Collapsed Lava Tubes

Credits: ESA/DLR/FU Berlin (G. Neukum)

Pavonis Mons, rising roughly 12 km above the surrounding plains, is the central volcano of the three 'shield' volcanoes that comprise Tharsis Montes. Gently sloping shield volcanoes are shaped like a flattened dome and are built almost exclusively of lava flows. The dramatic features visible in the color image are located on the south western flank of the volcano.

Researchers believe these are lava tubes, channels originally formed by hot, flowing lava that forms a crust as the surface cools. Lava continues to flow beneath this hardened surface, but when the lava production ends and the tunnels empty, the surface collapses, forming elongated depressions. Similar tubes are well known on Earth and the Moon. Pit chains, strings of circular depressions thought to form as the result of collapse of the surface, are also visible.

A Perspective View of Lava Tubes

Credits: ESA/DLR/FU Berlin (G. Neukum)

This perspective view, taken by the High Resolution Stereo Camera (HRSC) on board European Space Agency's Mars Express, shows Pavonis Mons, the central volcano of the three 'shield' volcanoes that comprise Tharsis Montes.

Related Information:

• The images were acquired in the region of Pavonis Mons, at approximately 0.6° South and 246.4° East.

• Pavonis Mons, rising roughly 12 km above the surrounding plains, is the central volcano of the three 'shield' volcanoes that comprise Tharsis Montes. Gently sloping shield volcanoes are shaped like a flattened dome and are built almost exclusively of lava flows.

• The dramatic features visible in the color image are located on the south-west flank of Pavonis Mons. Researchers believe these are lava tubes, channels originally formed by hot, flowing lava that forms a crust as the surface cools. Lava continues to flow beneath this hardened surface, but when the lava production ends and the tunnels empty, the surface collapses, forming elongated depressions. Similar tubes are well known on Earth and the Moon.

• The long, continuous lava tube in the northwest of the image extends over 35 miles and ranges from approximately 1.2 miles to less than 0.17 miles (920 feet).

• Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow. Tubes form by the crusting over of lava channels and pahoehoe flows. A broad lava-flow field often consists of a main lava tube and a series of smaller tubes that supply lava to the front of one or more separate flows. When the supply of lava stops at the end of an eruption or lava is diverted elsewhere, lava in the tube system drains downslope and leaves partially empty conduits beneath the ground. Such drained tubes commonly exhibit "high-lava" marks on their walls, generally flat floors, and many lava stalactites that hang from the roof. Lava can also erode downward, deepening the tube and leaving empty space above the flowing lava.

Lava Tube in Hawaii

Courtesy of USGS: Photograph provided by Hawai`i Volcanoes National Park