Research News

Bringing magma up to our feet in Antarctica

Carbon dioxide underground helps magma avoid being trapped deep in the Earth

Antarctica has long been a land of mystery and heroic feats made famous by the explorations of James Ross and Roald Amundsen, Robert Scott and Ernest Shackleton.  

A key piece of the puzzle for understanding global continental evolution, Antarctica is home to examples that define the spectrum of Earth's volcanic processes. Now, a new study shows that carbon dioxide (CO2) deep underground helps magma avoid being trapped deep in the Earth and allows it to reach and pool at the surface. 

The study, published in Nature Communications, "expands our understanding of the sources and transport of diverse types of magma and volatile gases to the surface," says Phil Wannamaker, a study co-author and a geophysicist at the University of Utah. The study was funded in part by the U.S. National Science Foundation

Mount Erebus is Antarctica's only active volcano. It and its dormant companion volcano, Mount Terror, were named after the exploring ships of Ross, who discovered the volcanoes and the Transantarctic Mountains in 1841.  

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

Erebus is in a continental rift zone. Continental rifting happens as Earth's crust and mantle are pulled apart. The magmas in the rift zone have volatiles from the recycling of ocean crust and sediments, but these are much older and are liberated to the surface through the rifting process. Instead of water, the volatiles in these magmas are CO2-dominated. 

Erebus also has a lava lake, a classic feature of an evolved, CO2-rich rift volcano. Lava lakes show that there's something about rift volcanoes that allows magma to reach the surface relatively peacefully. 

Data obtained by the scientists show a steep conduit in the upper mantle, the magma source. The conduit takes a pronounced lateral turn in the deep crust before reaching shallower magmatic storage and the summit lava lake. "We interpret the lateral turn to represent a structural 'fault-valve' controlling episodic flow of magma and CO2 gases, which replenish and heat the high-level phonolite magma evolution chamber," Wannamaker says. Phonolite is the rock type formed by Erebus' magma. 

"This study using natural time variations of the Earth's magnetic and electric fields provides a look at deep magmatic system processes from the mantle source to the surface under Mount Erebus," says Michael Jackson, a program director in NSF's Office of Polar Programs.