Earthquakes reveal the planet's temperature

 Scientists have taken the temperature of the Earth’s internal structure finding it to be a white-hot 3700?C – But rather than a thermometer, it was earthquake-generated seismic waves that proved to be the ideal tool for the job.

 Using data from thousands of earthquakes recorded at more than 1000 seismic observatories, an interdisciplinary team of earth scientists and mineral physicists from the US have adapted technology developed for exploration of oil and gas to image the core-mantle boundary 1800 miles beneath the Earth’s surface.

“Rather than depth, it’s the resolution and lateral scale that are unique in this work,” said study leader Rob van der Hilst, director of MIT’s Earth Resources Laboratory. “This could lead to a new era in seismology and all the other deep Earth sciences. In addition, our new expertise may be able to improve how we look for oil in or beneath geologically complex structures such as the Gulf of Mexico salt domes,” he said.

The technique - akin to medical imaging such as ultrasounds and CAT scans - has led to detailed new images of the boundary between the Earth’s core and mantle.

It is the speed of the seismic waves that indicates the chemical and physical properties of the material they encounter. By combining this seismic data with mineral physics, the team calculated the temperature at this boundary as well as above and below it.

The images should help researchers better understand how and where the Earth’s internal heat is produced and how it is transported to the surface. They also provide insight into the Earth’s giant heat engine - a constant cycle of heat production, heat transfer and cooling.

“The heat flow that we measure is larger than what is needed to drive the geo-dynamo, so there is actually more energy down there than people thought,” van der Hilst said.