MadSci Network: Earth Sciences

Re: Could a meteor have caused the earths landmass to split into continents?

Date: Mon Aug 13 10:30:28 2001
Posted By: David Smith, Faculty Geology, Environmental Science
Area of science: Earth Sciences
ID: 997093615.Es

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:

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:

Another site shows experimentally created impacts and talks about what they 
imply for the Chicxulub impact:

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:

David Smith
Geology and Environmental Science, La Salle University, Philadelphia, PA

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