Emi Koussi Volcano, Chad, North Africa
Posted December 8, 2002
high resolution 1000 pixel-wide image
Emi Koussi is a high volcano that lies at the south end of the Tibesti
Mountains in the central Sahara in northern Chad. The volcano is one of
several in the Tibesti massif, and reaches 3415 m in altitude, rising
2.3 km above the surrounding sandstone plains. The volcano is 65 km
wide.
This view of the Emi Koussi caldera was taken with an 800 mm lens on
November 21, 2002. It is detailed to the point that it doesn’t include
the entire 10-km diameter of the caldera, but reveals individual lava
strata within the walls of the summit cliffs. Nested within the main
caldera is a smaller crater that contains white salts of a dry lake at
its lowest point. Here too, strata are visible in the walls of the
smaller crater. The smaller crater is surrounded by a region of darker
rocks—a geologically young dome of lava studded with several small
circular volcanic vents.
Emi Koussi has been used as a close analog to the famous Martian volcano
Elysium Mons.
One of the most important morphological differences between volcanoes
on Mars and Earth is the widespread furrowing of the surface due to
flowing water on terrestrial volcanoes. The furrows are shallow
valleys. Larger channels have a different origin. Major channels can be
seen on volcanoes on both planets and indicate low points in caldera
rims where lava spilled out of pre-collapse craters.
Astronaut photograph ISS005-E-20451
was provided by the Earth Sciences and Image Analysis
Laboratory at Johnson Space Center. Additional images taken by
astronauts and cosmonauts can be viewed at the NASA-JSC Gateway to
Astronaut Photography of Earth.