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Geology of Volcanoes
| s Learn About the Awesome Power of Volcanoes s |
 Kilauea eruption --------- National Park Service A volcano is an opening in the earth's surface or crust, which allows molten rock, ash, and gases to escape from deep within the earth.. Volcanic activity involving the of extrision of rock forms mountains over a period of time. Volcanoes occur most often on or near crustal plates or boundaries, although certain volcanoes known as hotspot volcanoes can occur virtually anywhere. Today’s existing terrestrial volcanoes are believed to have formed when molten rock or magma welled up in the Earth’s interior pushed its way to the surface causing the volcanoes’ eruptions. | LINKS TO PAGES, DISCUSSIONS & PHOTOS FOUND ON THIS SITE ~~~~ . PHOTOS . THREADS ~~~~ Please note that the Photo and Thread Related links utilize a search of this site. Results may vary depending on keyword tags and content. | |||
| | | 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. Wikipedia | ||
| 55555 s s Undersea Tonga volcano erupts in Pacific ocean. 18/03/2009 I think this is so cool--our planet at work. A new volcano in the "Ring of Fire" rising from the depths over the subduction zone of a convergent plate boundary in the Pacific ocean. This is how stratovolcanoes like Anak Krakatau get their start! | ||||
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 click on active link : Volcano | The photo depicts Mt Vesuvius erupting and distroying the city of Pompheii.The city was considered a large city for the time, and even more cosmopolitan than Rome, which was several days’ journey from Pompeii. At around 1:00 p.m. on Aug. 24, 79 A.D., residents saw a pine tree-shaped column of smoke bursting from Vesuvius. Reaching nine miles into the sky, the column began spewing a thick pumice rain. Many residents rushed in the streets, trying to leave the city. This first phase of the eruption in fact produced 38 percent of the deaths. "Contrary to what was previously believed, a large number of deaths occurred in the first hours of the eruption. Many skeletons of those who tried to escape show fractured skulls, meaning that they died from collapsing roofs or large fragments falling from the eruptive column," By examining the density of volcanic deposits in relation to an accumulation rate of six inches per hour. | |||
| Types of Volcanoes | ||||
 Cinder cones are the simplest type of volcano. They are built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings. Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world. USGS | In 1943 a cinder cone started growing on a farm near the village of Parícutin in Mexico. Explosive eruptions caused by gas rapidly expanding and escaping from molten lava formed cinders that fell back around the vent, building up the cone to a height of 1,200 feet. The last explosive eruption left a funnel-shaped crater at the top of the cone. After the excess gases had largely dissipated, the molten rock quietly poured out on the surrounding surface of the cone and moved downslope as lava flows. This order of events--eruption, formation of cone and crater, lava flow--is a common sequence in the formation of cinder cones. | |||
 Composite volcanoesSome of the Earth's grandest mountains are composite volcanoes--sometimes called stratovolcanoes. They are typically steep-sided, symmetrical cones of large dimension built of alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs and may rise as much as 8,000 feet above their bases. Some of the most conspicuous and beautiful mountains in the world are composite volcanoes, including Mount Fuji in Japan, Mount Cotopaxi in Ecuador, Mount Shasta in California, Mount Hood in Oregon, and Mount St. Helens and Mount Rainier in Washington. USGS | | Most composite volcanoes have a crater at the summit which contains a central vent or a clustered group of vents. Lavas either flow through breaks in the crater wall or issue from fissures on the flanks of the cone. Lava, solidified within the fissures, forms dikes that act as ribs which greatly strengthen the cone. | ||
| In some eruptions, basaltic lava pours out quietly from long fissures instead of central vents and floods the surrounding countryside with lava flow upon lava flow, forming broad plateaus. Lava plateaus of this type can be seen in Iceland, southeastern Washington, eastern Oregon, and southern Idaho. Along the Snake River in Idaho, and the Columbia River in Washington and Oregon, these lava flows are beautifully exposed and measure more than a mile in total thickness. | ||||
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 Kilauea lava --------- National Park Service click on the active link | | |||
| ss | 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) | |||
Petronut |
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| Started By | Thread Subject | Replies | Last Post | ||
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| aubreyreynolds9@gmai | Plate Tectonics of the Pacific Northwest (page: 1 2 3 4 5 ... last page) | 153 | Monday, 6:22 PM EST by gromaine3 | ||
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Thread started: Oct 3 2009, 11:01 AM EDT
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I thought I would start a thread on the geology of the Pacific Northwest. It is a fascinating region with a variety of rock structures from igneous, metamorphic. to sedimentary. It was ether this or what is your favorite beer.
Bill |
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| Petronut | Possible Mud Volcanoes on Mars | 10 | Apr 1 2009, 12:22 PM EDT by DiamondProspector | ||
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Thread started: Mar 31 2009, 1:23 AM EDT
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Check out this image taken by the HiRISE camera aboard the MRO orbiting Mars. Unbelievable! Isn't it?
http://antwrp.gsfc.nasa.gov/apod/ap090330.html Eric |
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