How to See the Earth's Core

The Earth's core is not directly accessible to scientists, so they've been forced to ingeniously develop a variety of novel approaches to glean information about the churning hot center of our planet.

Journey to the Center of the Earth

First let's refresh on what we do know about the individual layers of differentiation lying beneath our feet. Traveling down through the crust of the Earth, the first major boundary we reach is the Mohorovicic (Moho) discontinuity, past which we're now in the mantle.

Researchers have been attempting to penetrate the Moho for a number of years, and another effort is currently underway. One of the objectives of the Integrated Ocean Drilling Programme (IODP) is to drill through the planet's crust by tunneling through the ocean floor.

According to Paul Parsons of the Telegraph, "The IODP has already reached the lower part of the crust, by drilling at a part of the Atlantic where it is at its thinnest, and the researchers hope to breach the mantle by 2012." Admirable as this effort is, and despite the wealth of knowledge that can be garnered from it, we will be leaving the IODP researchers wildly far behind as we continue to the core.

After we pass through the mantle -- no small task considering about 83 percent of the Earth's volume is contained within it -- we reach the core. This isn't some little nugget cuddled in the center of the planet either; the core is approximately equal to the size of Mars.

Split into two portions, the outer core -- likely a molten layer of liquid iron with some additional elements thrown into the mix -- surrounds the inner core, which is basically a super-hot solid hub of metallic elements, also primarily iron. But if the mantle contains most of the earth's volume, the combined cores take the cake in terms of mass: about 67 percent of the planet's mass lurks within its ultra-dense center.

Studying Seismic Waves

Probably the most well-known method for peering into the depths of the planet is through the use of seismic waves. Measuring the wave patterns that shoot through the Earth when an earthquake strikes helps to distinguish between the various layers buried far below.

This happens because the shock waves travel at different speeds through different mediums. They move quickly through rocks, for example, but more slowly through fluids, and passing from one substance to the next can also deflect the direction of their paths. In some cases, the waves won't penetrate a certain material at all, creating shadow zones around the globe.

Satellite Imagery and Magnetic Fields

Another way scientists can learn about the Earth's core is by measuring fluctuations in the planet's magnetic field. That's because one of the major factors affecting the magnetosphere is the convective motion of all that swirling molten liquid thousands of miles below the surface of the earth.

So by studying the alterations in intensity of the earth's magnetic field, researchers have been able to get a better understanding of the attributes of the Earth's core.

"What is so surprising is that rapid, almost sudden, changes take place in the Earth's magnetic field," says Nils Olsen, senior scientist with DTU Space, a department of the Technical University of Denmark. "This suggests that similar sudden changes take place in the movement of the liquid metal deep inside the Earth which is the reason for the Earth's magnetic field."

Olsen was lead author of a study published by Nature Geoscience in May of 2008, in which satellite data collected over nine years was used to study the planet's magnetic field. The findings concluded that it could be altered in as little as a few months time.

Article posted April 6, 2009.

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