The people in the left foreground are standing on the Toxtlacuaya lava flow, which traveled in a narrow lobe down into the valley filled by the flat-lying Río Naolinco lava flow. Both flows were produced about 900 years ago during a geochemically bimodal eruption which initially produced the alkaline Toxtlacuaya lava flow and then the voluminous calc-alkaline Río Naolinco flow. Although the flows erupted through the lower flanks of Cofre de Perote volcano, they are geochemically distinct from Cofre de Perote lavas.

Photo by Lee Siebert, 1999 (Smithsonian Institution).

This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.

Cofre de Perote