Mount Erebus volcano is an intraplate volcano and belongs to the McMurdo volcanic group, located in the so-called Rift of Terror, which is part of the West Antarctic Rift system. This area is an area where the extension takes place and has thinned the crust to 20 km and allows magma to rise. The source of magma below Erebus is sometimes described as an upper mantle plume at speeds of around 6 cm per year.
The Erebus volcano has suffered at least one or two caldera formations. It contains a summit plateau at approximately 3,200-m, marking the edge of the younger caldera, which formed during the late Pleistocene and on which the modern cone was built.
It consists of the summit of the elliptical 500 x 600 m wide, 110 m deep crater, containing the famous active lava lake, within an internal crater 250 m wide, 100 m deep.
Erebus Lava Lake
Mount Erebus is notable for its active phonolite anorthoclase-feldspar lava lake, which has been in continuous activity since 1972 at least, but probably much longer. Lava lake from the MT Erebus volcano is connected to a long-lived, open and stable magma plumbing system, which could have been in place for the last 17,000 years.
Current activity in the lava lake includes spattering and sometimes strombolian explosions, which can eject bombs out of the crater.
Persistent lava lakes are very rare and require a delicate balance between heat source and heat loss. Heat source is provided by rising magmatic gases from the magma chamber through a liquid fill conduit and is countered by the intense heat lost on the surface of the lava lake. There are only a handful of long-lived lava lakes in the world: Erta Ale volcano (Ethiopia), Nyiragongo (DRC), Ambrym (Vanuatu), often on the Kilauea volcano in Hawaii, and only occasionally on other volcanoes.
Although Erebus is perhaps among the most inhospitable and remote of any active volcano in the world, it is relatively well controlled. The Mount Erebus Volcano Observatory (MEVO), led by the New Mexico Institute of Mining and Technology and the National Science Foundation, operates regular field surveys and measurements from the McMurdo station. There is even a webcam on the edge of the crater! Satellites monitor CO2, SO2 and other gases emitted by Erebus, which influence the Antarctic atmosphere, which is of particular importance for the global climate.
Sources, bibliography and references
- Mount Erebus Volcano Observatory
- Mt Erebus webcam
- Smithsonian / GVP volcano info
-Kyle de esser, R., P., McIntosh, w. (2004) "40Ar / 39Ar dating from the eruptive history of Mount Erebus, Antarctica: evolution of the volcano", Volcanology Bulletin, v 66, pp 671-686.
-Zreda-Gostynska, G., Kyle, P., Finnegan, D., Prestbo, K.M. (1997) "Volcanic gas emissions from Mount Erebus and their impact on the Antarctic environment", Journal of Geophysical Research, v. 102, pp 15039 15055
The increase in activity during the first half of 2006 and a decrease after June again. During this period, large and very large eruptions from the lava lake, vent ash or Werner vent into the inner crater were frequent.
Several "small and medium" (strombolian) eruptions were recorded during October 12-18, with one "large" eruption on October 14.
On November 23, 2001, MEVO reported that Mount Erebus produced frequent strombolian eruptions (~ 10-1 per day) and the lava lake was 15 m in diameter. Small ash explosions also took place from a vent next to the lava lake.
Activity was relatively uniform between 1980-1995, with the exception of two significant events: In 1984 there was a 3-4 month period of strombolian eruptions larger and more frequent than bombs ejected> 2 km from the summit crater.
On October 19, 1993, two moderate phreatic eruptions opened a new crater ~ 80 m in diameter in the main crater floor and expelled debris above the rim of the main northern crater.
Significant collapse of the inner crater was occurring in late 1995, although the lava lake remained virtually constant in size at ~ 20 m in diameter and generally in the same location.
1984-85 increased activity
An increase in activity began on September 13, 1984 and peaked during the month and early October, and remained at significantly higher levels than from 1972 to January 1985.
Previously, small strombolian eruptions, which occurred 2-6 times / day, had occasionally ejected bombs from the floor of the 220 m deep inner crater at the rim of the main crater.
During the greatest activity, the bombs averaged 2 m long and reached more than 10 m in length landed in all directions around the crater rim, and reached up to 1.2 km horizontal distance from the inner crater. The eruptions witnessed the distance of 60 km and the explosions were heard from 2 km.
1979 plane crash
On November 28, 1979, an Air New Zealand Tourism flight crashed at Mt Erebus, killing all 237 passengers and 20 crew on board. The accident is known as the Mount Erebus disaster.
In 1976, the lava lake was observed to have slowly increased since its discovery 4 years ago in 1972 and was approximately 100 m wide.
Throughout the 1970s, activity remained relatively constant, with a slight trend of gradual increase in the level. Strombolian eruptions occur occasionally, 2-10 per day typically, sometimes dropping bombs up to a few hundred feet above the outer rim. At times those bombs were landing outside the crater.
In 1978, the lake was 130 m wide and oval in shape, with 2 zones of active lava upwelling. Doming and the surface of the lava lake are occasionally observed, including a large bubble, which grew to ~ 80 m in height before bursting.
In 1978, lava lake activity consisted of 1) nearly circular lava outcrop zones, 2) small outgassing bubble-like eruptions, and 3) subsidence of consolidated crust along flat valleys or "zones of subduction.
Scientists attempted to descend into the inner crater in order to collect fresh samples. On December 23, 1978, New Zealand volcanologist WF Giggenbach had almost reached the bottom of the inner crater when an explosion occurred. He was hit by a small bomb above the knee, but survived unharmed, only his woolen pants were burned.