Daedalia Planum

Today's VIS image shows a small portion of the immense lava flows that originated from Arsia Mons. Arsia Mons is the southernmost of the three large aligned volcanoes in the Tharsis region. Arsia Mons' last eruption was 10s of million years ago. The different surface textures are created by differences in the lava viscosity and cooling rates. The lobate margins of each flow can be traced back to the start of each flow -- or to the point where they are covered by younger flows. Flows in Daedalia Planum can be as long as 180 km (111 miles). For comparison the longest Hawaiian lava flow is only 51 km (~31 miles) long. The total area of Daedalia Planum is 2.9 million square km – more than four times the size of Texas. A set of graben are also visible in this image. Graben are formed by extension of the crust and faulting. When large amounts of pressure or tension are applied to rocks on timescales that are fast enough that the rock cannot respond by deforming, the rock breaks along faults. In the case of a graben, two parallel faults are formed by extension of the crust and the rock in between the faults drops downward into the space created by the extension.