Early Clues: Ophiolites

One of the best clues that hydrothermal vents might exist was right on land. People had known about them for thousands of years, though they didn’t realize what they were.

As early as 3,000 B.C., people mined copper from massive ore deposits on the island of Cyprus. It was the Roman Empire’s main source of the precious metal, which they originally called Cyprium. (Later it became “cuprium,” the root of the English word “copper.”)

In the early 1970s, scientists began to recognize that massive metal-rich ore deposits like the ones on Cyprus were actually within pieces of the seafloor that literally had been left high and dry. These slivers of seafloor, called ophiolites, were pieces of ancient mid-ocean ridges that had been thrust up onto continents by the movements and collisions of Earth’s tectonic plates. They are found in many places around the world.

Ophiolites became a convenient place to examine the results of chemical and geological processes that took place at and beneath ancient mid-ocean ridges. With new eyes, scientists closely investigated ophiolites. The mineral deposits in ophiolites pointed to the existence of seafloor hydrothermal vents.

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