge, an undersea ridge which lies on the Cocos Plate off the Pacific coast of Mexico." (Information provided by

Popcatepetl Volcano

"Popocatépetl is an active volcano and, at 5,426 m (17,802 ft), the second highest peak in Mexico after the Pico de Orizaba (5,636 m). Popocatépetl is linked to the Iztaccíhuatl volcano to the north by the high saddle known as the Paso de Cortés, and lies in the eastern half of the Trans-Mexican volcanic belt.
The name Popocatépetl comes from the Nahuatl words popōca 'it smokes' and tepētl 'mountain', thus Smoking Mountain; the name Don Goyo comes from the mountain’s association in the lore of the region with San Gregorio (St. Gregory), ‘Goyo’ being a nickname-like short form of Gregorio.

The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris avalanche deposits covering broad areas south of the volcano. The modern volcano was constructed to the south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 AD, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano.
Popocatepetl is one of the most active volcanoes in Mexico, having had more than 20 major eruptions since the arrival of the Spanish in 1519. A major eruption occurred in 1947 to begin this cycle of activity. Then, on December 21, 1994 the volcano spewed gas and ash which was carried as far as 25 km (16 mi) away by prevailing winds. The activity prompted the evacuation of nearby towns and scientists to begin monitoring for an eruption. In December 2000, tens of thousands of people were evacuated by the government based on the warnings of scientists. The volcano then made its largest display in 1200 years." (Information provided by

Mount St. Helens

"Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It is 96 miles (154 km) south of Seattle and 53 miles (85 km) northeast of Portland, Oregon. Mount St. Helens takes its English name from the British diplomat Lord St Helens, a friend of explorer George Vancouver who made a survey of the area in the late 18th century. The volcano is located in the Cascade Range and is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire that includes over 160 active volcanoes. This volcano is well known for its ash explosions and pyroclastic flows.
Mount St. Helens is most famous for its catastrophic eruption on May 18, 1980, at 8:32am PDT which was the deadliest and most economically destructive volcanic event in the history of the United States. Fifty-seven people were killed; 250 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (298 km) of highway were destroyed. The eruption caused a massive debris avalanche, reducing the elevation of the mountain's summit from 9,677 feet (2,950 m) to 8,365 feet (2,550 m) and replacing it with a 1 mile (1.6 km) wide horseshoe-shaped crater. The debris avalanche was up to 0.7 cubic miles (2.9 km3) in volume. The Mount St. Helens National Volcanic Monument was created to preserve the volcano and allow for its aftermath to be scientifically studied.
As with most other volcanoes in the Cascade Range, Mount St. Helens is a large eruptive cone consisting of lava rock interlayered with ash, pumice, and other deposits. The mountain includes layers of basalt and andesite through which several domes of dacite lava have erupted. The largest of the dacite domes formed the previous summit, and off its northern flank sat the smaller Goat Rocks dome. Both were destroyed in the 1980 eruption.
Shaken by an earthquake measuring 5.1 on the Richter scale, the north face of this tall symmetrical mountain collapsed in a massive rock debris avalanche. Nearly 230 square miles (600 km2) of forest was blown down or buried beneath volcanic deposits. At the same time a mushroom-shaped column of ash rose thousands of feet skyward and drifted downwind, turning day into night as dark, gray ash fell over eastern Washington and beyond. The eruption lasted 9 hours, but Mount St. Helens and the surrounding landscape were dramatically changed within moments." (Information provided by

Mount Rainer

"Mount Rainier is an active stratovolcano (also known as a composite volcano) in Pierce County, Washington, located 54 miles (87 km) southeast of Seattle. It towers over the Cascade Range as the most prominent mountain in the contiguous United States and Cascade Volcanic Arc at 14,411 feet (4,392 m).
The mountain and the surrounding area are protected within Mount Rainier National Park. With 26 major glaciers and 35 square miles (91 km2) of permanent snowfields and glaciers, Mount Rainier is the most heavily glaciated peak in the lower 48 states. The summit is topped by two volcanic craters, each over 1,000 feet (300 m) in diameter with the larger east crater overlapping the west crater. Geothermal heat from the volcano keeps areas of both crater rims free of snow and ice, and has formed the world's largest volcanic glacier cave network within the ice-filled craters. A small crater lake about 130 by 30 feet (40 m × 9.1 m) in size and 16 feet (5 m) deep, the highest in North America with a surface elevation of 14,203 feet (4,329 m), occupies the lowest portion of the west crater below more than 100 feet (30 m) of ice and is accessible only via the caves." (Information provided by

