Ever wondered what Earth might have looked like billions of years ago? Well, it could have been chilling under the Pacific Ocean and some far-flung corners of South Africa. The finding may flip our understanding of Earth’s geological history on its head.
The highveld of South Africa was made famous first by the puzzlement of scientists about the Barberton Greenstone Belt. It hosts some rock formations totally at variance with what we feel we understand about the early Earth. Picture this: lovely crystals of barite from shallow waters mixed with volcanic rock, chert, sandstone, and conglomerate that belong deep underwater. It is a geological jumble that puzzled experts for years.
Now a team of researchers headed by geophysicist Simon Lamb and Cornel de Ronde is believed to have cracked the code because they made comparisons between ancient rocks in South Africa with much younger rocks laid down on the sea floor off the coast of New Zealand. These New Zealand rocks, of an age of about 20 million years, were deposited near the Hikurangi subduction zone, in which the Pacific tectonic plate goes under another plate, causing large and very frequent earthquakes.
He’s where it gets extremely interesting. Taking a leap forward, these scientists advanced the supposition that early Earth wasn’t such a calm, earthquake-free place as people thought. Instead, it was shaken by colossal earthquakes, as tectonic plates slid beneath each other in subduction zones similar to those going on in New Zealand today. It was pointed out that Lamb and de Ronde indicated that the nature of rock formations within the Barberton Greenstone Belt is broadly consistent with what emerges from underwater landslides in the Hikurangi subduction zone, where sediment layers from both land and the deep ocean get mixed up by earthquakes.
It’s a new perspective that could change everything we thought we knew about early Earth. Citing, “We argue that the widely held view of the early Earth as a hotter place, free of earthquakes and with a surface so weak it was unable to form rigid plates is wrong.” In other words, much like what we see today, the young Earth has undergone similar tectonic activities, complete with large-scale earthquakes and related geologic chaos.
That’s not all, however. Subduction zones are also a site for explosive volcanic eruptions. Remember the absolutely colossal eruption of the Hunga Tonga-Hunga Ha’apai volcano of Tonga back in January 2022? It launched a cloud of ash into space and set off more than 200,000 strokes of lightning. Also part of this area are submarine volcanoes that are erupting a very rare type of lava called boninite, which is akin to lava that was commonplace on the young Earth.
The volcanic-ash-filled Barberton Greenstone Belt speaks eloquently of ancient volcanic eruptions as violent and large-scale as we see today. Indeed, the team speculates that the necessary lightning strokes produced by these eruptions could have been the spark for life itself to create the basic organic molecules necessary for life to form.
That’s even more exciting because it holds clues to our planet’s tumultuous past and probably of life itself. Indeed, as Lamb and de Ronde so fittingly put it, “Deep in the south-west Pacific are hidden echoes of our planet not long after it was created. They provide unexpected clues about the origins of the world we know today, and possibly life itself.”
Next time you take a glance through a map or any other document and you see the Pacific Ocean, that tame and quiet part of the earth’s surface, remember the record of violence and dynamism of Earth’s past hidden beneath its waves. Who knows what other secrets are yet to be laid bare?
