Snowball Earth

Snowball Earth melting led to freshwater ocean 2 kilometres deep

A little more than 600 million years ago, you could have drunk from the ocean.

After an extreme ice age known as snowball Earth, in which glaciers extended to the tropics and ice up to a kilometre thick covered the oceans, the melt formed a thick freshwater layer that floated on the super-salty oceans. Read more in New Scientist.