Mount Redoubt

"Mount Redoubt, or Redoubt Volcano, is an active and currently erupting stratovolcano in the largely volcanic Aleutian Range of the U.S. state of Alaska. It is located in the Chigmit Mountains (a subrange of the Aleutians), west of Cook Inlet, in the Kenai Peninsula Borough about 180 km (110 miles) southwest of Anchorage. The Alaska Volcano Observatory currently rates Redoubt as Aviation Alert Level Orange and Volcano Alert Level Watch. Mount Redoubt rises 9,000 feet (2,700 m) above the surrounding valleys to the north, south, and southeast in little over 5 miles (8 km); it is also the third highest within the range, with nearby Mount Torbert, at 11,413 feet, being the highest in the range and Mount Spurr at 11,070 feet being the second highest.
Active for millennia, Mount Redoubt has erupted five times since 1900: in 1902, 1922, 1966, 1989 and 2009. The eruption in 1989 spewed volcanic ash to a height of 14,000 m (45,000 ft) and managed to catch KLM Royal Dutch Airlines flight 867, a Boeing 747 aircraft, in its plume (the flight landed safely at Anchorage). The ash covered an area of about 20,000 km² (7,700 sq. miles). The 1989 eruption is also notable for being the first ever volcanic eruption to be successfully predicted by the method of long-period seismic events developed by Swiss/American volcanologist Bernard Chouet." (Information provided by

Kliuchevskoi Volcano-Russia

"Kliuchevskoi is one of the most active volcanoes of the Kamchatka Peninsula in Far Eastern Russia. The volcano has had more than 80 eruptions since 1697. On September 15, 1994, gas and ash shot out of the crater, creating a column 2 km high. Over the next two weeks the eruption continued, and on 1 October a giant eruption occurred. A cloud of ash rose 15-20 km above the volcano. A picture taken by a weather satellite showed that the ash cloud extended 565 km to the SE, and that it was moving at about 140 km/hr (~85 mile/hr)! While ash was being blown out the top of the volcano, new rivers of lava flowed down its flanks. During the next three days the eruption stopped, and only steam rose above the crater." (Information provided by

Mount Tolbachik

"The massive Tolbachik basaltic volcano is located at the southern end of the dominantly andesitic Kliuchevskaya volcano group. The Tolbachik massif is composed of two overlapping, but morphologically dissimilar volcanoes. The flat-topped Plosky Tolbachik shield volcano with its nested Holocene Hawaiian-type calderas up to 3 km in diameter is located east of the older and higher sharp-topped Ostry Tolbachik stratovolcano. The summit caldera at Plosky Tolbachik was formed in association with major lava effusion about 6500 years ago and simultaneously with a major southward-directed sector collapse of Ostry Tolbachik volcano. Lengthy rift zones extending NE and SSW of the volcano have erupted voluminous basaltic lava flows during the Holocene, with activity during the past two thousand years being confined to the narrow axial zone of the rifts. The 1975-76 eruption originating from the SSW-flank fissure system and the summit was the largest historical basaltic eruption in Kamchatka." (Information provided by

Mount Fuji

"Mount Fuji (富士山, Fuji-san) is the highest mountain in Japan at 3,776 m (12,388 ft). Along with Mount Tate and Mount Haku, it is one of Japan's Three Holy Mountains. An active volcano that last erupted in 1707–08, Mount Fuji straddles the boundary of Shizuoka and Yamanashi prefectures just west of Tokyo, from which it can be seen on a clear day.
The climate is very cold due to the altitude and the cone is covered by snow for several months of the year. The lowest recorded temperature is −38.0 °C while on June 2008 the highest temperature was recorded at 17.8 °C.
Mount Fuji is a 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.
Mount Fuji is located at the point where the Amurian Plate, the Okhotsk Plate, and the Philippine Sea Plate meet. Those plates form the western part of Japan, the eastern part of Japan, and the Izu Peninsula respectively." (Information provided by

Mount Pinatubo

"Mount Pinatubo is an active stratovolcano located on the island of Luzon, at the intersection of the borders of the Philippine provinces of Zambales, Tarlac, and Pampanga. It is located in the Cabusilan Mountain range separating the west coast of Luzon from the central plains, and is 42 km (26 mi) west of the dormant and more prominent Mount Arayat, occasionally mistaken for Pinatubo.
The volcano's ultra-Plinian eruption in June 1991 produced the second largest terrestrial eruption of the 20th century (after the 1912 eruption of Novarupta) and the largest eruption in living memory. The colossal 1991 eruption had a Volcanic Explosivity Index (VEI) of 6, and came some 450–500 years after the volcano's last known eruptive activity (estimated as VEI 5, the level of the 1980 eruption of Mount St. Helens), and some 1000 years after previous VEI 6 eruptive activity. 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 surrounding areas were severely damaged by pyroclastic flows, ash deposits, and later by lahars caused by rainwater remobilizing earlier volcanic deposits: thousands of houses and other buildings were destroyed.
The effects of the eruption were felt worldwide. It ejected roughly 10 billion metric tonnes (10 cubic kilometres) of magma, and 20 million tons of SO2, bringing vast quantities of minerals and metals to the surface environment." (Information provided by

