Terrawatch: snowball Earth – when glaciers reached the tropics

Rock deposits show there have been many times when the planet has been covered in ice

Once upon a time, about 650m years ago, our planet was covered in ice. Glaciers stretched as far as the tropics, and equatorial regions were as cold as modern day Antarctica.

Life clung on, huddling around geothermal springs and in pockets of liquid water under the ice caps. Ancient rock deposits suggest our planet entered this snowball state multiple times.