The 1957 explosive eruption on Iwo Jima, Volcano Islands

Abstract

An explosive eruption occurred without warning on March 28, 1957, near the center of Iwo Jima, a small volcanic island midway between Guam and Tokyo, Japan. The eruption of steam, volcanic sand, and volcanic sandstone and conglomerate blocks began suddenly at 11:55 A.M. local time, continued for 65 min., and ended abruptly. Coarse ejecta were thrown as high as 150 ft.; dust and steam rose to heights of 200 to 300 ft. No juvenile material was ejected. An elliptical crater 90 to 110 ft. in diameter and 45 ft. deep resulted. Deposits were concentrated to the western (lee) side where they ranged in thickness from 22 ft. near the crater to less than one inch 300 ft. to the W. About 50 min. after the eruption a second crater formed by collapse 75 ft. NW. of the eruption crater. The circular collapse crater was 115 ft. in diameter and 55 ft. deep. Many ground cracks and small faults with displacements up to 8 in. were formed nearby during and following the eruption. Steam and other gases issued from the craters, faults, and cracks following the eruption, and some sublimates were deposited. No significant change of fumarolic activity was noted on other parts of the island before, during, or after the eruption. The eruption resulted from the sudden release of an underground accumulation of steam under high pressure beneath artificial fill adjacent to an abandoned airfield. The eruption does not seem to indicate an increase in volcanic activity on Iwo Jima.