Mount Erebus in Antarctica is the southernmost active volcano in the world, and a rather unusual one: its summit crater contains a permanent lava lake the size of a soccer field. Few other volcanoes on Earth have a lava lake. A research team has now discovered that Erebus’ lava lake is fed by a magma tube about 20 kilometers wide and extending to a depth of 100 kilometers. The study, published in the journal Nature Communications, also produced the first 3D schematics of the magma chamber.
Another special feature of Mount Erebus is that it has been active for millions of years and its magma carries more carbon dioxide than many other volcanoes. “Erebus is an interesting volcano independent of it being in Antarctica,” Phil Wannamaker (✝ August 2022), a geologist at the University of Utah and co-author of the study, told The Antarctic Sun. “It’s one of the purest carbon dioxide-dominated volcanoes in the world.”
Mount Erebus cannot be mapped via seismic waves like other volcanoes. So Wannamaker and his team used naturally occurring electromagnetic waves to map the rocks of the Earth’s crust and mantle based on their electrical conductivity.
Their results show a nearly vertical magma tube about 20 kilometers in diameter extending into the Earth’s mantle to a depth of about 100 kilometers. About 15 kilometers below the volcano, the tube narrows into a kind of valve and turns slightly to the East.
“The two things we really saw were a fault valve that is controlling the episodic breakthrough of magma toward the surface, and second, we’re able to follow the magma continuously and completely right to the lava lake,” Wannamaker said.
Melted rock flows directly from the Earth’s mantle into the open lava lake via this so-called fault valve. Like a nozzle, it controls the flow of magma and gas upward into the lava lake. Thus, small amounts of magma and carbon dioxide are brought to the surface in pulses, rather than in a continuous flow.
The magma contains a lot of carbon dioxide, which absorbs water from the melted rock, keeping it hot and dry. This keeps the magma thin and prevents it from getting stuck as it rises through the Earth’s crust. The lava lake is thus regularly fed with melted rock, which may explain why Mount Erebus has frequent mild eruptions and its lava lake has persisted for decades, unlike water-rich volcanoes that erupt infrequently but explosively.
Wannamaker says the study of Lake Erebus-Lava is also helping geologists understand how rare chemical elements can move from the Earth’s mantle to the surface. “Rift systems such as Mount Erebus have, in some geological intervals, emitted climate-forcing levels of carbon dioxide,” Wannamaker said. “Understanding the controls and geometry of magma movements might also improve regional exploration models for rare elements that we need for everyday life.”
Julia Hager, PolarJournal
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