The lava flow from Kilauea Volcano crossed Apa'a Street near Cemetery Road, near the town of Pahoa on the Big Island of Hawaii, on Friday. The flow began June 27; residents in the flow path have now been told to prepare for a possible evacuation. U.S. Geological Survey/AP hide caption

toggle caption U.S. Geological Survey/AP

Sicily's Mount Etna early this week, as seen from space. The bright red is lava. Snow is blue-green. Clouds are white. "Shortwave infrared, near infrared, and green light" combine to produce the colors. NASA hide caption

toggle caption NASA