Continents on Ancient Earth Were Created by Giant Meteorite Impacts, Scientists Find




The only planet we are aware of with continents is Earth.

Uncertainty surrounds their formation and evolution, but we do know that the Earth's landmass was originally mostly contained within a single large supercontinent since the margins of continents that are hundreds of miles distant coincide.

The planet does not now resemble that, thus something must have caused that supercontinent to disintegrate. Now, fresh data point to a crucial role for massive meteorite strikes.

Zircon crystals that were discovered in a Western Australian craton, a portion of the Earth's crust that hasn't changed in more than a billion years, are the smoking gun.

The Pilbara Craton is the world's best-preserved fragment of crust. and it contains evidence of old meteorite strikes before the continents split apart in the form of zircon crystals.

According to geologist Tim Johnson of Curtin University in Australia, "studying the composition of oxygen isotopes in these zircon crystals revealed 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."

Our discovery offers the first convincing evidence that the mechanisms that eventually gave rise to the continents started with massive meteorite strikes that happened billions of years earlier than those that caused the extinction of the dinosaurs.

26 rock samples with zircon particles that range in age from 3.6 to 2.9 billion years old were used for the research.

The oxygen isotopes oxygen-18 and oxygen-16, which contain 10 and 8 neutrons, respectively, were closely examined by the study team. In paleogeology, these ratios are used to establish the temperature at which the rock in which the isotopes are discovered was formed.

The team was able to identify three different and crucial phases in the formation and development of the Pilbara Craton based on these ratios.

The creation of a significant amount of zircons, which is compatible with partial melting of the crust, is the first step. The researchers demonstrate that this partial melting was probably caused by meteorite bombardment, which heated the planetary crust upon impact.

According to the team's view, the craton was formed as a consequence of a single, enormous impact that produced the earliest cluster of these zircons.

The crustal nucleus underwent reworking and stability during the second stage, and then underwent melting and granite production during the third stage. Much later, this solidified nucleus would change into the continents we know today, just like the cratons discovered on other continents across the globe.

The number of meteorites that have struck Earth over the ages is substantially more than the number of continents. Only the most powerful impacts could provide enough heat to form the cratons, which seem to be twice as thick as the lithosphere around them.

These results support previously put out theories for how cratons are formed around the world, but they also provide, according to the researchers, the greatest evidence yet for the idea.

Out of about 35 known cratons, it is just one. The researchers will need to compare its findings with further samples from various cratons to determine if their model is universally consistent in order to strengthen the case even further.

According to Johnson, patterns in old continental crust from other parts of the world appear to follow those seen in Western Australia. In order to determine whether our model is more broadly applicable as we believe, we would like to test our findings on these ancient rocks.


The research has been published in Nature.

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