A team from Dartmouth College visited the volcano from 12 to 30 March . . . . The level of activity was very low and static. There was no regular activity, and no big changes have occurred. Every few days there was a little shudder of superficial tremor in the volcano, and perhaps a short, spasmodic earthquake, but nothing very important. There was nothing out of character with the gradual buildup of activity that has been observed over the past couple of months.

On 9-10 March an eruption of ash drifted into the town of Chinandega, and there was a small ash eruption, mainly confined to the crater area, on 16 March at 1130. The team collected some sand from the latter eruption. Because the gases were too thick and heavy the crater could not be entered. When viewed from the air, sulfur coated everything in the crater to the point where it was actually overlapping the rim on the leeward side. The team did not get the impression that any inordinate activity was imminent at San Cristóbal.

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.

Information Contacts: Dept. of Earth Sciences, Dartmouth College.