Geology may have driven species extinction

Biodiversity booms and busts every 60 million years could be tied to a geological cycle of periodic uplifting of the world's continents, U.S. researchers say. Study leader Adrian Melott at the University of Kansas says periodic increases in the amount of the isotope strontium-87 found in marine fossils corresponds to previously discovered low points in marine biodiversity in the fossil record roughly every 60 million years. A periodic uplifting of the continents, Melott said, is the most likely explanation for the increase in the isotope in marine fossils, since it leads to erosion of landmasses that would release the isotope into the marine environment. The massive continental uplifts suggested by the strontium data would reduce sea depth along the continental shelf where most sea animals live, researchers said. That loss of habitat due to shallow water, Melott and collaborators report, could be the reason for the periodic mass extinctions and periodic decline in diversity found in the marine fossil record. "What we're seeing could be evidence of a 'pulse of the earth' phenomenon," Melott said. "There are some theoretical works which suggest that convection of mantle plumes, rather like a lava lamp, should be coordinated in periodic waves." The result of this convection deep inside the earth, he said, could be a rhythmic throbbing that pushes the continents up and down. The research is published in the March issue of The Journal of Geology.