Previously unobserved fumarolic activity on the SE spur of Casita (at sites 150 m and 0.5-1 km below the communications complex on the summit) was noticed on 8 June. Area residents report that the activity has been present for some time. Emissions appear to originate from a N-S fissure (figure 1). Casita was last reported active in the l6th century.

Figure 1. Oblique sketch of Casita, its fumaroles, and neighboring volcanic features, 8 June 1989. Courtesy of B. van Wyk de Vries and O. Castellón.

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: B. van Wyk de Vries and O. Castellón, INETER, Managua.