Giant asteroids created the continents on Earth?
Earth is the only planet we know of with continents, the giant landmasses that provide homes to humankind and most of Earth's biomass. However, we still don't have firm answers to some basic questions about continents: how did they come to be, and why did they form where they did? One theory is that they were formed by giant asteroids crashing into Earth's crust long ago. This idea has been proposed several times, but until now there has been little evidence to support it.
In new research published in Nature, we studied ancient minerals from Western Australia and found tantalising clues suggesting the giant impact hypothesis might be right.
The continents form part of the lithosphere, the rigid rocky outer shell of Earth made up of ocean floors and the continents, of which the uppermost layer is the crust.
The crust beneath the oceans is thin and made of dark, dense basaltic rock which contains only a little silica. By contrast, the continental crust is thick and mostly consists of granite, a less dense, pale-coloured, silica-rich rock that makes the continents “float”.
Beneath the lithosphere sits a thick, slowly flowing mass of almost-molten rock, which sits near the top of the mantle, the layer of Earth between the crust and the core.
If part of the lithosphere is removed, the mantle beneath it will melt as the pressure from above is released. And impacts from giant meteorites – rocks from space tens or hundreds of kilometres across – are an extremely efficient way of doing exactly that!
Giant impacts blast out huge volumes of material almost instantaneously. Rocks near the surface will melt for hundreds of kilometres or more around the impact site. The impact also releases pressure on the mantle below, causing it to melt
Read more on tech.hindustantimes.com
