Elysium Mons

This image shows Elysium Mons. This volcano is much smaller than the Tharsis volcanoes. It is only 9 km tall, and is about 240 km in diameter. Thus, it is nearly the same size as the largest Hawaiian volcanoes. Like the Tharsis Montes, however, Elysium Mons sits on a large pile of lava flows. This lets it rise 12 km above the mean planetary elevation. It grades so smoothly into the surrounding lava plains that its base is hard to see. A smaller volcano, Albor Tholus, can also be seen. It is partly buried by the lava plains surrounding Elysium Mons. Note the number of channels in this image. In places, these features look a lot like lunar sinuous rilles. They are all large flat-bottomed valleys. They begin abruptly in broad depressions. And their sources seem to form a ring centered on Elysium Mons. Like sinuous rilles on the Moon, these valleys might be lava channels. However, water is a more likely cause for their formation. Specifically, ground ice appears to have been widespread in the Elysium region. Such ice is easily melted near hot magmas. Thus, melt water provides a ready source for erosion in the Elysium region. Further, the loss of a lot of ground ice can cause collapse depressions near the channel sources. (from digital mosaic of Viking 1 images, prepared for NASA by the U.S. Geologic Survey, published on the Mars CD-ROM VO_2014.)

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