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America's Volcanic Past

"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
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Map, Location of Alabama

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
  • Alabama Regions
  • Alabama's Volcanic Rocks
  • Granitic Plutons
  • University of Alabama



Excerpt from:

Alabama Regions

The Interior Plains:2
The Interior Plains is a vast region that spreads across the stable core (craton) of North America. This area had formed when several small continents collided and welded together well over a billion years ago, during the Precambrian. Precambrian metamorphic and igneous rocks now form the basement of the Interior Plains and make up the stable nucleus of North America. With the exception of the Black Hills of South Dakota, the entire region has low relief, reflecting more than 500 million years of relative tectonic stability.

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.


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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05/20/03, Lyn Topinka