The Earth's Mantle Was Much Hotter Than It Is Today, Study

According to a new study, the Earth's mantle was much hotter once than it is today. Also, during the Archean eon, the Earth's crust was very unstable and "dripped" down into the mantle.

Temperatures during the Archean eon 4 million years ago were so high that the Earth's crust simply melted back into the mantle. This discovery offers a new insight of how the Earth's crust evolved since the Archaean eon, according to a press release.

For this new study, Tim Johnson, from the Institute of Geosciences at Johannes Gutenberg University Mainz (JGU, analyzed the evolution pattern of the Earth's crust since the Archean eon. According to him, the dense primary crust went to the mantle in drip form in a vertical pattern, according to HNGN. This is the opposite of how the tectonic plates move today in which the pattern is mostly lateral which allows it to hit the oceanic crust. When tectonic plates meet with the oceanic crust, subduction zones are formed.

The team used thermodynamic calculations and latest computer models that simulated Earth's early days to come to their conclusion that "mineral assemblages that formed at the base of a 45-kilometer-thick magnesium-rich crust were denser than the underlying mantle layer," the news release reported.

The computer model showed that a super-thick and magnesium-rich crust would have become unstable in heat above 1,500 to 1,550 degrees Celsius. This would have caused the crust to sink in a phenomenon dubbed 'delamination'.

"The dense crust would have dripped down into the mantle, triggering a return flow of mantle material from the asthenosphere that would have melted to form new primary crust," the news release reported.

"The findings add to our understanding of how cratons and plate tectonics, and thus also Earth's current continents, came into being," Johnson said in a press release.