Geologic Background:
Socorro Island, part of the Revillagigedo
Islands, is located about 716 km west of Manzanillo,
Colima, and 480 km south of the tip of Baja California.
Tectonically, it is located on the west flank of the East
Pacific Rise, south of the Riverra Fracture Zone. Socorro
Island is formed by a large shield volcano that contains
a summit caldera largely filled by post-caldera tephra
and domes. The island is a compositionally diverse
volcanic complex that rises about 4000 m from the
surrounding ocean floor. Based on recent 40Ar/39Ar
dating, ages range from 540 to 15 Ka, but the youngest
reported age, from a lava flow on the south side of the
island, probably does not represent the youngest unit.
The summit fumarole area of Everman volcano on Socorro
Island consists of summit lava dome complex, composed of
abundant obsidian and other less vitric lavas. Fumaroles
occur around several of the summit domes.
Historic Activity:
- The most recent volcanic activity in the islands was
in 1952 at Barcena volcano on San Benedicto Island, about
50 km north of Socorro. Eruptions have been reported from
Socorro in 1848, 1896, 1905, and May 22, 1951, but there
are no clear details about the eruptions or their
effects.
Recent Activity:
- An underwater eruption offshore of Socorro Island was
first observed on Jan. 29, 1993, 10 days after seismic
precursors were first recorded. Eruptive activity was
observed from the boat "Mystique". As they approached a
steam column, they observed hot, dark-colored rocks about
1-3 m across breaking the surface in an area of about 50
sq. m. No explosive activity or volcanic plume was
observed. Depending on vesicularity, blocks either sank
or floated. Floating rocks covered an area of about 6000
sq m by Jan. 31. Soundings gave depths of 138 to 149 m in
an area where large number of gas bubbles were being
generated.
Data Sources:
- Global Volcanism Network (V. 18, No. 1 and V. 21, No.
3).
|