Seismicity at Tolima was recorded in December 1987 and September-October 1988 by a telemetric station 2 km SE of the summit (figure 1). During October, as many as seven high-frequency events/day were recorded and minor fumarolic activity was observed. A 50-m-thick ice cap with an area of ~ 2 km² covers the summit.

Geologic Background. The steep-sided, glacier-clad Nevado del Tolima volcano contrasts with the broad profile of Nevado del Ruiz to the north. The andesitic-dacitic younger Tolima formed during the past 40,000 years, rising above and largely obscuring a 3-km-wide late-Pleistocene caldera. The summit consists of a cluster of late-Pleistocene to Holocene lava domes that were associated with thick block-lava flows on the N and E flanks, and extensive pyroclastic-flow deposits. The summit contains a funnel-shaped crater 200-300 m deep. Holocene activity has included explosive eruptions ranging in size from moderate to plinian. The last major eruption took place about 3600 years ago. Lava dome growth has produced block-and-ash flows that traveled primarily to the NE and SE. Minor explosive eruptions have been recorded in the 19th and 20th centuries.

Information Contacts: C. Carvajal and F. Muñoz, INGEOMINAS, Manizales.