Earth Sciences

Discovery of Strong Cycles in Fossil Diversity

Richard Muller and his collaborators have recently analyzed the most complete record of marine animal fossils ever compiled, the "Compendium" of Jack Sepkoski, which lists all known fossil marine animal genera back 542 million years. When the fossil diversity (number of distinct genera) is plotted, it shows a very strong 62 Myr cycle. The cycle is particularly evident in the species that endured for relatively short times, as shown in the diagram below (published in Nature, vol 434, 208-210, 10 March 2005).

Creation and Destruction of Continental Crust at Subduction Zones

Dr. Eli Silver of UC Santa Cruz will outline some of the latest research on plate tectonics. Presently, continental crust is being created in subduction zone settings (sites where tectonic plates converge) such as the Aleutians and Sumatra, due to both magmatic addition to the crust and to tectonic off-scraping. Other subduction zones (Central America, Tonga, Mariana, Peru, northern Chile, northern Japan, Kuriles) are undergoing crustal destruction through the process of subduction erosion.

Pages


Subscribe to RSS - Earth Sciences