According to a news report, at 0518 on 18 August SINAPRED received reports of ash fall in some communities near San Cristóbal, including La Grecia, and the municipalities of El Viejo (18 km WSW) and El Realejo (25 km SW). Based on analysis of satellite images and information from INETER, the Washington VAAC reported that a small ash puff from the volcano rose 300 m above the crater rim and drifted NW. Later that day a gas emission possibly containing ash rose 300 m and drifted W. An ash plume identified in satellite images extended as far as 265 km W. Seismicity was elevated. Steam-and-gas emissions continued through the rest of the day.

Geological Summary. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Sources: Washington Volcanic Ash Advisory Center (VAAC), El 19 Digital