Seafloor spreading is a process that occurs at mid-ocean ridge

Mid-ocean ridge

A mid-ocean ridge is a general term for an underwater mountain system that consists of various mountain ranges , typically having a valley known as a rift running along its spine, formed by plate tectonics. This type of oceanic ridge is characteristic of what is known as an oceanic spreading...

s, where new oceanic crust

Oceanic crust

Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...

 is formed through volcanic activity

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift

Continental drift

Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...

 in the theory of plate tectonics

Plate tectonics

Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

.

Earlier theories (e.g. by Alfred Wegener

Alfred Wegener

Alfred Lothar Wegener was a German scientist, geophysicist, and meteorologist.He is most notable for his theory of continental drift , proposed in 1912, which hypothesized that the continents were slowly drifting around the Earth...

 and Alexander du Toit

Alexander Du Toit

Alexander Logie du Toit was a geologist from South Africa, and an early supporter of Alfred Wegener's theory of continental drift.Born in Newlands, Cape Town in 1878, du Toit was educated at the Diocesan College in Rondebosch and the University of the Cape of Good Hope...

) of continental drift were that continent

Continent

A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...

s "plowed" through the sea. The idea that the seafloor itself moves (and carries the continents with it) as it expands from a central axis was proposed by Harry Hess

Harry Hammond Hess

Harry Hammond Hess was a geologist and United States Navy officer in World War II.Considered one of the "founding fathers" of the unifying theory of plate tectonics, Rear Admiral Harry Hammond Hess was born on May 24, 1906 in New York City...

 from Princeton University

Princeton University

Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....

 in the 1960s.