The broad Emi Koussi volcano is a shield volcano located
in northern Chad, at the southeastern end of the Tibesti Range. The
dark volcanic rocks of the volcano provide a sharp contrast to the
underlying tan and light brown sandstone exposed to the west, south, and
east (image lower left, lower right, and upper right).
Emi Koussi was formed from relatively low viscosity lavas—flowing more like motor oil than toothpaste—and explosively-erupted ignimbrites that produce a characteristic low and broad structure covering a wide area (approximately 60 by 80 kilometers).
This astronaut photograph highlights the entire volcanic structure.
At 3,415 meters above sea level, Emi Koussi is the highest summit of
Africa's Sahara region. The summit includes three calderas formed
by powerful eruptions. Two older and overlapping calderas form a
depression approximately 12 kilometers by 15 kilometers in area bounded
by a distinct rim (image center). The youngest and smallest caldera, Era Kohor, formed as a result of eruptive activity within the past 2 million years.
Young volcanic features, including lava flows and scoria cones are
also thought to be less than 2 million years old. There are no
historical records of eruptions at Emi Koussi, but there is an active
thermal area on the southern flank of the volcano.
Astronaut photograph ISS026-E-17074
was acquired on January 11, 2011, with a Nikon D2Xs digital camera
using a 70 mm lens, and is provided by the ISS Crew Earth Observations
experiment and Image Science & Analysis Laboratory, Johnson Space
Center. The image was taken by the Expedition 26 crew. The image has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab
to help astronauts take pictures of Earth that will be of the greatest
value to scientists and the public, and to make those images freely
available on the Internet. Additional images taken by astronauts and
cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by William L. Stefanov, NASA-JSC.