Giant V-shaped ridges on the floor of the Atlantic Ocean are explained by a new theory developed by University of California, Davis, geologist Garrett Ito.

The V-shaped ridges, which are hundreds of miles long, lie across the Reykjanes ridge, a line running south from Iceland where the continental plates of America and Europe are slowly drifting apart. Geologists know that Iceland is a tectonic "hot spot" where molten rock rises toward the surface, but the origin of the V-shaped ridges had puzzled geologists since their discovery 30 years ago, Ito said.

Ito used a computer model to show that a pulsing plume of molten rock, like a slow motion lava lamp beneath Iceland, could account for the phenomenon. Deep in the earth, the rock contains water which makes it more fluid. As it rises to the surface, the rock begins to melt, forcing out the water and making it stiff, Ito said. This sets an upper boundary for the partially molten rock, forcing it to flow sideways.

"It's a bit like pouring batter onto a hot griddle. As it hits the griddle it sets, and has to run sideways," said UC Davis geologist Charles Lesher, who is not an author on the paper.

The blobs of partially molten rock then flow along the mid-Atlantic ridge, about 90 miles (145 kilometers) below the surface. The molten rock slowly percolates upwards and eventually reaches the surface, where it "freezes" into solid crust. As the ridge pulls apart, it draws out the ends of the "V."

"This provides an explanation for the V-shaped ridges that links the surface features to the Iceland hotspot," said Lesher.

The study was published in the June 7 issue of Nature.