Figure: Photographed on Kangaroo Island, this rock – called a ‘zebra schist’ – deformed from flat-lying marine sediments through being stressed by a continental collision over 500 million years ago. Dietmar Muller CC BY Dietmar Müller, University of Sydney ; Maria Seton, University of Sydney , and Sabin Zahirovic, University of Sydney Classical plate tectonic theory was developed in the 1960s.