INETER reported that at 1209 on 12 January a large explosion at Momotombo ejected incandescent material onto the flanks and generated an ash plume that rose 4 km above the crater. Tephra was deposited on the E, NE, N, and NW flanks. Ash plumes drifted downwind and caused ashfall in the communities of Flor de Piedra, La Concha (40 SSE), Amatistán, Guacucal (40 km N), La Palma, Puerto Momotombo (10 km WSW), La Sabaneta, Mira Lago, Asentamiento Miramar, Pancasán, René Linarte, Raúl Cabezas, and Betania. At around 0500 on 15 January strong volcanic tremor was accompanied by small explosions in the crater; ejected ash and incandescent tephra were deposited on the W flank. Seismicity decreased during 16-17 January.

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.

Source: Instituto Nicaragüense de Estudios Territoriales (INETER)