Report on Masaya (Nicaragua) — March 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 3 (March 1981)
Managing Editor: Lindsay McClelland.
Masaya (Nicaragua) Gas emission continues unabated; pit crater enlarges
Please cite this report as:
Global Volcanism Program, 1981. Report on Masaya (Nicaragua) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 6:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198103-344100.
11.985°N, 86.165°W; summit elev. 594 m
All times are local (unless otherwise noted)
"Scientists from Dartmouth College, IRENA, and the Instituto de Investigaciones Sísmicas report the following based on their continuing cooperative observation of Nicaraguan volcanoes.
"The fourth gas emission crisis of this century continued unabated. Extensive remote measurement of SO2 output (by COSPEC) has revealed a greater variability in emission rates than had previously been recognized (several hundred to several thousand t/d). The pit crater from which the gas is emitted continued to increase slowly in diameter and was strongly elongate in the NW-SE direction. Night observation of the activity was possible and confirmed the complete absence of any incandescence in the pit where lava was visible as recently as November 1978."
Geologic Background. 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 Nindirí 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: S. Williams, R. Stoiber, Dartmouth College; D. de Jerez, IRENA; D. Fajardo B., Instituto de Investigaciones Sísmicas.