Earth is made up of a solid inner core, surrounded by a liquid outer core, in turn covered by a thicker or more viscous mantle, and ultimately by the solid crust beneath our feet.
*Interview with Professor Gary A Glatzmaier at bottom
The magnetic field is generated by the motions of the liquid iron alloy in the outer core beneath Earth’s crust. These motions occur because the core is losing heat to the overlying solid mantle that extends up to the crust on which we live.
The mantle itself is also in motion. This mantle motion is responsible for the drifting of the continents at the surface – and also responsible for earthquakes, volcanoes, and temporal changes in the climate.
In the past decade or so, researchers have focused on three possible mechanisms driving earthquakes. One is variations in gravitational potential energy, another is changes in thickness of the Earth’s crust along the Intermountain Belt and the third is changes in strength of the lithosphere; that is, the crust and upper mantle.
“In continental interiors, we know little about the forces that drive the earthquake cycle,” says Utah State University geophysicist Tony Lowry. “We rely mostly on the history of past earthquakes to assess hazards. But, because seismic observations cover only a tiny fraction of the time between the largest earthquakes, we can easily miss important parts of the story.”
Using new seismic and GPS data available from the massive NSF-funded Earthscope array across the western United States, the researchers looked at these observations simultaneously and found some surprises. “We’ve explored various aspects of how and why rocks break and flow, but this is the first time we’ve recognized the importance of deep mantle flow,” says Lowry. “This developing model gives us a new tool for understanding what makes earthquakes tick.”
Professor Gary A Glatzmaier – Solar Physicist – Gary’s recent research has focused on the Earth’s core. He produced the first dynamically-consistent computer simulations of the geo-dynamo, the mechanism in the Earth’s fluid outer core that maintains the geomagnetic field. The simulations span several millions of years, using an average numerical time step of 15 days. At the surface of the model Earth, the simulated magnetic field has an intensity, an axial dipole dominated structure, and a westward drift of the non-dipolar structure that are all similar to the Earth’s.