When Alfred Wegener proposed the continental drift theory in 1912, many scientists criticized it.He couldn’t explain the mechanism of how continents moved.He suggested that continents “plowed” through ocean crust, which didn’t match known physics.No clear evidence then existed of sea-floor spreading or plate tectonics to support his idea.Only in the 1960s, when plate tectonics was discovered through studies of ocean floors and seismic data, did scientists accept the idea and validate Wegener's theory.