Since the beginning of a recent eruption, a dense plume of water vapor, gas, and ash has concealed the summit of the Nabro volcano. New images from June 29 finally provided a nearly unimpeded view of the summit, where lava flowed out of the erupting vent and down the volcano's slope.
Located in the East African nation of Eritrea, Nabro began its eruption explosively on June 12, 2011. The powerful eruption sent plumes of ash streaming over North Africa and the Middle East, pumping vast quantities of sulfur dioxide into the atmosphere. The ash halted flights in East Africa for a time. The eruption killed seven people, according to the Eritrean government, and other reports indicate that thousands were affected in both Eritrea and Ethiopia, though news from the region is sparse.
More recently, the volcano has eased into a quieter, lava-oozing phase, as shown in these images from the Advanced Land Imager (ALI) on the Earth Observing-1 (EO-1) satellite. The top image shows the volcano in visible and infrared light (shortwave infrared, near infrared, and green). The hot lava glows orange-red, fading to black as it cools. The long flow on the west side of the volcano is mottled with black, a sign that the surface is cooling. The lava to the east and south of the vent appears to be newer, because little of it has cooled. It's possible that the cooling lava in the western flow diverted the fresh lava to the south and east.
The lower image provides a natural color view of the volcano. A small, slightly brown plume rises from the vent, and ash blackens the ground to the west and south.
Throughout the eruption, satellite images have been nearly the only source of new information about activity at the volcano. Detailed images like these provide insight into how erupting lava is behaving. For example, volcanologist Erik Klemetti used previous images from ALI to estimate how quickly the lava is moving and to guess at how thick (viscous) the lava is.
The Nabro Volcano hasn't erupted in recorded human history, but lava flows near the volcano are relatively recent geologically. Nabro is part of the active East African Rift, where three tectonic plates are pulling away from each other. As the Earth's crust thins in the region, volcanoes rise in weak spots.
NASA Earth Observatory images by Robert Simmon, using EO-1 ALI data. Caption by Holli Riebeek.