An Entire Layer of Earth's History Could Have Been Ripped Away by Ice

The Earth’s crust is a visual timeline that goes back billions of years. But all over the world, there’s a gap in the timeline—a huge chunk of crust that should be there yet isn’t. Now, scientists say that the crust may have been destroyed during Snowball Earth, a hypothetical period in which the globe was covered in ice.

The gap in Earth’s timeline is known as the Great Unconformity, and represents 250 million to 1.2 billion years of lost time. The crust timeline abruptly jumps from the Cambrian Period, which saw the most intense burst of evolution, and the Precambrian time, during which the Earth was formed—meaning that it skips over about one-fifth of Earth’s geological history.

https://www.history.com/news/earth-crust-great-uncomformity-theory