How did continents form? Giant meteorite impacts could be responsible, says study

Source: The post is based on the article “How did continents form? Giant meteorite impacts could be responsible, says study” published in Down To Earth on 11th August 2022.

What is the News?

According to a study published in The Nature journal, giant meteorite impacts could be responsible for the formation of continents on Earth.

What is the current theory on the formation of continents?

The most commonly accepted theory currently in place attributes continent formation to the movement of tectonic plates (as per the Plate Tectonics Theory).

What is the alternative theory on the formation of continents?

There is a theory that the continents were formed by giant meteorite impacts. But there was little solid evidence for its support.

Note: Meteorite impacts generated massive energy to form oceanic plates which later evolved into continents.

Now the researchers have found the most robust evidence showing that Earth’s continents were formed by giant meteorite impact.

What is the evidence researchers have found?

Zircon crystals in Pilbara Craton: The researchers looked for evidence in zircon crystals embedded in rocks from the Pilbara Craton in Western Australia. This craton is the remnant of an ancient crust that began forming more than three billion years ago.

Note: A craton is an old and stable part of the continental lithosphere, which consists of Earth’s two topmost layers, the crust and the uppermost mantle.

– Zircons are formed by the crystallization of magma or are found in metamorphic rocks. They act as tiny time capsules, recording the period of geologic activity. Newer zircon adds to the original crystal as time progresses.

Findings: By studying the composition of oxygen isotopes in these zircon crystals, the researchers have found a ‘top-down’ process starting with the melting of rocks near the surface and progressing deeper, consistent with the geological effect of giant meteorite impacts.

What is the significance of this study?

Understanding the formation and ongoing evolution of the Earth’s continents is crucial given that these landmasses host the majority of Earth’s biomass, all humans and nearly all of the planet’s important mineral deposits.