Not only is water everywhere, but it has can have a massive effect on surfaces. As said in the Doctor Who episode “The Waters of Mars”, “Water always wins.” And it turns out, it can win in a big way.

One of the last remaining major mysteries of geology here on Earth is a gap in the rock record that covers hundreds of millions to billions of years and is seen across much of North America, including most notably the Grand Canyon. An unconformity is a place in the rock record where rocks of very different types rest on one another, particularly sedimentary rocks on other types, and they imply that some sort of massive change in the environment occurred.

In the case of the Grand Canyon and the Great Unconformity, sedimentary rocks are missing from between the basement rocks and volcanic and metamorphic rocks that date to about 1.2 to 1.6 billion years later. In some places, the missing rock only totals about 725 million years. And in new research published in the Proceedings of the National Academy of Sciences, scientists have determined that the missing sedimentary rocks were eroded by the melting and pulling back of three-to-five-kilometer-thick glaciers from the Cyrogeian snowball Earth period.

So Earth forms, gets bombarded; water rises from the core, water freezes, water melts, sedimentary rocks get eroded, and basement rock gets revealed. There you have it. History is much bigger than just the last few hundred years or so, isn’t it?

More Information

Dartmouth press release

“Thermochronologic constraints on the origin of the Great Unconformity,” Kalin T. McDannell et al., 2022 February 1, PNAS