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Click on the links below to view animations created specifically for Earth: Portrait of a Planet.
Animations require Macromedia's Flash Plug-in.
Volcanic Neck at Shiprock
At this ancient volcano at Shiprock, New Mexico, ash and lava flows have eroded away, leaving a “volcanic neck”. Large dikes radiated outward from the center, like spokes of a wheel. The softer rocks that once surrounded the dikes have eroded away, leaving a wall-like remnant of the dike exposed. Shiprock was once in the interior of a volcano or below a volcano. |
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Antarctic Sill
This dark sill, exposed on a cliff in Antarctica, is basalt; the white rock is sandstone. A geologist’s sketch shows the cliff face as viewed face on. |
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Pluton at Torres del Paines
Torres del Paines is a spectacular group of mountains in southern Chile. The light rock is a granite pluton, and the dark rock is the remains of the country rock into which the pluton intruded. A screen of country rock (in the lower half) hides the front of the pluton. A geologist’s sketch labels the two major rock units. |
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Formation of Igneous Rocks at Mid-Ocean Ridges
Igneous magmas form at mid-ocean ridges because of decompression melting of the rising asthenosphere. As you saw in Chapter 4, magma rises into the crust and pools in a magma chamber during sea-floor spreading. Some cools slowly along the margins of the magma chamber to form massive gabbro, while some intrudes upward to fill vertical cracks that appear as the newly formed crust splits apart. Magma that cools in the cracks creates basalt dikes, and magma that makes it to the sea floor extrudes as pillow basalt. |
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Additional Resources
The abundance of geology-related websites speaks to the active and exciting nature of this field. In the space below we link to external websites that explore topics covered in this chapter.
These links are selected carefully and updated regularly; however, their contents may change over time. Please click here to report a bad or missing link.
» Search for specific topics » Browse the Link Library
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Hot Spot Volcanism
5/23/2005 MantlePlumes.org |
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Links to articles, illustrations, and discussions of mantle plumes and hot-spot volcanism. |
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Large Igneous Provinces (LIPs)
5/23/2005 International Association of Volcanology |
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This page offers resources concerning large igneous provinces (LIPs); includes maps and definitions. |
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Photo glossary of volcano terms
5/23/2005 U.S.G.S. |
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A list of vocabulary used to describe volcanoes and the products of volcanic eruptions. Clicking on a term provides a definition and a photograph. |
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Volcano World
5/23/2005 University of North Dakota |
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A list of current volcanoes, maps showing their locations, photos of eruptions, and various activities related to volcanoes. |
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