sediments filled the ocean basins the sea levels gradually rose, and periodically there were events of rapid ocean bottom subsidence that increased the ocean's capacity and caused the regressions. Chamberlin proposed that instead of a thermal contraction, diastrophic movement was caused by gravitational contraction. In the United States, it was not until the late 1960s that thermal convection replaced the shrinking Earth theories. Notes Further reading Chorley, Richard J. (1963). "Diastrophic Background to Twentieth-Century Geomorphological Thought". Geological Society of America Bulletin 74(8): pp. 953–970. Structural geology Earth's crust