LONDON Earthquakes, volcanoes, shifting continents and even climate change are driven by a type of heat engine working deep beneath the earth's surface, Canadian scientists said on Wednesday.

According to Reuters, they have developed a model of the inner workings of the earth that explains the mystery of how features on the surface of the planet are constantly changing because of what is happening way below.

"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 Alessandro Forte, of the University of Western Ontario.

The research reported in the science journal ***Nature*** by Forte and Jerry Mitrovica, of the University of Toronto, provides the best model so far of earth dynamics.

It could also be used to better understand other planets in our solar system such as Venus, Mars and Mercury.

"We have discovered something grandiose in size and yet remarkably simple and symmetric," Mitrovica said in a statement.

The model of the earth's mantle flow and structure builds on the plate tectonics theory formulated in the 1960s and work done in the 1980s when earthquake waves gave researchers images of the internal structure of the earth.

The 80s research showed areas under the earth's surface below the Pacific Ocean where earthquake waves traveled faster and other regions where they slowed down.

Scientists thought giant blobs of stagnant material slowed down the earthquake waves beneath the surface in the slower areas but the new model shows the giant blobs float up to the surface and contribute to the ebb and flow in the earth's mantle.

In a commentary on the research, Michael Manga of the University of California, Berkeley, described the research as the most comprehensive integrated study so far of mantle flow.

"The compositional variations and temperature anomalies mapped by Forte and Mitrovica, along with mantle flow, are snapshots of a dynamic earth," he said.