Mount Erebus - Antarctic Volcano

The volcanic activity at Mount Erebus has been of interest ever since Shackleton's men scaled the peak in 1908.

The Mount Erebus Volcano Observatory (MEVO) a year-round interdisciplinary network of instrumentation that includes seismic, GPS, infrasonic, and weather
measurements monitors eruptive events of the volcano and the movement of lava in and beneath the summit crater. MEVO sends its data to McMurdo station and from there uses the McMurdo Internet to forward it to scientists at the New Mexico Institute of Technology, to the UNAVCO geodetic consortium, and to the larger geophysical community. (MEVO Website)

Shackleton Meets the Volcano

The craters of Mount Erebus were first visited in March 1908 by members of Shackleton's expedition, who initially noted the "vast abyss" filled with great masses of steam that rose in a column 150 to 300 meters high. During a brief clearing, they observed the crater and noted the steam explosions issuing from three well-defined openings at the bottom of the high cauldron. As recorded in the book by Shackleton (1909) the party also observed around the summit area "lumps of lava, large feldspar crystals, from one to three inches in length, and fragments of pumice; both feldspar' and pumice were in many cases coated with sulfur."

Field studies on the volcano include analysis of lava bombs and other forms of volcanic ejecta resulting from degassing explosions in the lava lake. Other studies of Mount Erebus have included core drilling into the rocky flanks of the volcano to determine the types and sequence of materials erupted and monitoring of seismic wave activity. Of particular interest has been the discovery of several layers of ice interbedded with lava flows, which indicates that in the distant past lava eruptions occurred over glaciers without completely melting the ice.

The inner crater is situated in the northeastern part of the outer crater, and the lava lake and most eruptive activity are confined to its northern half.

Did you know?

 Mount Erebus supports a broad glacier system, with, most ice sheets extending to the edges of the island.

 Termini either form abrupt cliffs which discharge ice to the marine waters of the Ross Sea on the north and west, or they merge gently with the Ross Ice Shelf along the eastern coastline.

 Of particular interest is the Erebus Glacier Tongue, an elongate, serrate-edged lobe of ice that extends for several kilometers into Erebus Bay of McMurdo Sound, where most of it floats in water as much as 400 meters deep. The glacier is 50 to 300 meters thick and lengthens about 160 meters a year.

Lava issues from the northeastern edge of the crater and flows slowly along a curved path before disappearing into a tunnel-like opening at the south edge of the lake. Degassing explosions in the lake eject lava bombs over the southern half of the inner crater and occasionally onto the floor of the outer crater. Strong eruptions from the crater have thrown bombs as high as 1000 meters and 700 meters laterally, onto the snow surface outside both craters.

The crater topography is much more rugged than expected from observations below, with some ridges more than 30 meters high, and with strange formations of ice rising above fumerole areas--the products of steam condensing and freezing immediately into some extraordinary structures which rise here and there above the surface of the snowfield.

The lava lake may be a periodic, occurrence, depending on the degree of volcanic and thermal activity in the crater. According to geologist Robert Forbes, when he observed the crater during Operation Deep Freeze in 1955, it contained only solid rock fragments. In 1974, a party of New Zealand Scientists spent several days at the summit, on one occasion rappelling into the inner crater for the purpose of collecting a sample of the molten lava. During the roped descent, gases within the lava caused ejections of small bobs of liquid rock, which splattered around the climbers and their camp; they beat a hasty retreat from the summit area.

Fire and Ice

 Ross Island is entirely volcanic in origin and is formed by four principal volcanoes-Mounts Erebus, Terror, Bird, and Terra Nova-as well as numerous smaller volcanoes and lava flows.

 Of the volcanoes, only Erebus remains active. At 3794 meters, Mount Erebus is the highest point on Ross Island and the largest, most active volcano on the Antarctic continent.

 It is almost always observed with a cloud of vapor rising from its summit crater.

 Much eruptive and seismic activity has been observed, including ejections of volcanic bombs as much as 8 meters across.

 At the summit, a l00-meter-deep outer crater about 650 meters across contains a similarly deep inner crater about 250 meters across, in which lies a lake of red, molten lava.