Deposits of the Liberia Tuff are exposed in steep-walled gullies SW of the volcano. The rhyolitic ignimbrite was erupted about 1.6 million years ago and blanketed an area of 3500-4000 sq km. The Liberia Tuff differs from other ignimbrite deposits in NW Costa Rica in containing a large amount of biotite phenocrysts. Eruption of the 25 cu km ignimbrite was associated with formation of the 15-km-wide Guachipelín caldera, inside which the modern Rincón de la Vieja massif was constructed.

Photo by Lee Siebert, 1998 (Smithsonian Institution).

Rincón de la Vieja