The theory of seafloor spreading was discovered and first proposed by the American geologist Harry Hess in the early 1960s.

Quick Scoop

  • Harry Hess developed the idea while analyzing sonar maps of the ocean floor collected during and after World War II.
  • In a 1962 paper titled History of Ocean Basins , he proposed that new oceanic crust is created at mid‑ocean ridges and spreads outward, a process later named seafloor spreading.
  • This concept became a key piece of evidence for plate tectonics, explaining how continents move over geological time.

A tiny bit of story

Hess had served in the U.S. Navy, where ships used sonar to detect submarines and, as a by‑product, mapped the shape of the seafloor.

He noticed long underwater mountain chains (mid‑ocean ridges) and suggested that molten rock wells up there, forming new crust that slowly pushes older crust away and helps drive continental drift.

TL;DR: Harry Hess is credited with discovering and formulating the theory of seafloor spreading, which underpins modern plate tectonics.

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