Geologists solve 150-year mystery of Earth's missing billion-year rock layer
Deep Earth processes lifted ancient continents, then massive ice sheets scoured away rocks spanning up to a billion years of history.
The Great Unconformity is a gap in Earth's rock record where hundreds of millions of years of geological time vanishes. Rocks from two different ages sit directly atop each other with no layers between them.
New research explains how it happened. Hot mantle rock deep inside Earth rose and fell over hundreds of millions of years, lifting some ancient continents high above sea level.
Around a billion years ago, enormous ice sheets from Snowball Earth ground across their surfaces, scraping away all rock layers. Ice sheets worked like giant sandpaper, eroding continents far more effectively than rivers could.
This erased perhaps a quarter of Earth's history. The process altered seawater chemistry and may have set the stage for the Cambrian explosion, when complex animal life first flourished.
- 150 years
- Years of mystery
- Up to a quarter
- Earth's history erased
- Up to two billion years old
- Age of basement rock
- 720 to 635 million years ago
- Snowball Earth period
Why it mattersUnderstanding what shaped Earth's surface in deep time reveals how planetary processes created conditions for life itself to flourish.
AustraliaAustralian researchers used the Gadi supercomputer to solve this mystery, showing how mantle convection affected the continents that make up modern Australia.
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