Volcano sheds a tear.
Many of the world's volcanoes are too remote for geologists to install monitoring networks, particularly when no humans are at risk to justify the expense. Vulcanologists wishing to track activity at such peaks therefore rely on satellite monitoring to keep an eye on events, with occasional visits when possible. As part of this process, NASA's Earth Observing satellite caught Mawson peak on faraway Heard Island shedding a lava tear onto its glacial blanket. The eruption deposited the small black streak on the south western side.
These images were taken as follow up, after infrared satellite monitors showed signs of activity. The 2750 metre peak is named after the famous Australian geologist and Antarctic explorer Douglas Mawson. It is one of three volcanoes on Heard island in the southern Indian Ocean, about 2000 Km north of Antarctica and 2200 Km southeast of Africa. It is one of Australia's most remote territories, highest non-Antarctic mountain, and one of its only two currently active volcanoes, having erupted regularly since 1985.
Mawson Peak is a 20 Km wide resurgent stratovolcanic cone sitting on the edge of the larger Big Ben caldera (a collapse feature resulting from magma chamber roofs falling in as they empty in an eruption). Heard Island is the exposed part of the caldera, jutting out of the Kerguelen Plateau. It lies deep in the prevailing westerlies of the furious fifties that circle Antarctica, and sees cold temperatures and sea level snow throughout the year. Fourteen glaciers radiate out from its vent area. An air force base was maintained there in the 1950's, but is now long abandoned, since maintaining it was very expensive. It is so remote and harsh that only a few expeditions have explored it since its discovery in 1853, the last scientific one being in the summer of 2003-4.
The plateau is a micro-continental strip left behind when Gondwana rifted apart. Rising 3700 metres above the abyssal plains, it was overlain between 115 and 110 million years ago by the eruption of a large igneous province during the rifting of India and Australia. Intense volcanism was interspersed with longer periods of quiet. Soil layers with charcoal, fossils and fragments of gneiss indicate the plateau was above the waves for three extended periods since the eruptions started, finally subsiding under the waves about twenty million years ago. Its sedimentary rocks are similar to parts of India and Australia, implying it sat somewhere between them until they split, when it became a tectonic ribbon covered in kilometres of lavas from a hotspot under the Indian Ocean. It is the second largest oceanic plateau on Earth.
Monitoring global volcanism in this manner allows us to build up a more representative sample by including remote areas, where humans won't notice (or report on) any effects of an eruption. This helps us grow our understanding of plate tectonics and volcanism as a process affecting the entire planet.
Loz
Image credit: NASA.