The little-known small volcanoes of Mars

Abstract

Huge volcanoes with diameters of >>100 km are well known from Mars. However, the planet‘s two largest volcanic provinces, Tharsis and Elysium, are also strewn with hundreds of small shield volcanoes, with diameters of several kilometers to tens of kilometers and heights of only a few hundred meters. These low shields are hard to detect in low-resolution images, and they only became accessible for analysis after the acquisition of high-resolution images and topographic data in the last few years. They are characterized by radial patterns of lava flows and extremely shallow flank slopes of typically <0.5°, indicating low-viscosity lavas. Many other volcanic features are associated with the low shields, such as craters, fissure vents, cinder and spatter cones, lava flows, which are commonly associated with lava channels and tubes, lava inflation features, and volcanic rift zones, all of which have terrestrial analogs in basaltic volcanic provinces. The distribution of low shields does not show any obvious association with large-scale tectonic features. The low shields might represent a recent type of volcanism, which is not related to mantle plumes, but to a zone of partial melting in an anomalously warm mantle underneath a thickened crust.