deposited the ejecta and lapilli pumice units on the summit. Tephra bands are also found in other glaciers of the region. They form when snow accumulates on top of tephra that fell onto ice and in the case of Mount Melbourne they indicate eruptions during the last few thousand years. Volcanic sediments from Mount Melbourne are also found in Terra Nova Bay. Volcanic field Mount Melbourne is surrounded by a volcanic field consisting of 60 exposed volcanoes, which have the form of scoria cones and tuff rings with hyaloclastite deposits, lava flows and pillow lavas. Some of these volcanoes formed under ice. The volcanic field forms a peninsula which is separated by steep faults from the Transantarctic Mountains to the north. Among these volcanoes is Shield Nunatak southwest from Mount Melbourne, a subglacial volcano, now exposed, that may have formed during the last 21,000 to 17,000 years. The Cape Washington ridge consists mostly of lava, including pillow lava, overlaid by scoria cones, and is the remnant of a shield volcano. Edmonson Point is another volcanic complex in the volcanic field that formed partly while interacting with glaciers and partly through phreatomagmatic activity. Other volcanoes in the field are Baker Rocks, Oscar Point and Random Hills. These volcanoes are aligned mainly in a north–south direction, with palagonitized outcrops that expose dikes. Perfectly preserved scoria cones occur at Pinckard Table north of the volcanic field, while Harrow Peak is a heavily eroded lava plug. The total volume of volcanic rocks is about and their emplacement apparently altered the path of the Campbell Glacier. Geology Mount Melbourne is part of the McMurdo Volcanic Group, which includes the active volcano Mount Erebus. This volcanic group is one of the largest alkaline volcanic provinces in the world, comparable with that of the East African Rift, and is subdivided into the Melbourne, the Hallett and the Erebus volcanic provinces. The volcanic group consists of large shield volcanoes mainly near the coast, stratovolcanoes and monogenetic volcanoes which formed parallel to the Transantarctic Mountains. Volcanic activity of the McMurdo Volcanic Group is tied to continental rifting and commenced during the Oligocene. It is unclear whether this is caused by a local hotspot beneath the area or mantle convection in the area of the West Antarctic Rift. The latter is one of the largest continental rifts on Earth but little known and possibly inactive today. The Ross Sea and