Report on Masaya (Nicaragua) — October 1993

Bulletin of the Global Volcanism Network, vol. 18, no. 10 (October 1993)
Managing Editor: Edward Venzke.

Masaya (Nicaragua) Incandescent hole in lava lake remains active

Please cite this report as:

Global Volcanism Program, 1993. Report on Masaya (Nicaragua). In: Venzke, E (ed.), Bulletin of the Global Volcanism Network, 18:10. Smithsonian Institution.

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11.984°N, 86.161°W; summit elev. 635 m

All times are local (unless otherwise noted)

Scientists approached the incandescent window of the lava lake in Santiago's inner crater on 19 October to sample lava ejected during an episode of increased explosive activity at the beginning of October. The window was 15 m in diameter and 50 m deep with lava splashing every 10-15 seconds. Bright yellow incandescence was reported on 31 August and was first observed on 16 June of this year (BGVN 18:06, 18:07, and 18:09).

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of NindirĂ­ and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.

Information Contacts: Alain Creusot, Instituto Nicaraguense de Energía, Managua, Nicaragua.