Desert Contrast

Seen from space, few other dormant volcanoes look as exotic and spectacular as Waw an Namus. The volcano, located deep in the Sahara Desert in the Fezzan region of southwestern Libya, appears as a smear of dark basaltic ash and tephra that contrasts sharply with the light-colored sand of the Sahara Desert. The Operational Land Imager (OLI) on Landsat 8 captured this view of the feature on May 29, 2015. While the precise date of the most recent eruption is not known, the lack of erosion and weathering implies that it probably occurred in the last few thousand years. South of the ash field, mud streams have begun the slow process of eroding the tephra and ash away. The ash field extends around a much smaller caldera that is about 4 kilometers (2 miles) wide. Calderas are hollowed-out circular depressions that form at the summit of volcanoes when magma is withdrawn or erupted from a shallow underground magma reservoir.