Arsia Mons

Today's VIS image shows a cross section of Arsia Mons, including part of the summit caldera (top of image). A large volcanic crater known as a caldera is located at the summit of all of the Tharsis volcanoes. These calderas are produced by massive volcanic explosions and collapse. The bottom half of the image contains multiple collapse features, including both circular and elongate depressions. Collapse features occur on all three Tharsis volcanoes (Ascreaus Mons, Pavonis Mons and Arsia Mons), on the southwestern and northeastern flanks. This alignment may indicate a large fracture/vent system was responsible for the eruptions that formed all three volcanoes. The scalloped depressions and lines of craters are most likely created by collapse of the roof of lava tubes. Lava tubes originate during eruption event, when the margins of a flow harden around a still flowing lava stream. When an eruption ends these can become hollow tubes within the flow. With time, the roof of the tube may collapse into the empty space below. The tubes are linear, so the collapse of the roof creates a linear depression. In this region, the complexity of the collapse has created a unique surface. Arsia Mons is the southernmost of the Tharsis volcanoes. It is 450 km (270 miles) in diameter, almost 20 km (12 miles) high, and the summit caldera is 120 km (72 miles) wide. For comparison, the tallest volcano on Earth is Mauna Kea. From its base on the sea floor, Mauna Kea measures only 10.2 km (6.3 mi) high and 121 km (75 mi) in diameter.