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This article makes me wonder, Does continental drift cause occasional changes to the ocean’s currents? Would major reorganizations of ocean currents tend to cause ice ages by temporarily disrupting the flow of warm water that normally keeps the ice at bay? Would simulations of past continental positions indicate when reorganizations would have occurred?

Matt Henry
Whittier, Calif.

Computer simulations suggest that continental drift can indeed affect ocean circulation. Analyses suggest that as a result of changes in ocean circulation, the present-day climate of the North Atlantic Ocean is significantly warmer and that the Southern Hemisphere is generally cooler than they were before North and South America were joined by the Isthmus of Panama about 3 million years ago .—S. Perkins