Ascraeus Mons

This VIS image shows part of the complex caldera at the summit of Ascraeus Mons. Ascraeus Mons is the northernmost and tallest of the three large aligned Tharsis volcanoes. Calderas are found at the tops of volcanoes and are the source region for magma that rises from an underground lava source to erupt at the surface. Volcanoes are formed by repeated flows from the central caldera. The final eruptions can pool within the summit caldera, leaving a flat surface as they cool. Calderas are also a location of collapse, creating rings of tectonic faults that form the caldera rim. Ascraeus Mons has several caldera features at its summit. Ascraeus Mons is 18 km (11 miles) tall, for comparison Mauna Kea - the tallest volcano on Earth - is 10 km tall (6.2 miles, measured from the base below sea level).