Question

how has the theory of plate tectonics changed since it was originally proposed? how did that make it difficult for the theory to be accepted?

Explanation:

The theory of plate tectonics has evolved with new data from ocean - floor mapping, paleomagnetism studies, and seismic activity analysis. Initially, lack of a clear mechanism for plate movement and resistance from the scientific community used to established ideas made acceptance difficult.

Answer:

The theory has changed with new data from multiple sources. Difficulty in acceptance came from lack of a clear mechanism and resistance to new ideas.