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View of Earth as seen by the Apollo 17 crew traveling toward the moon.

Earth is structured sort of like an onion – it’s one layer after another.

Starting from the top down, there’s the crust, which includes the surface you walk on; then farther down, the mantle, mostly solid rock; then even deeper, the outer core, made of liquid iron; and finally the inner core, made of solid iron and with a radius that’s 70% the size of the moon’s. The deeper you dive, the hotter it gets – parts of the core are as hot as the surface of the sun.

Shichun Huang, an associate professor of earth and planetary sciences at the University of Tennessee, Knoxville, studies the insides of the planet. Just as a doctor uses sonography to capture images of the structures inside your body with ultrasound waves, geoscientists use seismic waves – sound waves produced by earthquakes — to image Earth’s internal structures. Read the full article on The Conversation.

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Lindsey Owen McBee (865-974-6375,