Anatahan has no known historical eruptions. Recent activity includes a period of felt earthquakes that began on March 30, 1990. Felt earthquakes continued for two more days. An over flight revealed that the crater lake in the east part of the main caldera had become turbulent and changed color. The intensity of fumaroles had increased and the smell of rotten eggs was reported. The volcanic unrest caused the evacuation of the island's 23 residents. A field investigation found a deposit from a phreatomagmatic eruption that is younger than human occupation of the island. Overflows of hot acidic water from the lake had killed a large area of vegetation. Tilt on the flank of the volcano had not changed. Electronic distance measurements measured extension across the volcano up to about 3.5 inches (91 mm). Volcanologists returned to the island in late June. During their 2 day visit no earthquakes larger than magnitude 2.5 were recorded. Measurements of deformation revealed no significant changes since April. However, the crater lake had disappeared and was replaced by several pits and the area was vigorously steaming. Swarms of earthquakes occurred again at Anatahan in late May to early June of 1993. The islands was declared off limits. No eruption occurred. Photograph by Frank Trusdell, U.S. Geological Survey.
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Global Volcanism Network, 1990, Summary of Recent Activity: Bulletin of Volcanology, v. 52, p. 488, 491.
Global Volcanism Network, 1993, Summary of Recent Activity: Bulletin of Volcanology, v. 55, p. 536.
Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.
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