“In 1960, American geophysicist Harry H. Hess proposed the seafloor spreading theory using evidence from Marie Tharp's seafloor maps.”

The article states that Tharp's work provided evidence and weight to the theory of plate tectonics, and that her work was really about seafloor spreading, which occurs at the mid-ocean ridges that she was the first to map.

The U.S. Geological Survey states that Hess’s ideas were published in 1962 in a paper titled "History of Ocean Basins," which was one of the most important contributions to the development of plate tectonics. The same USGS page identifies Harry Hammond Hess as the geologist associated with spreading the seafloor.

The article says that in 1962 Harry Hess formally proposed seafloor spreading, and that Tharp's pioneering mapping in the 1950s was a major reason the old assumption about the ocean floor began to crumble. It also notes that Tharp hypothesized new crust formed at sites like the Mid-Atlantic Ridge.

Britannica says the seafloor spreading hypothesis was proposed by Harry H. Hess in 1960. It adds that the first comprehensive explanation was a widely circulated manuscript written in 1960 but not formally published for several years.

The article says Tharp's maps helped scientists reconsider seafloor geology, and that her observations from the late 1950s through the 1970s helped establish the existence of a massive underwater ridge with a crack down the middle. It calls her one of the unsung heroes of the seafloor spreading-plate tectonics revolution.

Britannica states that the seafloor spreading hypothesis was proposed by the American geophysicist Harry H. Hess in 1960. It further says that, on the basis of Tharp’s efforts and other new discoveries about the deep-ocean floor, Hess postulated mantle material upwelling along mid-ocean ridges.

Hess’s seafloor spreading model was supported by several lines of evidence: at or near the crest of the ridge, the rocks are very young, and they become progressively older away from the ridge crest; the youngest rocks at the ridge crest always have present-day normal polarity; and stripes of rock parallel to the ridge crest alternated in magnetic polarity. When the ages of the samples were determined by paleontologic and isotopic dating studies, they provided the clinching evidence that proved the seafloor spreading hypothesis.

The article states that Tharp's map of the valley and its alignment with earthquake data helped provide a basis for the theory of seafloor spreading. It says this theory explained how continents could be pushed farther apart by new oceanic crust and that the idea was eventually accepted as critical to plate tectonics.

PBS says that after much thought, Hess proposed in 1960 that the movement of the continents was a result of sea-floor spreading. Another PBS page says that in 1960, and with further elaboration in 1962, he hypothesized that the sea floor was spreading from vents in the rift where hot magma oozed up.

The article says that the discovery of the Mid-Atlantic Ridge was a revelation, but nobody could explain how it got there. It also states that Princeton's Harry Hess later published his theory of seafloor spreading in his 1962 History of Ocean Basins, inspired after hearing a 1957 talk by Heezen about the 'Great Global Rift.'

A Smithsonian American Museum of Natural History page says that in 1962 Hess proposed a groundbreaking hypothesis and that his report, History of Ocean Basins, was formally published in 1962. It describes the later-named seafloor spreading process as new seafloor created at mid-ocean ridges and recycled at trenches.

The article says that Tharp's groundbreaking maps helped tilt scientific opinion toward acceptance of continental drift and clear a path for the emerging theory of plate tectonics.

In the 1960s Bruce Heezen and Marie Tharp published the first detailed seafloor maps, arguing that mid-ocean ridges are not just fissures in Earth's crust, but also active spreading zones where new oceanic crust forms. In 1964 Vine and Matthews published the discovery of parallel stripes of magnetized igneous rocks along the ocean floor, and Canadian geologist Lawrence W. Morley independently realized the significance of the magnetic pattern as direct evidence of seafloor spreading.

The Library and Archives of the Geological Society of London says Hess published The History of Ocean Basins in 1962 and outlined a theory that could explain how the continents could actually drift. It says this theory later became known as sea floor spreading.

The article states that Tharp's discovery of the 10,000-mile-long Mid-Atlantic Ridge showed that the seafloor was spreading, and that her maps are now seen as evidence for seafloor spreading and continental drift. It also says Heezen initially dismissed her interpretation as 'girl talk.'

The article says Tharp's maps in the 1950s would spark debate and later the discovery of the Mid-Atlantic Ridge, one of the key clues supporting continental drift. It adds that with Tharp's ocean floor maps in hand, scientists in the 1960s formulated plate tectonics.

The article says Tharp's work revealed a continuous rift valley along the Mid-Atlantic Ridge axis, which led to acceptance of plate tectonics and continental drift. It also says that by piecing maps together in the late 1940s and early 1950s, Marie Tharp and Bruce Heezen concluded that the seafloor spreads from mid-ocean ridges.

Linda Hall Library says that in 1960 Hess proposed a novel idea: magma from the Earth's mantle wells up along the mid-Atlantic ridge, forms new rock, and pushes the ocean floor apart. It also states that Hess announced the discovery in 1960 and published the results in 1962 in his chapter titled History of Ocean Basins.

The article says that underwater earthquake epicenters aligned with the rift valley on Tharp's diagrams, supporting theories of continental drift and plate tectonics. It describes this alignment as a discovery that helped validate the new tectonic ideas.

EBSCO’s research starter says Hess’s "History of the Ocean Basins" was published in 1962 but widely circulated beginning in 1960, and that in his 1960 report to the Office of Naval Research he proposed seafloor spreading as the mechanism for continental drift. It also notes that his theory drew on the newly available deep-ocean mapping data.

In 1960, Harry Hess, in the words of Robert Fisher, 'put it all together.' What Hess put together was a mass of seemingly unrelated data when he proposed his seafloor spreading hypothesis.

Harry Hess advanced the theory, now generally accepted, that the Earth's crust moved laterally away from long, volcanically active oceanic ridges. He only understood his ocean floor profiles across the North Pacific Ocean after Marie Tharp and Bruce Heezen discovered the Great Global Rift, running along the Mid-Atlantic Ridge.

The seafloor spreading hypothesis was supported by several lines of evidence, including that at or near the crest of the ridge, the rocks are very young and become progressively older away from the ridge crest. The youngest rocks at the ridge crest always have present-day normal polarity, and stripes of rock parallel to the ridge crest alternated in magnetic polarity.

A University of Hawaii geology resource says the idea was first hypothesized by Harry Hess in 1960, in a paper Hess later identified as 1962, and that it offered a simple explanation for the prevailing view that the Earth was mostly static and continents fixed. This is secondary educational material rather than a primary source.

The page states that Harry Hess formally proposed seafloor spreading in 1962 and that Tharp's maps and earlier observations were important evidence pointing toward that theory. It is a secondary educational source summarizing how Tharp's mapping and later Hess's theory fit together.

A University of Victoria geology handout says that in 1960 Harold Hess advanced a theory that had many of the elements now accepted as plate tectonics, and that until 1962 he did not even put his ideas in writing except internally to the Navy, presenting them mostly in lectures and seminars. It also says he proposed new seafloor was generated at ridges and old seafloor was dragged down at trenches.