America's Volcanic Past
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| "Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits." -- Excerpt from: Brantley, 1994 |
Volcanic Highlights and Features:
| [NOTE: This list is just a sample of various Alabama features or events and is by no means inclusive. All information presented here was gathered from other online websites and each excerpt is attributed back to the original source. Please use those sources in referencing any information on this webpage, and please visit those websites for more information on the Geology of Alabama.] |
Alabama:
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The Interior Plains:2
The Appalachians:2 The Appalachians are old. A look at rocks exposed in today's Appalachian mountains reveals elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks and slivers of ancient ocean floor. Strong evidence that these rocks were deformed during plate collision. The birth of the Appalachian ranges, some 480 million years ago, marks the first of several mountain building plate collisions that culminated in the construction of the supercontinent Pangea with the Appalachians near the center.
The Atlantic Plain:2 The Atlantic Plain is the flattest of the provinces. It stretches over 2,200 miles in length from Cape Cod to the Mexican border and southward another 1000 miles to the Yucatan Peninsula. The Atlantic plain slopes gently seaward from the inland highlands in a series of terraces. This gentle slope continues far into the Atlantic and Gulf of Mexico, forming the continental shelf. This region was born during the breakup of the supercontinent Pangea in the early Mesozoic Era.
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| Alabama's Volcanic Rocks |
Alabama's Granite:1
A crushed stone industry in Alabama includes
limestone, dolomite, marble,
granite, sandstone, and quartzite.
Alabama's Granite and Diabase Dikes:5
Alabama has
granitic rocks, foliated granitic rocks, and diabase dikes
| Granitic Plutons |
Granitic Plutons:7
Granitic plutonic rocks underlie large areas in the crystalline terrane of Georgia and Alabama. At present, the number of radiometric data coupled with geologic data indicate three major groups of Paleozoic granitic plutons -- a) Cambrian (and Early Ordovician?) plutons, b) Silurian-Devonian plutons, and c)
Carboniferous plutons. The Cambrian plutons appear to have been the result of island-arc or ocean-ridge volcanism, whereas the younger plutons appear to have been derived through anatexis (melting of pre-existing rock) of lower thrust sheets.
| University of Alabama |
University of Alabama:6
The University of Alabama is located in Tuscaloosa,
along the "fall line" where the Paleozoic Appalachian
Orogenic Belt plunges beneath
Mesozoic-Tertiary shelf sediments of the
Gulf Coastal Plain. Thus, the University
is within a few hours drive of a wide range of geological
environments, including: undeformed terrigenous
and carbonate sedimentary rocks of the
Black Warrior foreland basin; folded and thrusted
sedimentary rocks of the Valley and Ridge Province;
low to medium-grade meta-sedimentary, meta-volcanic,
and meta-plutonic rocks of the
Piedmont Province; high grade Precambrian Grenville
lithologies in the Pine Mountain Window;
and sediments of the Coastal Plain. Alabama is
presently a major coal and gas producer;
and has produced iron ore, gold, copper,
and tin-tantalum in the past.
Excerpts from:
1) Alabama Geological Survey Website, 2001
2) USGS/NPS Geology in the Parks Website, Geologic Provinces, 2001
3) USGS A Tapestry of Time and Terrain Website, 2002
4) University of Alabama, Department of Geography, Physiographic Regions
Map, 2002
5) Alabama Geologic Map, Geological Survey of Alabama
6) University of Alabama Website, 2002
7) Higgins, M.W., Atkins, R.L., Crawford, T.J., Crawford, III, R.F., Brooks, R., and Cook, R.B., 1988, The Structure, Stratigraphy, Tectonostratigraphy, and Evolution of the Southernmost Part of the Appalachian Orogen: U.S. Geological Survey Professional Paper 1475.
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