Around the globe our earth is missing miles of rock from a certain time in geological history and until recently this fact was a complete mystery. Now we have a possible explanation. The earth, for some reason, several times around 720 million years ago and again 580 million years ago became a huge snowball and massive glaciers scrubbed the surface, depositing mineral riches into the seas. The missing rock layers from this cataclysmic errosion can be observed as something called the great unconformity at the Grand Canyon.
As the ice melted over a thawing snowball earth, complex life exploded about 540 million years ago. Ninety percent of animal phyla that exist today appeared in a short 10 million year window of time known as the Cambrian Explosion.
The Earth is missing some of its crust, and now scientists have a new lead on what’s to blame: A lot of glaciers.
Nearly 720 million years ago, Earth was cloaked in global ice, an era known as Snowball Earth. The grinding of these worldwide ice sheets may have bulldozed between 1.8 and 3 miles (3 and 5 kilometers) of crust into the oceans, researchers reported Dec. 31. There, plate tectonics crunched it back into Earth’s hot middle layer, the mantle, recycling it into new rock. …
If the scientists are right, Snowball Earth explains a very weird feature of geology called the Great Unconformity. Seen around the world, this unconformity refers to a layer where sedimentary rocks have been deposited right on top of the oldest basement rock of the crust. Bizarrely, hundreds of millions of years of sedimentary layers are missing between this igneous or metamorphic basement and the oldest preserved sedimentary rocks. In the Grand Canyon, for example, a mind-boggling 1.2 billion years of rock are simply missing.
… A story was emerging: Massive amounts of crust, rather suddenly transferred to ocean subduction zones to be crunched back down into the mantle. But if all that crust moved into the ocean, someone probably should have noticed the erosion, Keller said.
“And indeed we have — in the Great Unconformity,” he said. …
Around 700 million years ago, they found, the Earth’s impact craters were wiped nearly clean. Only two huge craters, the Sudbury basin in Canada and the Vredefort crater in South Africa, predate Snowball Earth — and those craters were staggeringly enormous, originally measuring 93 miles (150 km) and 185 miles (300 km) across, respectively. They’ve been eroded to a fraction of their original size. …
… results suggest that the formation of the Great Unconformity may have triggered the Cambrian explosion.
“This feature explains a lot of lingering questions in different arenas, including the odd occurrences of many types of sedimentary rocks and a very remarkable style of fossil preservation. …
Read more at PhysOrg
One theory is that a random or even a periodic appearance of solar system disturbing space objects (planet X?) moved the earth’s orbit at times, causing major cooling changes.
I do not think the survival of our species long term is a given. The more we learn, the more the Earth’s history of periodic global cataclysms highlights the need to explore space and to establish earth outposts on other planets.
A strange truth is that we may all owe our existence to snowball earth glaciers giving the seas the ground up mixed minerals needed to support our version of life. Remember this the next time you see a snowman. ❄️ ⛄️👍