Black and white lantern (dark) slide of Mexican landscape with the volcanoes Popocatepetl and Itzaccihuatl in the distance.

Black and white lantern slide of Mexican landscape with the volcanoes Popocatepetl and Itzaccihuatl in the distance, looking southwest.

Black and white lantern slide of several people gathered around a shallow, smoking pit at the Solfatara volcano in Pozzuoli, Italy.

Black and white photograph of the Solfatara di Pozzuoli volcanic mud pots.

Black and white photograph of the Solfatara di Pozzuoli volcano fumerole "Boca Grande." A group of people is visible to the right of the Boca Grande. One person is standing in front of the Boca Grande, and a building is visible on the right side of…

Lava flows at Craters of the Moon National Monument, Idaho.

Sitting at the entrance to a cave at Craters of the Moon National Monument, Idaho.

Sitting on a lava flow at Craters of the Moon National Monument, Idaho.

Volcanic cone at Craters of the Moon National Monument, Idaho.

Lava flows at Craters of the Moon National Monument, Idaho.

Lava flows at Craters of the Moon National Monument, Idaho.

Water hole marker at Craters of the Moon National Monument, Idaho.