US — Ars Technica

Earth's churning mantle may have created the Great Unconformity

SpaceNovember 7, 20261 min read

Scientists think a huge gap in Earth's rock record, called the Great Unconformity, may have been carved by slow, hot currents deep inside the planet. This idea challenges the older view that ice sheets did the job alone.

A missing chunk of time in the rock

In the Grand Canyon, a line in the rock marks a gap where a lot of time is missing. Old crystal-like rocks sit at the bottom, and younger sandstone sits on top. Researchers Nicolas Flament and Santosh Dhungana say that deep forces inside Earth helped carve this gap. Their study appeared in the journal Nature.

Key numbers

The gap can last from about 200 million years to more than 1 billion years.
The oldest rocks sitting on the gap in North America are 482 to 635 million years old.
Glaciers are about 10 times more effective than rivers at wearing away rock, according to Flament.
Glaciers reached the tropics between about 720 and 635 million years ago.

The old explanation: ice

The leading idea was that huge ice sheets scraped the land flat. Some scientists even думают that the whole planet froze, a idea called Snowball Earth. But if the whole planet had frozen, the gap would appear everywhere. It does not, so ice alone may not explain it.

Why it matters

The new idea says the planet's inside can move continents up and down over hundreds of millions of years. This means the rock record may show signs of deep Earth processes, not just surface weather. It helps scientists understand how the planet's surface has changed over time.

What to watch

More tests of the new models against rock evidence.
Studies of rock gaps in other places, such as northern Europe and northern China.
Further research on how slow hot rock currents move under continents.

Glossary

Great Unconformity: A gap in the rock record where a large amount of time is missing between old and young rock layers.
Snowball Earth: An idea that the whole planet was covered in ice for a long time, long ago.
Nature: A well-known science journal that publishes research studies.

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