Report on Masaya (Nicaragua) — January 1988
Scientific Event Alert Network Bulletin, vol. 13, no. 1 (January 1988)
Managing Editor: Lindsay McClelland.
Masaya (Nicaragua) Vigorous degassing continues; small tephra eruptions and glow
Please cite this report as:
Global Volcanism Program, 1988. Report on Masaya (Nicaragua). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 13:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198801-344100.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
When geologists visited the volcano on 25 December 1987 and 6 and 18 January 1988, two new, growing vents were visible (figure 5). The N vent was the hottest (table 1) and most active, emitting the majority of gases. By 18 January, the inner crater occupied half of Santiago's floor, while Santiago expanded westwards by collapse of the floor of neighboring Nindirí Crater. The NW side of Nindirí also seemed to be sagging along boundary faults. Gas output varied from vigorous (similar to 1985-86) to very little, perhaps because of periodic blockage of the two vents by landslides and rockfalls. One large gas burst was preceded by a loud roar and slightly raised temperatures.
|Figure 5. Sketch map of the craters of the Masaya complex as of 18 January 1988, showing the locations of temperature measurements in table 1.|
|25 Dec 1987||35-40°||54.6°||66-125°||100.5°||80°|
|06 Jan 1988||40°||--||110°||121°||--|
|18 Jan 1988||36°||--||161°||160°||--|
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: B. van Wyk de Vries, H. Rymer, and G. Brown, Open Univ; P. Hradecky and H. Taleno, INETER.