An international team looks back 12 million years for clues about the formation of these vast areas where no life can survive A satellite image ... Today’s largest open ocean dead zone, located in the ...

Fresh water, which is essential for life, appeared on Earth roughly four billion years ago – 500 million years earlier ... Earth was completely covered by ocean four billion years ago.

In research led by the University of Exeter, scientists looked at two warm periods in Earth's past, about 50 million years ago ... zone life evolved in the last few million years, when ocean ...