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