Final answer:
Hess proved sea floor spreading using sonar technology, which is integral for mapping the ocean floor and identifying mid-ocean ridges where sea floor generation occurs.
Step-by-step explanation:
Hess was able to prove that the sea floor was spreading through the use of sonar technology. Sonar, which stands for Sound Navigation and Ranging, is a technique that uses sound propagation to navigate, communicate, or detect objects under the surface of the water, such as the seabed. This advancement was instrumental in mapping the ocean floor and identifying the mid-ocean ridges where new sea floor is generated, thereby supporting the theory of sea floor spreading.