Wednesday, April 7, 2010

Collapsing Volcano

This image covers the northern edge of the largest volcano in the solar system, Olympus Mons. The margin of Olympus Mons is defined by a massive, tall cliff. At this location, it is nearly 7 kilometers (23,000 ft) tall. The cliff exposes the guts of the volcano, revealing interbedded hard and soft layers. The hard layers are lava and the soft layers may be dust (from large dust storms) or volcanic ash.

This HiRISE image also shows a large tongue of material that has flowed over the giant cliff. While superficially similar to lava flows, this flow is actually a landslide. Most scientists think the the cliffs also formed by landslides, just much bigger ones. All this collapse is driven by the weight of the huge volcano exceeding the strength of the rocks of which it is composed.

Photo credit: NASA/JPL/University of Arizona

(Note: I wanted to explain my choice of link with respect to "weight of the huge volcano" in the second paragraph. As you can see, I chose to link to Kim Stanley Robinson's anthology, The Martians; the reason being, in his 1985 novella, Green Mars (not to be confused with the novel of the same name), Robinson devoted several pages (pp. 192-95) to this topic, explaining why the weight of Olympus Mons created such a towering escarpment that encircles the base of the volcano. This section of the novella is too long to include as part of this post, so I'll leave it to my readers to dig up the anthology to read for themselves.)

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