Interesting #geology read: There’s a break in the rock layers in many places worldwide, ending 700 million years ago. One hypothesis: an ice age with enough glacial activity to scour the crust worldwide. As it turns out, they’ve found signs of a massive surge in rocks being recycled through volcanoes around that time…
https://www.latimes.com/science/sciencenow/la-sci-sn-snowball-earth-geology-20190103-story.html