Around the world, miles of rock are missing. Could 'Snowball Earth' be the culprit?
When the famed explorer John Wesley Powell bumped, splashed and thrashed his way down the Colorado River in 1869, he discovered one of the most striking geologic features on Earth. Not the Grand Canyon although that too is a marvel but a conspicuous boundary between the sunset-colored sediments of the upper walls and the dark, jagged rocks below them.
Powell had learned to read the layers of desert rocks like pages in a book, and he recognized that the boundary represented a missing chapter in Earths geological history. Later, researchers realized it was more like an entire lost volume, spanning roughly one-fifth of Earths existence, and that a similar gap existed in many places around the world.
There must have been some sort of special event in Earths history that led to widespread erosion, said Steve Marshak, a geologist at the University of Illinois at Urbana-Champaign who studies what has come to be known as the Great Unconformity.
New research suggests it was something special indeed. Scientists propose that several freak episodes of global glaciation scoured away miles of continental crust, obliterating a billion years of geologic history in the process.
https://www.latimes.com/science/sciencenow/la-sci-sn-snowball-earth-geology-20190103-story.html