Movement of the old ocean floor - 500 million years ago. The west coast of Newfoundland was the continental margin of the Iapetus Ocean. Movement of the old ocean floor - Present. When Iapetus closed, giant slabs of the old ocean floor (ophiolite) and slope deposits were transported westward across the old continental margin. From A. B. Ryan, Newfoundland Journal of Geological Education, Vol. 7, No. 2, 1983. Adapted by Duleepa Wijayawardhana.