Mount Melbourne is a ice-covered stratovolcano in Victoria Land, Antarctica, between Wood Bay and Terra Nova Bay. It is an elongated mountain with a summit caldera filled with ice with numerous parasitic vents; a volcanic field surrounds the edifice. Mount Melbourne has a volume of about and consists of tephra deposits and lava flows; tephra deposits are also found encased within ice and have been used to date the last eruption of Mount Melbourne to . The volcano is fumarolically active.
The volcano is part of the McMurdo Volcanic Group, and together with The Pleiades, Mount Overlord, Mount Rittmann and the Malta Plateau forms a subprovince, the Melbourne volcanic province. The volcanism is related both to the West Antarctic Rift and to local tectonic structures such as faults and grabens. Mount Melbourne has mainly erupted trachyandesite and trachyte, which formed within a magma chamber; basaltic rocks are less common.
Geothermal heat flow on Mount Melbourne has created a unique ecosystem formed by mosses and liverworts that grow between fumaroles, ice towers, and ice hummocks. This type of vegetation is found at other volcanoes of Antarctica and develops when volcanic heat generates meltwater from snow and ice, thus allowing plants to grow in the cold Antarctic environment. These mosses are particularly common in a protected area known as Cryptogam Ridge within and south of the summit caldera.
Description
Mount Melbourne lies in North Victoria Land, facing Wood Bay of the Ross Sea. To the southeast lies Cape Washington and due south lies Terra Nova Bay; Campbell Glacier runs west from the volcano and Tinker Glacier lies north of the volcanic field. The seasonal Italian Mario Zucchelli Station lies from the volcano; the 5th Chinese station in Antarctica (due to be completed in 2022), the Korean Jang Bogo Station, the German Gondwana Station and a neutrino detector are also in the area. Mount Melbourne was discovered and first recognized as a volcano by James Ross in 1841 and named after William Lamb, 2nd Viscount Melbourne, who was then the prime minister of the United Kingdom. The volcano and its surroundings were investigated by New Zealand-based parties in the 1960s, by German ones in the 1970s and 1980s and by Italian-based parties in the 1980s and 1990s. The volcano and its summit can be accessed from the stations by helicopter.
Volcano
Mount Melbourne is an elongated stratovolcano formed by lava flows and tephra fall deposits, with gentle slopes. The volcano is uneroded and forms a cone with a base area of . Viewed from afar, Mount Melbourne has a nearly perfect cone-like profile that has drawn comparisons to Mount Etna in Italy and Mount Ruapehu in New Zealand. Lava domes and short lava flows form the summit while volcanic mounds, cones, domes and scoria cones dot its flanks; from the summit is a large parasitic vent on the north-northeastern slope, which generated several lava flows. Part of the edifice rises from below sea level. Pyroclastic flow depositsa rarity for Antarctic volcanoeshave been reported. The total volume of the edifice is about .
A crater or caldera sits at the top of the volcano. The highest point of the volcano lies east-northeast of the caldera and reaches elevation. The caldera has an incomplete rim and is filled with snow, leaving a depression. The rim of the caldera is covered by volcanic ejecta including lapilli and lava bombs, probably the products of the most recent eruption, which overlie a layer of pumice lapilli. Three small, nested craters formed by phreatomagmatic eruptions occur on the southern rim of the summit caldera. Pyroclastic fall deposits crop out in the northern rim of the caldera and there are more alternating lava-tephra sequences elsewhere in the summit region. There is evidence of past structural instability (collapse structures) on the eastern and southeastern flanks, and an arcuate (with the shape of an arc) scarp on the eastern flank appears to be an incipient sector collapse.
Except for geothermal areas, the ground is bouldery. Some of the coastal areas around the volcano are ice-free and rocky. Frost heave has been observed in the summit region. Small creeks flow down the eastern flank of Mount Melbourne; they are fed by meltwater during summer and quickly disappear when the snow is gone.