The approximately 4-kilometer-wide Dendi Caldera includes some of this silica-rich volcanic rock: the rim of the caldera, visible in this astronaut photograph, is mostly made of poorly consolidated ash erupted during the Tertiary Period (approximately 65–2 million years ago).
Formed during four explosive eruptions that took place between 300,000 and 90,000 years ago, the volcanic caldera is now home to human settlements and 17 younger volcanoes.
This natural-color image from the Landsat satellite on October 5, 2000, shows El Aguajito Caldera, Las Tres Vírgenes, and La Reforma Caldera on the Baja Peninsula.