ARTICLES
How Earth’s Continents became twisted and contorted over millions of years (continued)
Fifty years after the plate tectonic revolution, we are pretty sure
the continental parts of plates are not uniform, nor are they rigid.
The giant forces that slowly move continents across the viscous
mantle layer underneath, like biscuits gliding over a warm toffee
ocean, stress the continents, and twist and contort the crust. This
is a process that has taken place over millions of years.
As part of recent research, we worked with a team of international
collaborators to build a computer model to show just how much
the continents have been deformed since the Triassic Period,
about 250 million years ago. The supercontinent Pangea
began breaking apart soon after, ripping along the seams
between Africa and North America [ https://www.youtube.com/
watch?v=uLahVJNnoZ4 ]
Immense forces
We already knew that that colossal tectonic forces act along
plate boundaries. We can see this when continents collide, such
as when Africa collided with Eurasia, forming mountains like the
Alps, or forming basins when continents are torn apart, as is
happening in East Africa.
The animation shows the motion of the tectonic plates and the
associated evolution of deformation since the breakup of the
Pangea supercontinent (Credit: Sabin Zahirovic).
We detail this understanding of continent mangling in a paper
published in the journal Tectonics this month.
A model of tectonic plates moving over the viscous mantle.
Blue material represents plates that are being recycled into
the hot interior of the Earth. Red material represents extra
hot material rising from the Earth’s core. Credit: Maelis
Arnould, [ see
https://agupubs.onlinelibrary.wiley.com/doi/
abs/10.1029/2018GC007516 ]
Folded marine sediments in the Alps (Helvetic Nappes of
Switzerland), uplifted and deformed by the collision of the
African and Eurasian continents.
Our new research used geological and geophysical data to
pinpoint all major zones of continental deformation, built into a
global model of plate motions using our GPlates software.
We show that at least one third of all continental crust has been
massively deformed since Pangea first started breaking up.
That’s a whopping 75 million km2, roughly the size of North and
South America and Africa combined.
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SCIENCE EDUCATIONAL NEWS VOL 68 NO 3