GEOLOGY

Detailed explanation-1: -Harry Hess was a geologist and Navy submarine commander during World War II. Part of his mission had been to study the deepest parts of the ocean floor. In 1946 he had discovered that hundreds of flat-topped mountains, perhaps sunken islands, shape the Pacific floor.

Detailed explanation-2: -Hess’s bold intuition was subsequently corroborated. Later studies showed that the age of the ocean floor increases with distance from the ridge crests, and seismic studies confirmed that the oceanic crust was indeed sinking into the trenches.

Detailed explanation-3: -That enabled Hess to understand his ocean floor profiles in the Pacific. He realized that the Earth’s crust had been moving away on each side of oceanic ridges, down the Atlantic and Pacific oceans, that were long and volcanically active.

Detailed explanation-4: -Seafloor spreading was discovered by Harry Hess who used maps created by sonar readings of the ocean floor. He noticed long chains of underwater mountains with the rift valley at their centers (now known as mid-ocean ridges).

Detailed explanation-5: -About two thirds of the Earth’s surface lies beneath the oceans. Before the 19th century, the depths of the open ocean were largely a matter of speculation, and most people thought that the ocean floor was relatively flat and featureless.