Final answer:
Geologists discovered magnetic stripes on the ocean floor, evidence of mid-ocean ridges and seafloor spreading, which supported the theory of continental drift and led to the theory of plate tectonics.
Step-by-step explanation:
One significant feature that geologists of the 1950s and 1960s discovered using electronic magnetometers and seismometers, which supported the theory of continental drift, was the pattern of magnetic stripes on the ocean floor. This pattern revealed that new crust was being formed at mid-ocean ridges, and that this new crust was symmetrically aligned with respect to the ridge on either side.
Furthermore, the finding that rocks equidistant from the ridge were magnetized in opposite directions provided compelling evidence of magnetic reversals and seafloor spreading. These discoveries were crucial in cementing the acceptance of plate tectonics, the theory that describes the large-scale movements of Earth's lithosphere. The mapping of the ocean floor and understanding of seafloor spreading eventually helped to clarify how and why continents move, expanding upon Alfred Wegener's initial theory of continental drift.