Report on Masaya (Nicaragua) — July 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 7 (July 1997)
Managing Editor: Richard Wunderman.
Masaya (Nicaragua) Minor morphologic changes and fluctuating incandescence in May
Please cite this report as:
Global Volcanism Program, 1997. Report on Masaya (Nicaragua). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 22:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199707-344100.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
"On 25 May, observers saw that the small active vent had grown by 30 m and had ceased to be incandescent. Large volumes of gas were still escaping and forming plumes that blew to the W. Masaya park guards reported a resumption of incandescence on 3 June. During the previous day, there was little wind and high humidity, conditions which allowed the gas to produce a sustained vertical column above the crater."
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 Nindirí 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: Benjamin van Wyk de Vries, Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom (URL: http://www.open.ac.uk/science/environment-earth-ecosystems/).