| MadSci Network: Earth Sciences |
No. Meteor and asteroid impacts cause effects that occur over very short time scales (a few seconds for the initial blast, a few years to a few decades for the climatic and other effects). Impacts don't push rocks around in big blocks, they vaporize, melt, or pulverize the rocks they affect. Continental motions, on the other hand, occur over time scales of hundreds of millions of years. For an example of impact effects, see this web site on the Chesapeake Bay impact, ~35 million years ago: http://marine.usgs.gov/fact-sheets/fs49-98/ For more examples see this page that talks about the effects of the Chicxulub impact (in the Yucatan)that ended the age of the dinosaurs: http://www.agu.org/sci_soc/sharpton.html Another site shows experimentally created impacts and talks about what they imply for the Chicxulub impact: http://www.brown.edu/Administration/News_Bureau/1996-97/96-041.html There is very clear and compelling evidence from multiple lines that the break-up of Pangea occured through the devlopment of continental rift valleys which, as they continued to widen, turned into sea-floor spreading centers (also known as mid-ocean ridges). The evidence for this process has been collected since the 1950's and would literally fill a library. It includes patterns in the magnetic and gravitational forces exerted by sea floor rocks, results from siesmic tomography (using earthquakes to give the earth a "CAT scan"), direct sampling of sea-floor rocks and direct observation of undersea geology and topography by submersibles, dredges, and deep-towed sonar, and direct measurements of plate motions. The plates are pieces of the outer solid shell of the earth that move around the surface of the earth. These plates are not merely the continents, but also include attached portions of the ocean floor. To learn about the basics of plate tectonics, you would do well to begin with the US Geological Survey's web site, where there is an electronic version of an excellent book called "This Dynamic Earth." This book might also be in your library, as may other books on plate tectonics. The online version is at: http://pubs.usgs.gov/publications/text/dynamic.html David Smith Geology and Environmental Science, La Salle University, Philadelphia, PA
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