Researchers at the University of Bristol reveal today in the journal Nature that they have developed a seismological ‘speed gun‘ for the inside of the Earth. Using this technique they will be able to measure the way the Earth’s deep interior slowly moves around. This mantle motion is what controls the location of our continents and oceans, and where the tectonic plates collide to shake the surface we live on. For 2,900 km (1800 miles) beneath our feet, the Earth is made of the rocky mantle. Although solid, it is so hot that it can flow like putty over millions of years. It is heated from below, so that it circulates like water on a stove. While geophysicists know something about how the material moves by the time it reaches the top of the mantle, what goes on at the bottom is still a puzzle. However researchers need to know both to predict how the Earth’s surface—our home—will behave.
This enigmatic part of the Earth is known as D″ (pronounced ‘dee-double-prime’). Dr James Wookey said: “We believe that D″ is made from crystals which line up in a certain orientation when the mantle flows. We can measure how they line up, and in this study we do this for one part of the world – North and Central America. In the future our method can then be used to see which direction the mantle is moving everywhere.”