There is something mysterious and hot lurking beneath the surface of the Antarctic ice.

Now Nasa says that it might have found the source of that strange heating - a "mantle plume" - or upwelling of abnormally hot rock, that lies deep beneath the surface.

The heat is causing the surface of the ice to melt and crack, resulting in rivers and other disruption to Antarctica.

Around 30 years ago, a scientist at the University of Colorado Denver said that there . might be a mantle plume under a region of the continent known as Marie Byrd Land. That hypothesis helped explain some strange features seen on the ice, like volcanic activity and a dome.

Mantle plumes are narrow streams through which hot rock rises up from the Earth's mantle, and then spreads out under the crust. Because the material itself is hot

and buoyant, it makes the crust bulge upwards.

They explain how some places - like Hawaii and Yellowstone - have huge amounts of geothermal activity despite being far from the edge of a tectonic plate.

But it was also an idea that was hard to believe, since the ice above the plume is still there. "I thought it was g crazy," said Helene Seroussi of Nasa's Jet Propulsion Laboratory, who helped the lead work. "I didn't see how we could have that amount ofheat and still haveiceontopofit."

Now scientists have used the latest techniques to support the idea. The team developed a mantle plume numerical model to look at how much geothermal heat would be needed to explain what is seen at Marie Byrd Land, including the dome and the giant subsurface rivers and lakes present on Antarctica's bedrock.