Antarctica’s Mount Erebus may be covered with glaciers, but they do little to cool the volcano’s molten core. A lava lake is visible at the volcano’s summit.
After more than a decade of inactivity, Mount St. Helens rumbled back to life in September 2004. An ongoing series of tremors within the volcano coupled with upward movement of magma toward its caldera prompted geologists to issue a Level 3 alert on October 2, stating that Mount St. Helens could experience a moderately severe eruption at any time. In order to help geologists and volcanologists assess the nature and magnitude of the risk, on September 24, 2004, NASA flew a low-altitude aircraft carrying the MODIS/ASTER Airborne Simulator (MASTER) directly over the volcano to obtain high-resolution images of its caldera.
In early September 2007, Tanzania&#rsquo;s Ol Doinyo Lengai Volcano erupted, sending a cloud of ash into the atmosphere. The volcanic plume appears pale blue-gray, distinct near the summit, and growing more diffuse to the south. The charcoal-colored stains on the volcano’s flanks appear to be lava, but they are actually burn scars left behind by fires that were spawned by fast-flowing, narrow rivers of lava ejected by the volcano.