Emily Chan
Geologists have discovered remnants of Earth’s mantle that have persisted for over 2.5 billion years. The ancient rocks were less oxidized than modern ones, indicating that they were exposed to extreme heat.
This discovery provides new insights into the geological history of our planet, challenging previously held beliefs about Earth’s oxidation processes and offering a peek into the past.
Earth’s mantle, the outer crust of our planet, is made up of different layers that consist of different types of rock. One of the most common types is an igneous rock high in silica content called peridotite.
In the past, when geologists compared prehistoric peridotite from Earth’s mantle with modern samples, they detected a major discrepancy.
Exposure to oxygen causes some of the rock to change through a process known as oxidation. The ancient remnants from Earth’s mantle were a lot less oxidized than samples from the modern mantle.
That means something must have changed between now and the Archean Eon, which was over 2.5 billion years ago.
Experts have proposed that changes in Earth’s oxygen may have led to the shift. Possibly, a large increase in oxygen resulted in greater oxidation.
However, new clues suggest that the oxidation change was caused by Earth’s mantle rocks being melted in extreme heat and lasting throughout billions of years.
The rocks were extracted from two spots—the Southwest Indian Ridge between southern Africa and Antarctica and the Gakkel Ridge near the North Pole.
Sign up for Chip Chick’s newsletter and get stories like this delivered to your inbox.
