Deep Earth movements may explain missing rock layers
· BehindLines newsroom
In some landscapes, relatively young rocks lie directly on much older formations. Between them, a long stretch of history is absent from the preserved layers. This interruption, known as the Great Unconformity, can be seen at the Grand Canyon. Depending on the location, it represents around 200 million to more than a billion years.
A study by Santosh Dhungana and Nicolas Flament, published in Nature on November 4, proposes connecting these gaps with movements in Earth’s mantle. The University of Wollongong presented it on November 5; Ars Technica subsequently examined it with one of the researchers.
Uplift, erosion, then burial
The scenario combines prolonged continental uplift during the Neoproterozoic with a lengthy period of subsidence. Raised terrain becomes exposed to erosion. Its later descent then allows seas and new sediments to cover it.
The mantle would not, however, have done all the erasing by itself. Glaciers play an essential role in the proposed erosion: uplift would be too gentle to remove enough rock alone. The combination of processes therefore matters as much as their sequence.
The authors compare their mantle-convection models with the distribution and volume of preserved sediments. They are not directly watching those ancient landscapes move. Instead, they test whether a scenario can reproduce features of today’s geological archive.
An explanation still to be tested
The 6 simulations do not produce identical results everywhere. Ancient continental positions and reconstructions of ocean floors remain uncertain, as Ars Technica’s account notes.
The study also considers environments preceding the Cambrian diversification of animal life. That connection opens a research avenue; it does not demonstrate that deep Earth movements alone triggered the diversification.
For readers, the interest lies in linking two scales: changes inside Earth can contribute to the conditions that erase and later preserve its surface record. The mystery is not declared definitively closed.