geolinde

Plate tectonics, volcanism, landslides, erosion and deposition—and their interactions—are all very evident in this view of the Crater Highlands along the East African Rift in Tanzania. The image shows landforms using color and shading. Color indicates height, with lowest elevations in green and highest elevations in white. Shading shows the slope. The vertical relief has been exaggerated by a factor of 2 to reveal greater detail about the landscape. The image is oriented as though you were looking from the north toward the southwest.

Lake Eyasi is in blue at the top of the image, and a smaller lake occurs in Ngorongoro Crater. Near the image center, elevations peak at 3,648 meters (11,968 feet) at Mount Loolmalasin, which is south of Ela Naibori Crater. Kitumbeine (left) and Gelai (right) are the two broad mountains rising from the rift lowlands. Mount Longido is seen in the lower left, and the Meto Hills are in the right foreground.

The East African Rift is a zone of spreading between the African (on the west) and Somali (on the east) crustal plates. Two branches of the rift intersect here in Tanzania, resulting in distinctive and prominent landforms. One branch trends nearly parallel to this southwesterly view and includes Lake Eyasi and the very wide Ngorongoro Crater. The other branch is well defined by the lowlands that trend left to right across the image (below center, in green). Volcanoes are often associated with spreading zones where magma, rising to fill the gaps, reaches the surface and builds cones. Craters form if a volcano explodes or collapses. Later spreading can fracture the volcanoes, which is especially evident on Kitumbeine and Gelai Mountains (left and right, respectively, lower center).

The Crater Highlands rise far above the adjacent savannas, capture moisture from passing air masses, and host rain forests. Over time, streams erode downward toward the level of the adjacent rift, deeply dissecting the volcanic slopes. This is especially evident on the eastern flanks of Mount Loolmalasin (left of center). Landslides also occur here. In particular, the small but steep volcanic cone nearest the image center has a landslide scar on its eastern (left) flank, and topographic evidence shows that the associated landslide deposits extend eastward 10 kilometers (6 miles) across the floor of the rift. Such a long run of landslide debris is unusual but not unique on Earth.

• View Size: 48 kilometers wide (30 miles) by 230 kilometers (140 miles) distance
• Location: 3 degrees South latitude, 36 degrees East longitude
• Orientation: View 35� south of west, 15� below horizontal
• SRTM Data Acquired: February 2000

Image courtesy NASA/JPL/NGA Shuttle Radar Topography team

The views from the top of Mount Kilimanjaro—a 5,895-meter (19,341-foot) dormant stratovolcano in Tanzania—are as surreal as they are spectacular. After ascending through multiple ecosystems—including cropland, lush rainforest, alpine desert, and a virtual dead zone near the summit—climbers can find themselves peering down on a thick blanket of clouds below that seems to stretch endlessly in the distance.

But in the immediate foreground, ice dominates the view. Looking north, a shelf-like block of ice with a sharp vertical cliff sits on an otherwise featureless, sand-covered plateau. In the other direction, a second ice field spills off the edge of the plateau, down the mountain’s southern face.

Kimberly Casey, a glaciologist based at NASA’s Goddard Space Flight Center, was savoring the views from Kilimanjaro’s summit and caldera when she snapped these panoramic images of Kilimanjaro’s northern (middle) and southern (bottom) ice fields. The Advanced Land Imager on NASA’s Earth Observing-1 satellite acquired the top image, which shows some of the same ice fields from above on October 26, 2012.

Casey was taking part in a September 2012 research expedition to Kilimanjaro to study the ice at the summit. For scale, bright tents that were part of the scientists' base camp are visible in the lower left of the northern ice field image.

Despite Mount Kilimanjaro’s location in the tropics, the dry and cold air at the top of the mountain has sustained large quantities of ice for more than 10,000 years. At points, ice has completely surrounded the crater. Studies of ice core samples show that Kilimanjaro’s ice has persisted through multiple warm spells, droughts, and periods of abrupt climate change.

But trends beginning more than a century ago suggest Kilimanjaro’s peaks may soon be ice-free. Between 1912 and 2011, the mass of ice on the summit decreased by more than 85 percent. Researchers say it’s no longer a question of whether the ice will disappear but when. Estimates vary, but several scientists predict it will be gone by 2060.

Rising air temperatures due to global warming could be contributing to the ice loss, but a number of other factors are just as important, if not more so. An increasingly dry regional atmosphere, for example, is starving the mountain of the fresh snow needed to sustain the ice fields. Drier air is also reducing cloud cover and allowing more solar energy to warm the ice surfaces.

Casey and colleagues noticed yet another ominous sign during their 2012 expedition. The northern ice field, which had been developing a hole since the 1970s, has separated. “This was the first year that the northern ice field completely divided into two,” said Casey. “We were able to walk on land—or we could have even ridden a bicycle—directly through the rift.”

See more images of Casey’s Kilimanjaro expedition on Flickr.

• References

• Cullen, N. (2012, October 1) A century of ice retreat on Kilimanjaro: the mapping reloaded.The Cryosphere Discuss.
• Earth Science Picture of the Day. (2012, October 18) Kilimanjaro Icefield in September. Accessed November 7, 2012.
• Hardy, D. (n.d.) Kilimanjaro climate and glaciers. Accessed November 7, 2012.
• NASA. (2012, April 2) Meet Kimberly Casey: Studying how debris influences glaciers. Accessed November 7, 2012.
• NOVA. (n.d.) Volcano above the clouds. Accessed November 7, 2012.
• Thompson, L. (2009, September 29) Glacier loss on Kilimanjaro continues unabated. Proceedings of the National Academy of Sciences.
• UNEP. (2012, August) Africa without ice and snow. Accessed November 7, 2012.

NASA Earth Observatory image by Jesse Allen and Robert Simmon, using ALI data from the NASA EO-1 team. Photos by Kimberly Casey. Caption by Adam Voiland.

Instrument(s): 

EO-1 - ALI