Deep in the Earth, an engine is churning and causing earthquakes, volcano eruptions and other changes at the surface, according to a Canadian study.

Scientists at the University of Toronto and the University of Western Ontario have developed a model of how the Earth's interior is changing.

"In effect, we have found that the solid Earth is being churned by a four-piston heat engine with two immense sinking cold slabs and two equally large rising hot plumes," said lead author Alessandro Forte of UWO.

Earthquakes could be caused by a heat engine deep within the planet
Earthquakes could be caused by a heat engine deep within the planet

The model of the Earth's mantle flow and structure builds on the plate tectonic theory proposed in the 1960s. It suggests the Earth's crust is split into a few huge plates that constantly shift to produce earthquakes.

But plate tectonics doesn't explain how movements deep within the Earth are linked to what moves at the surface.

The first clues came from research done in the 1980s, which provided the first images of the Earth's internal structure. The images showed areas under the Earth's surface below the edges of the Pacific Ocean where earthquake waves travelled faster than at other areas.

Quito volcano eruption in 1999
Quito volcano eruption in 1999

Earth scientists had thought the slower-moving regions were immense blobs of material that have remained pretty much unchanged since the Earth formed.

But the new model shows the giant blobs actually float up to the surface and add to the ebb and flow in the Earth's mantle.

It has been described as the most unified model on the Earth's dynamics to date. The model could help scientists understand long-term changes in sea levels, topography and climate on Earth, as well as other planets.

The study appears in the April 26 issue of Nature.