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Scientists Find 91 Volcanoes Underneath Antarctica's Melting Ice

Geologists analyzing ice-penetrating radar data on Antarctica have found an additional, previously unknown 91 volcanoes, many of them in active rift zones across the continent.
By Joel Hruska
Erebus-Feature

Geologically, Antarctica isn't easy to study. Nearly all of it (98 percent) is covered by ice, with an average depth of 1.1 miles.. This has certain obvious impacts on our ability to measure anything that isn't tall enough to break through that ice, and we don't have a thorough understanding of the ground underneath the ice sheet as a result. Researchers, pouring data from ice-penetrating radar, have identified 91 new volcanoes that dot the face of the continent, which means Antarctica now has the densest population of discovered volcanoes on Earth; significantly higher than Africa, the previous record-holder.

There are limits to what we can study from almost a mile "above" the features in question. The study only looked for evidence of cone volcanoes, even though there's good reason to think there are other types of volcanic features in the area. There's a known, major, active rift valley between West and East Antarctica, and rift valleys in other parts of the world display different types of volcanism than you see from Mt. Vesuvius or Kilauea. West Antarctica is currently moving away from East Antarctica at 2mm per year, or 500,000 years per kilometer (0.62 miles). It's not exactly sprinting, but it's definitely moving.

VolcanoesFrom Here's why the study is sobering: There are signs that at least some of these volcanoes have erupted, even with Antarctica frozen solid. That's impressive in and of itself. Without wanting to oversimplify volcanism, there's a relationship to the amount of pressure inside the magma chamber below a volcano and the weight and pressure of whatever's above it. A mile of ice is very heavy, but it's not as heavy as a mile of rock. And the melting point of water, even under high pressure, is far below the temperature of your average magma.

The world is still rebounding from the last ice age

Most people are aware that continents break apart, move together, and break apart again over a span of hundreds of millions of years. Less discussed is the impact ice ages have on the height of continents. The sheer weight of all the ice forces continents downwards. As the ice melts, the land rebounds. This is called isostatic rebound, or glacial rebound, and you can see evidence of it at the Bathurst Inlet, Nunavut. Those lines on the shore aren't sand; the inlet receives little to no tide. That's where the beach used to be, with each line higher on the shore corresponding to a lower height of the land.

1200px-Rebounding_beach,_among_other_things_(9404384095)Image courtesy of Wikipedia

Currently, Antarctica is believed to have sunk by almost 3,000 feet thanks to the sheer weight of the ice sheet on top of it. Inland Greenland, for comparison, is believed to have sunk by just under 2,000 feet in some areas. We think of Antarctica as a monolithic field of white, thanks to its depiction on most maps, but were the ice sheet removed, it would look something more like this:

Antarctica-IfNow

In the very long term, Antarctica would rebound, leading to a map more like this:

Antarctica_Without_Ice_Sheet

But before we get there, there's a minor issue to be dealt with first. Due to global warming, some parts of Antarctica are warming faster than others -- or, to be a bit more specific about it, the area with all the volcanoes is melting faster than any of the others.

AntarcticaTemps_1957-2006Image by NASA

Research in Iceland has shown that a reduction in ice sheet thickness has an impact on activity in the mantle below volcanos. Again, this makes sense. The less heavy the weight, the easier it is for magma to erupt. The study authors aren't sure if the prevalence of volcanic cones would accelerate ice sheet melting (through eruption) or actually help to stabilize the ice sheet by providing a barrier to ice sheet movement.

Either way, magma upwelling underneath the glacier will melt some amount of ice -- and there's some evidence to suggest that one or more hotspots may exist under Western Antarctica, similar to the hotspot beneath Hawaii. Ice sheets are absolutely capable of flowing and using water as a lubricant. And we know there's liquid water under the ice already, thanks to research into Lake Vostok.

A surge in volcanic activity within one of these rifts could lead to ice melt and accelerate ice melting on the continent.

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Volcanoes Climate Eastern Antarctica Antarctica Erebus

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