Mount Erebus

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Mount Erebus in Antarctica is the southernmost active volcano on Earth. 3794 metres (12,448 ft) high, it is located on Ross Island, which is also home to three inactive volcanoes, notably Mt. Terror.

The volcano has been continuously active since 1972 and is the site of the Mt. Erebus Volcano Observatory run by the New Mexico Institute of Mining and Technology. The crater is home to one of three permanent lava lakes in the world.

Mount Erebus was discovered in 1841 by polar explorer Sir James Clark Ross (whose ships were named Erebus and Terror; these ships were also used by Sir John Franklin on his disastrous search for the Northwest Passage), and first climbed (to the rim) by members of Sir Ernest Shackleton's party in 1908. The ships and the volcano were all named for Erebus, a primordial Greek god, the son of Chaos.

Air disaster

The Mount Erebus disaster occurred on November 28 1979 when an Air New Zealand DC-10 with 257 people on board for a sightseeing trip over Antarctica crashed into the lower northern slope of Mount Erebus. The aircraft was completely destroyed; a recovery team spent over a week camped at the crash site performing body recovery and accident investigation work. The remains of 213 passengers were recovered and identified; the bodies or body parts of the remaining 44 were never properly identified.

The official accident report attributed the disaster to the decision of the captain in descending to a height below the approved level, in cloud, and continuing at that height when the crew was not sure of the plane's position. However, a Royal Commission of Inquiry disagreed with the accident investigators and attributed blame to the airline company for not advising a change in the flight computer settings and in not properly training the crew in Antarctic flying conditions. The Commission of Inquiry concluded that the pilot had continued flying towards the mountain under visual flight rules because he was in clear air but was unaware that the mountain was directly in front of him because polar lighting caused a whiteout situation that made the mountain invisible. The optical illusion that the whiteout caused gave the impression that the plane was flying over a wide flat landscape, as would be expected had the plane been flying on the original flight path; consequently, the crew did not detect that the new flight path programmed into their flight navigation computer was flying them directly at Mount Erebus.

A memorial cross was later erected on an outcrop of rock that overlooks the accident site.

Topographic map of Ross Island (1:250,000 scale) from USGS Ross Island

Geology

Mt. Erebus is currently the most active volcano in Antarctica. The summit of Mt. Erebus contains a persistent convecting lava lake which undergoes several strombolian style eruptions daily. Within the past year, small ash eruptions and even a small lava flow have also been observed coming from vents near the lava lake.

Mt. Erebus (3794 meters above sea level) is classified as a polygenetic stratovolcano. The composition of the current eruptive activity on Mt. Erebus is anorthoclase-porphyric tephritic phonolite and phonolite, which constitute the bulk of exposed lava flow on the volcano. The oldest eruptive products from Mt. Erebus consist of relatively undifferentiated and non-viscous basanitic lavas that form the low, broad platform shield of the Erebus edifice. Slightly younger basanite and phonotephrite lavas crop out on Fang Ridge, an eroded remnant of an early Erebus volcano and at other isolated locations on the flanks of the Mt. Erebus edifice.

Lava flows of more viscous phonotephrite, tephriphonolite and trachyte were erupted after the basanite. The upper slopes of Mt. Erebus are dominated by steeply dipping (~30°) tephritic phonolite lava flows with large scale flow levees. A conspicuous break in slope at approximately 3200 meters is a summit plateau representing a caldera less than 100,000 years old. The summit caldera itself is filled with small volume tephritic phonolite and phonolite lava flows. In the center of the of the summit caldera is a small, steep-sided cone composed primarily of decomposed lava bombs and a large deposit of anorthoclase crystals. It is within this summit cone that the active lava lake continuously degasses. The volcano frequently produces Strombolian eruptions from several vents within its innermost crater, with the most frequent events arising from large (up to 10-m diameter) gas bubbles emerging explosively from the lava lake.

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