Billions of years ago, earth was a boiling cauldron

A new study of the chemical components of rocks led by researchers at Penn State and Columbia University provides the clearest evidence yet for how Earth”s continents became and remained so stable – and the key ingredient is heat. Credit: Jaydyn Isiminger / Penn State

doi.org/10.1038/s41561-025-01820-2
Credibility: 989
#Geology

Think of Earth as a blacksmith forging steel. To transform raw metal into something strong, you need to heat it until it almost melts, hammer it hard, and let the impurities escape.

That’s exactly what happened to the continents.

Rocks melted, plates collided, and the entire planet resembled an out-of-control furnace. But at some point, something changed: parts of the crust began to cool, harden, and form the stable continents we know today?the firm platforms where mountains grow, rivers flow, and life flourishes. Until now, no one quite understood *how* this happened. A new study from Penn State and Columbia University has just revealed the secret: extreme heat, above 900 C, deep within the crust.

The “fire” came from radioactive elements-uranium, thorium, and potassium-which, like live embers, released heat relentlessly.

If they remained trapped down there, the crust would never stop melting.

But when the temperature exceeded 900 C, these elements began to rise, carrying excess heat to the surface, like smoke escaping from a chimney.

As the heat dissipated, the lower part of the crust cooled, solidified, and became a hard base like tempered steel.

“Without removing this heat, everything turns to mush again,” explains Andrew Smye, a geologist at Penn State and leader of the study.

“Continents only become stable when they manage to *get rid* of the internal fire.”

The researchers reached this conclusion by analyzing rocks from the Alps, the southwestern United States, and data from around the world.

They separated samples that had undergone high temperatures (above 650 C) and ultra-high temperatures (above 900 C).

The pattern was clear: in the rocks that “cooked” at over 900 C, there was almost no uranium or thorium.

They had risen.

In the others, they were still there, trapping the heat.

To make their conclusions, the team sampled rocks from the Alps in Europe and the southwestern United States, as well as examined published data from the scientific literature. Here is a chemical analysis performed in Smye”s lab at Penn State. Credit: Jaydyn Isiminger / Penn State

This explains why the modern continental crust only began to form about 3 billion years ago.

Before that, Earth was too hot-the radioactive heat was twice what it is today.

Only when the planet “learned” to expel this fire did the continents gain the strength to last billions of years.

And it doesn’t stop there.

This same process that forged the continents also transported treasures: lithium, tin, tungsten, rare earths-essential metals for cell phones, electric cars, and solar panels.

Understanding how they rose in the past can help find them today.

Even more: the same “recipe” may be happening on other rocky planets.

If scientists see signs of crust being “forged” at 900 C on distant worlds, this could be a clue that a stable base for life exists there too.

In the end, continents are not just old rocks.

They are the result of slow, precise, and fiery cooking-a true act of cosmic forging that transformed a chaotic planet into a lasting home.

And now, for the first time, we know exactly how fire made Earth habitable.

Published in 10/30/2025 09h15

Portuguese version

Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.

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