While other scientists like Alfred Wegener had proposed continental drift, Hess's theory of seafloor spreading in the 1960s provided a mechanism for how continents could move. He proposed that new oceanic crust was being created at mid-ocean ridges and then spread outwards, pushing the continents apart.

Hess's theory was later supported by evidence such as:

* Magnetic stripes on the ocean floor: These stripes, alternating in polarity, provided evidence of seafloor spreading and the creation of new oceanic crust.

* Age of ocean floor: The ocean floor is much younger than the continents, supporting the idea of continuous creation and destruction of oceanic crust.

* Earthquakes and volcanoes: These are concentrated along mid-ocean ridges and subduction zones, which are consistent with the theory of seafloor spreading.

Hess's work was crucial in the development of the theory of plate tectonics, which revolutionized our understanding of Earth's geology and dynamics.