Geophysical location: Erebus lies in the West Antarctic Rift System over relatively thin (20 km) crust in what is (excellently) called the Terror Rift. This is an intracontinental rift zone that drives extension, producing the Terror Rift graben, which also hosts other nearby volcanoes on Ross Island (Mt. Terror and Mt. Bird). The source of the magma at Erebus is referred to as the “Erebus Plume” that is rising from asthenosphere (in the mantle) at velocities of ~6 cm/year. This is what is driving the extension in the Terror Rift graben.
Summary: Mt. Erebus erupts silica-undersaturated lavas in the form basanite and phonolite (note: most lavas, like basalt or rhyolite, are silica-saturated). These compositions are typical in rift systems and are found at places like the East African Rift or the Rhine Graben in Germany. Erebus is one of the few volcanoes in the world (along with Erta’Ale, Nyiragongo, Kilauea, Villarrica and Masaya) with an active lava lake and this lake has been present since at least the 1960’s. The lava lake has a variable 5 to 15 meter / 15 to 45 foot radius inside the main crater on the volcano. This crater is 120 meters / 400 feet deep with a inner crater that is 100 m / ~300 feet deep where the convecting phonolite lava lake sits. One of the most remarkable features in the lava lake are the up-to-10-cm anorthoclase crystals (pdf link) in the lava. Most crystals in erupting lava are less than a centimeter in size, so these aptly-called megacrysts are quite unique (and not well understood). The lava lake was buried briefly in 1987 by a landslide (similar to what happened at Halema’uma’u Crater this year), but lava retook the bottom of the crater to form a new lake by 1990. Most of the summit features at Erebus are likely less than 37,000 years old, although ancestral volcanoes dating as far back as 1.3 million years existed in the spot that Erebus sits (Esser et al., 2004). Since 250,000 years ago, Erebus has erupted at an average rate of 1.2 to 4.0 km3/1000 years, which is relatively low for volcanoes of its type.
The phonolite lava lake in the inner crater at Mt. Erebus. Image taken in 1983, courtesy of MEVO.
Current status: Active. The volcano has frequent strombolian eruptions that have been detected remotely via video and infrasound monitoring. There is a collection of movies of Erebus erupting available on the MEVO website and are well worth the time. There has been frequent harmonic tremor noted at Erebus since 2000 and likely represents the emplacement of a dike at depth, although the main reservoir for the volcano is believe to lie only tens to hundreds of meters below the crater floor (Aster et al., 2003).
Notable Recent Eruptions and History: The volcano was erupting in 1841 when it was discovered by James Ross and has erupted frequently since then, upwards of 200 times between 1986-1990 alone. Most known eruptions at Erebus dating back several thousand years are only up to a VEI 2, so there is no evidence that Erebus has large explosive eruptions, although tephra/ash/aerosols from the volcano is found in the ice across Antarctica. This evidence of aerosol dispersal across the continent is likely from the passive degassing of the volcano rather than an explosive event. The volcano releases 7700-25900 tonnes of SO2, 6600-13300 tonnes of HCl and 4000-6000 tonnes of HF annually and this produces impurities in Antarctic snow. Erebus is likely the source of many impurities in the snow, including elevated levels of copper, zinc, cadmium, vanadium, arsenic, gold, lead and antimony (Zreda-Gostynska et al., 1997).
Mitigation: None needed as the eruptions are small and beyond research stations (and penguins), there are no permanent settlements near the volcano.
Selected resources of Erebus:
Aster, R., Mah, S., Kyle, P., McIntosh, W., Dunbar, N., Johnson, J., Ruiz, M., McNamara, S., 2003. Very long period oscillations of Mount Erebus Volcano, Journal of Geophysical Research B. 108, 2522.
Aster, R., McIntosh, W., Kyle, P., Esser, R., Bartel, B., Dunbar, N., Johns, B., Johnson, J., Kartsens, R., Kurnik, C., McGowan, M., McNamara, S., Meertens, C., Pauly, B., Richmond, M., Ruiz, M., 2004. Real-time data received from Mount Erebus Volcano, Antarctica, EOS. 85, 97, 100-101.
Esser, R., Kyle, P., McIntosh, W., 2004. 40Ar/39Ar dating of the eruptive history of Mount Erebus, Antarctica: volcano evolution, Bulletin of Volcanology. 66, 671-686.
Kyle, P., Moore, J.A., Thirlwall, M.F., 1992. Petrologic evolution of anorthoclase phonolite lavas at Mount Erebus, Ross Island, Antarctica, Journal of Petrology. 33, 849-875.
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 B. 102, 15039-15055.
Gases and steam coming from Mt. Erebus in Antarctica.