U.S. Department of the Interior
U.S. Geological Survey
The full report is available in Adobe Acrobat® Portable Document Format (PDF). You will need Adobe Acrobat Reader®, version 5 or higher, to view or print the PDF documents. If you don't already have this free viewing software or need to upgrade your version, download Adobe Acrobat Reader®. Users with visual disabilities can visit http://access.adobe.com/ for conversion tools and information to help make PDF files accessible. The PDF files are large, and may take a long time to download. If you have trouble downloading the files, you may request a copy of the report from USGS Maps and Publications.
View or download the factsheet (256 k).
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