Ancient asteroid impacts played a role in creation of Earth's future continents

[Judi Lynn]

by HeritageDaily January 31, 2019

The heavy bombardment of terrestrial planets by asteroids from space has contributed to the formation of the early evolved crust on Earth that later gave rise to continents – home to human civilisation.

More than 3.8 billion years ago, in a time period called the Hadean eon, our planet Earth was constantly bombarded by asteroids, which caused the large-scale melting of its surface rocks. Most of these surface rocks were basalts, and the asteroid impacts produced large pools of superheated impact melt of such composition. These basaltic pools were tens of kilometres thick, and thousands of kilometres in diameter.

“If you want to get an idea of what the surface of Earth looked like at that time, you can just look at the surface of the Moon which is covered by a vast amount of large impact craters,” says Professor Rais Latypov from the School of Geosciences of the University of the Witwatersrand in South Africa.

The subsequent fate of these ancient, giant melt sheet remains, however, highly debatable. It has been argued that, on cooling, they may have crystallized back into magmatic bodies of the same, broadly basaltic composition. In this scenario, asteroid impacts are supposed to play no role in the formation of the Earth’s early evolved crust.

More:
https://www.heritagedaily.com/2019/01/ancient-asteroid-impacts-played-a-role-in-creation-of-earths-future-continents/122616

[lastlib]

1. I've often wondered if the Pacific Ocean isn't the result of some ancient collision....

I have no data to support it, it's just a thought.

[Igel]

2. Long before I was a kid there was this idea

that at some point the Earth was rotating quickly enough for a lump to form and then break away. That was how the Moon was supposedly formed. The idea seemed likely because of the fairly circular shape of the Pacific, where the Moon's matter was thought to have originally resided.

Since that time we've come up with plate tectonics for how the continents and crust move around, making the Pacific a sort of accident, and the Theia hypothesis for Moon formation. We can push "tectonic theory" a bit past the purely theoretical stage, even if details are still being worked out. The Theia hypothesis seems pretty good, even though there are quibbles about (if I recall correctly) oxygen isotope ratios. But you go back 4.5 billion years and there are bound to be some ambiguities.