The earliest evidence of plate tectonic activity can be found in the tiny crystals of zircon.
When the edge of one plate slips beneath the edge of another plate, there are specific conditions that cause the formation of elements in the crystals. New constraints on when plate tectonics emerged on Earth are provided by this.
Understanding how plate tectonics changed the composition of the oceans and atmosphere is important for understanding how we got here and what makes a planet hospitable.
It is difficult to understand the geology of early Earth. The only direct record of the Hadean eon can be found in the crystals of the mineral zircon.
The ancient grains, three or fewer in most locations, seem to survive the ravages of time but rarely.
An amazing treasure was unearthed recently by a team of geologists. The ancient block of Earth's crust was found in the Barberton Greenstone Belt in South Africa, and contained a chronological series of 33 tiny zircon crystals.
The series gave a rare opportunity to look at the changing conditions of early Earth, from the Hadean through the Eoarchaeon era, which lasted from 4 to 3.6 billion years ago.
Mineral crystals can act as a sort of time capsule that contains information about the conditions in which they formed, and zircon crystals in particular can be extremely valuable for this scientific purpose. The rocks from which the metal hafnium and trace elements are found can be used to make inferences.
The team of scientists studied the Greenstone Belt zircons to reconstruct the conditions under which they formed. They found that the crystals were similar to rocks that were formed at the edges of tectonic plates.
The researchers think that plate tectonics were active at the time of the crystals.
When I say plate tectonics, I mean an arcs setting, where one plate goes under another and you have all that volcanism, like the Ring of Fire.
At 3.8 billion years ago, there was a dramatic shift in the structure of the planet, with new rocks forming and more and more similar to what we see today in plate tectonics.
The zircon crystals that were 3.8 billion years old were not formed in a subduction zone, but in a Hadeanprotocrust that formed from remelted mantle material.
The team compared their findings to zircon crystals from around the world to make sure they were not just observing a local phenomenon. Similar transitions were shown by the other zircons.
It is difficult to know if the tiny grains point to the evolution of our world towards plate tectonics, but the results definitely suggest that a global change was occurring.
Drabon said that there was evidence for a significant change on the Earth around 3.8 to 3.6 billion years ago.
The record we have for the earliest Earth is limited, but seeing a similar transition in so many different places makes it possible that it was a global change in crustal processes. There was reorganization happening on Earth.
AGU Advances has published the research.
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