Apparently, meteorite impacts lead to forming our oldest rocks


When meteorites hit our Earth, they brought extreme temperatures with each impact. That’s how some of the oldest rocks from our planet might have formed.

Examples, please

Let’s take, for example, the granite-like felsic rocks. The ones found in the northwestern part of Canada come from the Earth earliest era and they differ from the ones found at the center of the continents. The difference in composition could be explained by meteor impacts, according to new computer modeling.

After it formed, sometime between 4.6 and 4 billion years ago, the Earth went through the Hadean era. It was a hellish time because a high flux of meteorites impacted the planet. Scientists believe that the predominant mechanism of generating the Hadean felsic rocks resulted through impact melting.

What are these rocks?

These rocks that we are talking about come from 4.02 billion years ago. They are called Idiwhaa gneisses and they can be found in the Acasta Gneiss Complex of Northern Canada. They display a composition that is totally different from the tonalite-trondhjemite-granodiorite rocks which are scattered across the oldest parts of the continent.

This means that the Idiwhaa have a lower concentration of silica and there are more iron molecules embedded in their structure.

Why do they differ?

First, the age is a clear indicator that the Idiwhaa came from the same time that the Earth was bombarded by meteorites. Of course, this isn’t the only reason. Scientists measured the rocks’ properties. We are talking about their pressure, temperature, composition and how much did they need to melt in order to take form.

Through the use of computer simulation, they were able to observe the impact of a 10 km-wide meteorite hitting a mafic crust (rocks that resemble basalt) with a speed of 12-17 km/s. 10-50 km from the point of impact and at depths of about 3 km, the ideal conditions were met so that these rocks could be formed.


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