Cone on Pavonis Mons

Cone on Pavonis Mons, a photo by Lunar and Planetary Institute on Flickr.

Via Flickr:
This HiRISE image shows a small cone (volcano composed of cinders) that occurs on the much larger Pavonis Mons shield volcano in the Tharsis province on Mars. Giant volcanoes, both on Earth and Mars, often contain smaller volcanic vents where local smaller eruptions of magma occur over the long history of their development. Cinder cones result from eruptions of relatively gas-rich magma, in which the gas bubbles cause fragmentation of the magma into small pieces, which upon eruption build cinder cones like this one.