Submitted by: Odio @ 08:35 PM | Wednesday, December 14, 2016 | (url: http://www.scienc...)
If you looked back at Earth 170 million years ago, youd find a very different planet. The worlds continents were all linked up into one vast 'supercontinent' called Pangaea, and according to a new study, the outermost layer of the planet was 1.7 km (1 mile) thicker than it is today.
Researchers have found that since the break-up of Pangaea, Earths inner mantle has been cooling twice as fast as we thought, and it looks like its crust has been thinning out ever since.
"Its important to note [that] Earth seems to be cooling a lot faster now than it has been over its lifetime," says geophysicist Van Avendonk from the University of Texas.
"The current state of Earth, where we have a lot of plate tectonic events, this allows Earth to cool much more efficiently than it did in the past."
To be clear, when we say Earth has been cooling at an unprecedented rate over the past 170 million years, were not talking about the climate, which has definitely not been cooling.
What Avendonk and his team have been investigating is the international temperatures of Earth over time, and theyve found that the planet today is producing far less magma than it was during the time of the dinosaurs.
To trace the changes in Earths outer layer over the past 2.5 billion years, they analysed 234 measurements of crust thickness from around the world over a number of geological ages.
They found that oceanic crust formed in the mid-Jurassic 170 million years ago was 1.7 km (1 mile) thicker than the crust thats being produced today, and since then, the mantle below has been cooling much more rapidly than expected.
So why is Earths crust thinning out?
The outermost crust of Earth is formed by the mantle, which sits between the scorching hot core and the crust, spanning some 2,900 km (1,802 miles), and making up a whopping 84 percent of the planet's total volume.
Magma produced in the mantle forms the outer oceanic crust when it rises to the surface and cools into rock.