Mayon Volcano

"Mayon Volcano, also known as Mount Mayon, is an active stratovolcano in the province of Albay, in the Bicol Region, on the island of Luzon, in the Philippines.
Renowned as the "Perfect Cone" because of its almost perfectly conical shape, Mayon is situated 15 kilometres northwest of Legazpi City.
Mayon is an active stratovolcano. The current cone was formed through pyroclastic and lava flows from past eruptions. Mayon is the most active of the active volcanoes in the Philippines, having erupted over 48 times in the past 400 years." (Information was provided by

Krakatau Volcano Island

Krakatoa (Indonesian: Krakatau), also spelled Krakatau, is a volcanic island made of lava in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island (also called Rakata), and the volcano as a whole.
The best-known eruption of Krakatoa culminated in a series of massive explosions on August 26–27, 1883, which was among the most violent volcanic events in modern and recorded history. With a Volcanic Explosivity Index (VEI) of 6, the eruption was equivalent to 200 megatons (MT) of TNT—about 13,000 times the nuclear yield of the Little Boy bomb (13 to 16 kT) that devastated Hiroshim, Japan during World War II and four times the yield of the Tsar Bomba (50 MT), the largest nuclear device ever detonated. (Information provided by

Kelut Volcano

Kelud (Klut, Cloot, Kloet, Kloete or Kelut) is a volcano located in East Java on Java in Indonesia. Like many Indonesian volcanoes and others on the Pacific Ring of Fire, Kelud is known for large explosive eruptions throughout its history. More than 30 eruptions have occurred since 1000 A.D.
On May 19, 1919, an eruption at Kelud killed an estimated 5,000 people, mostly through hot mudflows (also known as "lahar"). More recent eruptions in 1951, 1966, and 1990 have altogether killed another 250 people. Following the 1966 eruption, the Ampera Tunnel was built on the southwestern side of the crater to drain the crater lake and thus reduce the lahar hazard. (Information provided by

Mount Tambora

Mount Tambora (or Tomboro) is an active stratovolcano, also known as a composite volcano, on Sumbawa island, Indonesia. Sumbawa is flanked both to the north and south by oceanic crust, and Tambora was formed by the active subduction zones beneath it. This raised Mount Tambora as high as 4,300 m (14,000 ft), making it one of the tallest peaks in the Indonesian archipelago, and drained off a large magma chamber inside the mountain. It took centuries to refill the magma chamber, its volcanic activity reaching its peak in April 1815
Tambora erupted in 1815 with a rating of seven on the Volcanic Explosivity Index, making it the largest eruption since the Lake Taupo eruption in about 180 AD. It was the largest volcanic eruption in recorded history. The explosion was heard on Sumatra island (more than 2,000 km (1,200 mi) away). Heavy volcanic ash falls were observed as far away as Borneo, Sulawesi, Java and Maluku islands.

Rangitoto Volcano Island

Rangitoto was formed by a series of eruptions between 600 and 700 years ago. Scientists are in dispute about the length of the eruptions, which are thought to have lasted (with interruptions) for 10 to 200 years. In any case, the 2.3 cubic kilometres of material that erupted from the volcano was about equal to the combined mass produced by all the previous eruptions in the Auckland Volcanic Field, which were spread over more than 100,000 years.
The volcano is not expected to become active again, although future eruptions are likely within the volcanic field. Subsiding matter during the cooling process has left a moat-like ring around the crater summit, which may be viewed from a path which goes right round the rim and up to the highest point. (Information provided by

Mount Ruapehu, New Zealand

Mount Ruapehu, or just Ruapehu, is an active stratovolcano at the southern end of the Taupo Volcanic Zone in New Zealand. It is 23 kilometres northeast of Ohakune and 40 kilometres southwest of the southern shore of Lake Taupo, within Tongariro National Park. The North Island's major skifields and only glaciers are on its slopes.
Ruapehu is one of the world's most active volcanoes and the largest active volcano in New Zealand. It is the highest point in the North Island and includes three major peaks: Tahurangi (2,797 m), Te Heuheu (2,755 m) and Paretetaitonga (2,751 m). The deep, active crater is between the peaks and fills with a crater lake between major eruptions. (Information provided by

Mount Erebus Antarctica

Mount Erebus in Antarctica is the southernmost historically active volcano on Earth. With a summit elevation of 3,794 meters (12,448 ft), it is located on Ross Island. Mount Erebus is currently the most active volcano in Antarctica. The summit contains a persistent convecting phonolitic lava lake, one of a very few long-lasting lava lakes on Earth. Mount Erebus is classified as a polygenetic stratovolcano. (Information from

Friday, June 12, 2009