Caldera of Olympus Mons, Mars
Steven Dutch, Natural and Applied Sciences, University
of Wisconsin - Green Bay
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Although these look like craters, there are actually only a few small genuine
impact craters in this picture, the largest of them on the left. The great oval
basins are actually the summit caldera of the great Martian shield
volcano Olympus Mons. Calderas form by subsidence of the summit of a volcano.
The subsidence can be catastrophic, like it was for Crater Lake in Oregon, or
gentle, as it is for the summit calderas on Mauna Loa and Kilauea in
Hawaii, and likely was here as well. These calderas are far larger than those in
Hawaii. On the far right, there are a few small oval pits and chains of small
pits. These probably formed by the collapse of lava tunnels. Lava tunnels form
when the top of a lava flow hardens and the interior keeps flowing. Later the
roof can collapse to form pits or long trenches. Such collapsed lave tubes are
also found on the earth and the Moon. The streaky textures in places are due to
thin blankets of wind-blown sediment.
Original Scene
(ESA image)
Possible Coloring
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Created 17 December 2007, Last Update
13 February 2008
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