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Report on Masaya (Nicaragua) — September 1993


Bulletin of the Global Volcanism Network, vol. 18, no. 9 (September 1993)
Managing Editor: Edward Venzke.

Masaya (Nicaragua) Incandescence in lava lake

Please cite this report as:

Global Volcanism Program, 1993. Report on Masaya (Nicaragua) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 18:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199309-344100



11.985°N, 86.165°W; summit elev. 594 m

All times are local (unless otherwise noted)

Bright yellow incandescence was observed on the evening of 31 August through a window in the cooling lava lake at the base of Santiago Crater. Jetting sounds made by escaping gases could be heard from the crater rim. New incandescence in the bottom of the crater, reported on 16 June (BGVN 18:06 and 18:07), was the first since February-March 1989 (14:2, 4, and 6). Fumaroles located on the narrow plateau between Santiago and Masaya craters were passively degassing, and their temperatures ranged from 45-65°C.

Geological Summary. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself 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 NindirĂ­ and Masaya cones, 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 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. 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 have caused health hazards and crop damage.

Information Contacts: M. Conway and A. Macfarlane, FIU; Charles Connor, CNWA Bldg. 168, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228-0510; Oscar Leonel Urbina and C. Lugo, INETER.