Photos - Kristi Wallace


Volcanic ash, or tephra, as seen under a scanning electron microscope.
Photo credit: Photo courtesy of Andrei M Sarna-Wojcicki, U.S. Geological Survey


Ukinrek Maars, two low-lying volcanoes on the Alskan Peninsula, spew ash thousands of feet into the air in this 1977 eruption.
Photo courtesy of Juergen Kienle


Kristi Wallace digs for volcanic ash in Alaska.
Photo courtesy of USGS