Answer: subduction and sea floor spreading
Step-by-step explanation:
He knew that the continents today were once joined together by fossil records of plants and animals that were found to be on continents far removed from each other. He knew this also by corresponding land forms that matches up as well. What he couldn’t prove is how the land masses would have moved so far away from each other. Subduction and sea floor spreading move the tectonic plates that the continents sit on. That’s what he was missing.