19 July 1991
Vol 253, Issue 5017

About The Cover

Submarine fallout deposits in the Mio-Pliocene Shirahama Group, 500 meters west of the Senjojiki, near the southern tip of the Izu Peninsula, Japan. Pieces of pumice (light colored) are an average of six to seven times as large as codeposited rock fragments (dark colored); this ratio suggests that the deposits are formed by fallout of these particles from a submarine eruption column. Dark layers mark zones of reworking where ocean currents preferentially transported the lightweight pumice. See page 275. [Photograph by R. S. Fiske, Smithsonian Institution]