Hydrothermally altered rocks and lava flows are exposed in cliffs on the Irazú upper northern flank. Las Fumaroles (near top center), a thermal area below the cliffs, was the source of an explosive eruption in December 1994 that also produced an avalanche and lahar down the Río Sucio.

Photo by Eliecer Duarte, 2001 (OVSICORI-UNA).

This image is made available under the Creative Commons BY-NC-ND 4.0 license terms.

Keywords: hydrothermal alteration | crater | outcrop | stratigraphy

Irazú