Privileged Planet: how continents were formed (Introduction)

by David Turell , Friday, August 12, 2022, 18:54 (633 days ago) @ David Turell

From meteorites:

https://www.sciencealert.com/the-continents-were-created-on-early-earth-by-giant-meteor...

"To date, Earth is the only planet we know of that has continents.

"Exactly how they formed and evolved is unclear, but we do know – because the edges of continents thousands of miles apart match up – that, at one time long ago, Earth's landmass was concentrated in one big supercontinent.

"Since that's not what the planet looks like today, something must have triggered that supercontinent to break apart. Now, we have new evidence to suggest that giant meteorite impacts played a significant role.

"The smoking gun consists of crystals of the mineral zircon, excavated from a craton in Western Australia, a piece of Earth's crust that has remained stable for over a billion years.

"Known as the Pilbara Craton, it is the best-preserved chunk of crust on the planet… and the zircon crystals within it contain evidence of ancient meteorite impacts before the continents broke apart.

"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," explained geologist Tim Johnson of Curtin University in Australia.

"'Our research provides the first solid evidence that the processes that ultimately formed the continents began with giant meteorite impacts, similar to those responsible for the extinction of the dinosaurs, but which occurred billions of years earlier.'"

***

"However, many meteorites have pelted Earth in eons past, in numbers much higher than the number of continents. It's only the largest impacts that could generate enough heat to create the cratons, which appear to be twice as thick as their surrounding lithosphere.

"These findings are consistent with previously proposed models for the formation of cratons around the world – but constitute, the researchers said, the strongest evidence yet for the theory.

Comment: having continents and oceans prepared the Earth for life. All naturally appearing contingencies or design? I'll stick with a designer.