While active volcanoes are obvious targets of interest because they pose natural hazards, there are some dormant volcanoes that also warrant concern because of their geologic history. One such volcano is Sollipulli, located in central Chile near the border with Argentina. The volcano sits in the southern Andes Mountains within Chile’s Parque Nacional Villarica. This photograph by an astronaut on the International Space Station features the summit (2,282 meters, or 7,487 feet, above sea level) and the bare slopes above the tree line. Lower elevations are covered with green forests indicative of Southern Hemisphere summer.
The summit of Sollipulli is occupied by a four-kilometer wide caldera, currently filled with a snow-covered glacier. While most calderas form after violent, explosive eruptions, the types of rock and other deposits associated with such events have not been found at Sollipulli. Geologic evidence does indicate explosive activity occurred about 2,900 years ago, and lava flows were produced approximately 700 years ago. Together with the craters and scoria cones along the outer flanks of the caldera, this history suggests Sollipulli could erupt violently again, presenting a potential hazard to towns such as Melipeuco and the wider region.
Astronaut photograph ISS038-E-12569 was acquired on December 6, 2013, with a Nikon D3S digital camera using a 400 millimeter 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 38 crew. It has been cropped and enhanced to improve contrast, and 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, Jacobs at NASA-JSC.
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 kilometers above the surrounding sandstone plains. The volcano is 65 kilometers wide. This view of the Emi Koussi caldera is detailed to the point that it doesn’t include the entire 10-kilometer 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.