Geologic Background:
Cosiguina is a low basaltic-to-andesitic
composition volcano that is isolated from other volcanoes
in the Nicaraguan volcanic chain and forms a large
peninsula at the western tip of the country along the
Gulf of Fonseca. The stratovolcano has a pronounced somma
rim on the north side. A young summit cone rises 300 m
above the northern somma rim and buries the rim on other
sides. The younger cone is truncated by a large
elliptical prehistoric summit caldera, 2 x 2.4 km in
diameter and 500 m deep with a lake at its bottom. Lava
flows predominate in the caldera walls, although lahar
and pyroclastic-flow deposits surround the volcano.
Historic Activity:
- Cosiguina was the source of a brief but powerful
explosive eruption in 1835, Nicaragua's largest during
historical time. Ash fell as far away as Mexico, Costa
Rica, and Jamaica, and pyroclastic flows reached the Gulf
of Fonseca.
- Additional eruptions in 1852 and 1859.
Recent Activity:
Data Sources
- Smithsonian's SEAN Bulletin (V. 5, No. 12)
- Global Volcanism Network (V. 24, No. 4).
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