Cones with Summit Depressions

A cluster of cones with summit depressions in Coprates Chasma, Mars. These structures, morphologically speaking, resemble cinder cones. More likely, they are mud volcanoes. Mud volcanoes occur when a slurry of liquid, gas, and sediment is forced to the surface from a depth of several meters to several kilometers. They can form a wide variety of structures, including cones. (HiRISE image ESP_033986_1670)

Cinder cones (otherwise known as scoria cones) are the most common type of volcano on Earth. They’re also one of the smallest. They can often be found growing on larger volcanoes, in which case they’re dubbed as ‘parasitic.’ Cinder cones form when gaseous, fragmented volcano ejecta—called tephra or ‘cinder’—accumulates around the vent and welds together. They usually have a bowl-shaped crater at their summit.

While cinder cones abound on Earth, they have been harder to find on Mars. At least, they’re not as easily identified as the massive shield volcanoes such as Olympus Mons. Several structures might resemble cinder cones but with further investigation prove to be something different. Identifying a cinder cone on Mars is not just a matter of morphology. One should ask, for example, whether the structure is in an area of volcanic activity or has evidence of lava flows.