Thrones of Vulcan
|By: Ylee, 11:17 PM GMT on July 31, 2012||+5|
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No natural phenomena on Earth has the power to shape land and climate as does volcanoes. Since the beginnings of written history, volcanoes have been feared, revered, and worshipped.
The word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn originates from Vulcan, the name of a god of fire in Roman mythology. Vulcan was the son of Jupiter and Juno.
Most volcanoes are created by plate tectonics, either by two plates pulling apart, such as those in Iceland, or by one plate going under the other, such as the volcanoes in the Pacific Oceans' Ring of Fire. A third type of volcano is formed when hot magma deep within the Earth rises to the surface and melts the crust as the tectonic plate moves over it. The Hawai'ian Islands, and the Yellowstone Caldera, are examples of this.
Volcanoes are classified as active, dormant, or extinct. An active volcano is one that has either erupted in the past 10,000 years, or has the potential to erupt. A dormant volcano is one that hasn't erupted for many millenia, but still has a potential to erupt, perhaps in the distant future. The Yellowstone Caldera is an example of this. An extinct volcano, such as Devils' Tower in Wyoming, has no chance of ever erupting.
There are several types of volcanoes. The Hawai'ian Islands, for example, are shield volcanoes. Their lava has a low silica content, which causes the lava to be runny and flow rapidly, making the volcano broad and gradually sloped. Cinder cones are usually small volcanoes that consist of ash and cinders; these volcanoes have a relatively short life span.
The type of volcano that most people think of when they think of volcanoes are stratovolcanoes. They have alternating layers of lava and ash, and are conical in shape.
1. Magma chamber
3. Conduit (pipe)
6. Branch pipe
7. Layers of ash emitted by the volcano
9. Layers of lava emitted by the volcano
11. Parasitic cone
12. Lava flow
15. Ash cloud
Mt. Fuji, Mt. Kilamanjaro, and Mt. Vesuvius, are examples of stratovolcanos. Stratovolcanoes are also generally the least stable, as they are the type most likely to have an explosive eruption.
The island of Milos used to be a stratovolcano; now what used to be its crater, is now the main bay of the island!
Milos is still volcanically active; in one of the caves on the south coast, the heat from the volcano is still great, and on the eastern shore of the harbour, there are hot sulphurous springs!
Volcanic eruptions can have an effect on climate, both regional and worldwide. Eruptions can create huge deposits of ash over a large area, choking out life. A large enough eruption can block enough of the sun's rays to cool the Earth, as in the 1815 eruption of Mount Tambora, which created global climate anomalies that became known as the "Year Without a Summer", because of the effect on North American and European weather. Agricultural crops failed and livestock died in much of the Northern Hemisphere, resulting in one of the worst famines of the 19th century. "The Great Dying", where 90% of living species died out 250 million years ago, is believed to have been caused by about a million years' worth of volcanic activity.
From the Grand Hotel Aminta, the Vesuvius Live cam!
From Johnston Ridge Observatory, the Mt. St. Helens cam!
From UTY, the Lake Shoji cam!
From Hawai'i Volcanoes National Park, the Kilauea Caldera cam!
From Denali National Park, the Sled Dog Puppies cam!
From Campi Ya Kanzi, the Live From the Savana cam!
Thanks to CENAPRED, the Tochimilco(Popocatépetl volcano) cam!
From GEONET, the Raoul Island cam!
From Milos, Greece, the Pollonia cam!
Courtesy of TroyLeslie, the feeder cam!
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