The 1990 steam explosion at Agua Shuca thermal area, El Barro, El Salvador
On 13 October 1990, a phreatic steam explosion occurred in the village of El Barro at the Agua Shuca thermal area located on the lower NW flank of the Apaneca Range.
The eruption produced a violent geyser-like fountain, lasting 10-20 minutes, of steam and mud, which killed 26 people and injured several others, and left a 15 m deep crater of 30 m diameter.
from: Smithsonian / GVP monthly reports:
An area 2-3 m in diameter of fumaroles, mud pots, and altered ground erupted violently, producing a "blast of wind, stones, and boiling water" that destroyed several small dwellings and affected an area with a 100-m radius.
The 13 October blast of steam and mud roared continuously (like a geyser) for 10-20 minutes, decreasing in intensity following the initial explosion (reported by a survivor to be around 20 seconds long). No seismic signals were recorded before or during the event by seismometers 4 and 30 km away. A portable seismometer, operated for a few days following the blast, also recorded no signals.
The 30-m-diameter, 15-m-deep crater produced by the blast was partially filled by a continuously boiling muddy lake during a 27 October visit. A sulfurous "rotten egg" smell was noted. Prior to the blast, the site was an area of steaming ground, with two small hot springs (1-2 m across) and 1 mudpot (1 m across) much smaller than the present crater.
The blast was laterally oblique to the N and its effects abruptly ended at a maximum of 130 m. Damage included downed trees and limbs, collapsed walls of buildings, and missing roofs. The massive, non-sorted deposits were clay-rich and composed of light-colored highly altered rock fragments. Deposits were thickest to the N where they ranged from 1 m on the crater rim to 30 cm at 20 m from the rim. The death toll increased to 26 after 13 people died in hospitals."