what are the similarities and differences of among the theories of continental drift, sea-floor spreading and?

Answer 1

The theory of Sea-floor Spreading and Plate Tectonics arose from the theory of Continental Drift. Although Continental Drift has some good evidence behind it, there was no mechanism to explain it. Sea-floor Spreading and Plate Tectonics provided that mechanism: Mantle Circulation. To be fair to the proponents of Continental Drift, features on the ocean floor were unknown to them in the early 1900's. Mid-oceanic rifts and deep trenches were not revealed till sonar and other deep-sea devices were developed.