Earth may have been a 'waterworld' without continents 3 billion years ago, study suggests - USA TODAY

Earth may have been a 'waterworld' without continents 3 billion years ago, study suggests  USA TODAY

Earth may have been a 'waterworld' without continents 3 billion years ago, study suggests - USA TODAY
Earth may have been a 'waterworld' without continents 3 billion years ago, study suggests  USA TODAY