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Big moves

By David, 17 February 2022 News

Light shining over the edge of planet Earth

Cosmic forces might be moving the continents on Earth!
Image: tectonics2.jpg

By Louise Molloy

The crust under your feet – it’s on the move! But we’re not talking about the edge of your toast. This crust is the outer layer of our planet.

The Earth’s crust has been on the move for millions, and even billions, of years. There’s an exciting new theory looking at why – and Pluto might hold the answer.

Tectonic whatsy?

Coloured map of tectonic plates

Earth’s crust is broken up into many plates
Credit: USGS

The crust covers Earth in a jigsaw of giant slabs of rock called tectonic plates. They sit on top of the mantle, a layer of hot rock that’s thousands of kilometres thick. The mantle is made of solid rock. But since it’s really hot and under extreme pressure, it can flow or creep very slowly. The mantle is being heated by the extreme temperatures of the core at the centre of Earth.

Tectonic plates move about 2 to 10 centimetres a year. This mostly makes for very very slow change. But when two plates collide, it can make for some impressive mountains, including Mount Everest!

Hot moves

Back to Earth’s core and the incredible amount of heat it releases. Scientists have thought it’s the energy from this heat that moves the tectonic plates. But how?

The heat from the core transfers into the mantle’s flowing rocks. Hotter material is less dense than the cooler material above so it moves upwards, losing heat as it goes. Then as it cools, it drops back towards the core.

This process is called convection. It can be seen in pots of water on the stove, in ocean currents and in big weather patterns. But is convection strong enough to move the tectonic plates? Some scientists question this theory.

To Pluto

Pluto and its moon Charon

Pluto is only a bit bigger than its moon Charon
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Professor Anne Hofmeister from Washington University argues that something else is moving the continents.

She’s looking at the forces of gravity between the Sun, Moon and Earth. In this theory, it’s the interplay of these forces, as well as Earth’s daily spin, that make the tectonic plates move.

So how do we work out which theory is right? Anne has one idea that is literally out of this world.

“One test would be a detailed examination of the tectonics of Pluto,” says Anne. “It is too small and cold to convect, but has a giant moon and a surprisingly young surface.”

Pluto’s young surface might come from moving plates. And proving that would be a big support for Anne’s theory.

Stay tuned as scientists continue to investigate!

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