CO2 allows volcanoes to form persistent lava lakes at the surface

Antarctica's only active volcano shows how CO2 allows volcanoes to form persistent lava lakes at the surface​

A joint University of Utah and University of Canterbury New Zealand study shows how CO₂ deep underground helps magma avoid being trapped deep in the Earth and allows it to reach and pool at the surface.

"Mount Erebus is an example of a CO₂-dominated rift volcano, a complement to the more widely known arc volcanoes of the Pacific Rim and elsewhere, dominated by H₂O," adds New Zealand co-investigator Graham Hill, the study's lead author."Understanding both H₂O and CO₂ volcanoes is important for calculating the budget of such volatile gases deep in the Earth that involves injection of material into Earth's mantle and its return to the surface to start all over again", Wannamaker says.

Erebus exemplifies a family of volcanoes with an alkalic chemical composition, with lavas relatively rich in sodium, potassium and other elements including rare Earth's elements, while being relatively poor in silica.

Alkalic volcanoes are very different from volcanoes such as in the Cascade Range extending from northern California through British Columbia to Alaska. The Cascades are found in a place where Earth's tectonic plates are pushing toward each other, with the crust of the ocean forced below the crust of the continent. As that ocean crust sinks into the Earth and partially melts, the water in the rocks becomes part of the melt and is the dominant "volatile," or molecule that easily exsolves, or bubbles out of a solution like fizz out of a carbonated drink.

That evolving magma rises into and through the crust, but typically does not make it to the surface because, as the pressure from the overlying crust diminishes with ascent, the water flashes out, sometimes explosively as in the case of Mount St Helens in 1980 or Mount Lassen in 1912. The remaining magma stalls and freezes in place, typically at a depth of around three miles (five kilometers).

Alkalic volcanoes are very different from volcanoes such as in the Cascade Range extending from northern California through British Columbia to Alaska.