Volcanism
| From our studies
of plate tectonics, you already know that volcanoes form at
several types of plate boundaries. In addition, there are volcanoes
that form a considerable distance from plate boundaries; these locations
are called hot spots. Thus, volcanoes form in these settings:
1. At hot spots, above mantle plumes 2. At spreading centers or rift zones, where plates are diverging 3. Above subduction zones, where one plate goes beneath another plate (i.e., converging).
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| Visit the following website that describes hot spots and mantle plumes, and specifically the Hawaiian Islands, which formed above a hot spot:
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A very good site on hot spots and mantle plumes. Includes a good link to the Yellowstone hot spot. This site is just part of a large and very good site on volcanoes in general; clicking on the "To Volcano World" button will take you to the contents page for the general site (which we will visit later in this class) |
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Question: Based on information from the above website on hot spots, how can you determine how fast the Pacific lithospheric plate moved over the Hawaiian hot spot?
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Hawaiian Volcano Observatory: Photographs and history of eruptions on Hawaii. Information about volcanic hazards. Good links to other volcanoes. Volcano Watch is a weekly newsletter. |
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The following sites display volcanoes and volcanic eruptions at or near plate boundaries. Visit 1 of the following 2 sites:
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Current and historical information about Italy's Stromboli volcano. Very good pictures, movies of eruptions. Shows relationship between volcanic eruptions and earthquake activity. Links to other volcanoes |
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Alaska Volcano Observatory: Updates on current volcanic activity, maps (atlas), hazards, databanks, and links. Click on the "Alaskan Volcanic Atlas" to access maps and pertinent text. By clicking on the map, you can get information and photographs about individual volcanoes. |
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Question: Both Stromboli and Mount St. Helens have much steeper slopes than the volcanoes that make up the Hawaiian Islands. Stromboli and Mount St. Helens also have much more explosive eruptions than occur in Hawaii. What is the explanation for these differences?
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| View some of the information at the website below, especially that for the May 18, 1980, Mount St. Helens eruption; be sure to look at some of the photographs of the eruption:
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U. S. Geological Survey Cascades Volcano Observatory: Includes information and photographs of the classic 1980 eruption of Mount St. Helens, plus information and photographs of other volcanoes. Volcanic hazards, current volcanic activity, many links to other sources. Many maps of volcanoes and volcanic features. |
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Volcano World: This seemingly enormous site probably gives access to all information that you might ever want about volcanoes. Be sure to click on the "Current Eruption" button on the home page, and then click on several volcanoes to see photographs of eruptions. There also is a "Teaching and Learning" link that you might find useful. |
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Question: When Mount St. Helens exploded in 1980, part of the volcano was destroyed. What were other consequences of the explosion? |
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