INETER reported that at 0749 on 1 December an explosion at Momotombo generated a gas-and-ash plume that rose 1 km above the crater and drifted SW. Explosions at 0817, 0842, and 0855 generated ash plumes that rose 300 m. Gas emissions were visible the rest of the day. SINAPRED reported that during 1-2 December explosions ejected incandescent tephra and a slow-moving lava flow on the N flank was observed. Ashfall was reported in nearby communities to the W and SW, including La Concha, Los Arcos, Flor de la Piedra, La Paz Centro, and Leóin. Some families in La Paz Centro self-evacuated.

Geological Summary. Momotombo is a young stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows extend down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms an island offshore in Lake Managua. Momotombo has a long record of Strombolian eruptions, punctuated by occasional stronger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after a 10 April 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the south flank.

Sources: Instituto Nicaragüense de Estudios Territoriales (INETER), La Prensa (Nicaragua), Sistema Nacional para la Prevención, Mitigación y Atención de Desastres (SINAPRED)