Nevado del Tolima

Geography and geology

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 kilometres (1.9 mi) 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 northern and eastern flanks, and extensive pyroclastic-flow deposits. The summit contains a funnel-shaped crater 200 to 300 metres (660 to 980 ft) 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 northeast and southeast.

Hydrology

The snow-capped Nevado del Tolima, with its almost symmetrical structure, has a radial drainage pattern in the upper part. The residual glacier on the top of the mountain feeds the rivers Totare, San Romualdo, Toche and Combeima. The latter is the main water source of the municipality of Ibagué. All these currents drain into the eastern slope of the Cordillera Central, directly into the Magdalena River.