Mid-ocean ridges and plate tectonic theory
Step-by-step explanation:
The German geophysicist, Alfred Wegener, proposed the continental drift theory which explained about the drifting of continents from a single large mass.
With the advent of sonar-equipped ships, scientists were able to map the ocean floor. They collected topographic data from the ocean bed which showed them varied features like valleys, high mountains, flat plains etc.
Later, they discovered a ridge in the mid-Atlantic Ocean which ran parallel to the continental coastline and up above 1-2 km above the ocean floor. Then similar mid-ocean ridges were found in other major oceans like the Pacific and the Indian Ocean which also ran parallel to the continental coastline.
These ridges corresponded to hot magma regions which drifted the ocean floor corresponding with Wegner’s continental drift theory.
Later with the discovery of magnetometers and its usage in ships, scientists were able to detect the magnetism exhibited rocks on the sea floor.
Combining all the theories, the continental drift theory, ridges of mid-Atlantic Ocean, magnetism of rocks at ocean bed all led to the formulation of the plate tectonic theory.