Contents

07 April 1989
Vol 244, Issue 4900

About The Cover

Vertical section through 15-cm-high sand boil caused by liquefaction during the 24 November 1987 Superstition Hills, California, earthquake. Alternating layers of fine (dark) and coarse (light) sediment indicate that discharge rate through the feeder dike in the reddish-brown soil beneath the sand boil was variable. See page 56. [Photograph by T. C. Hanks, U.S. Geological Survey, Menlo Park, CA 94025]