INETER reported that seismic tremor at San Cristóbal increased at 0340 on 17 January; RSAM values increased from a baseline of 70 to 460 units. Twelve gas emissions were observed between 1259 and 1315, and RSAM climbed to 649 units. A report at 1700 noted that RSAM values decreased to 100 and no additional gas emissions were observed. The next day, 18 January, RSAM values fluctuated between 90 and 190 units.

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.

Source: Instituto Nicaragüense de Estudios Territoriales (INETER)