Do Vents Affect the Entire Ocean?
The world’s oceans contain many chemicals other than water and salt. Where do these chemicals come from? Rivers carry some of the chemicals into the ocean. Hydrothermal vents supply others. When seawater seeps down into the ocean crust and is heated by the magma, it undergoes lots of chemical reactions.

When the fluid rises up through the seafloor, it carries many new chemicals with it, such as copper and zinc. These chemical reactions also remove chemicals from the seawater, such as oxygen and magnesium. Here is a look at some of the many chemical reactions that take place.

1. Cold seawater sinks down through cracks in the crust.

2. Oxygen and potassium are removed from the seawater.

3. Calcium, sulfate, and magnesium are removed from the fluid.

4. Sodium, calcium, and potassium from the surrounding crust enter the fluid.

5. The fluids have reached their highest temperatures. Copper, zinc, iron, and sulfur from the crust dissolve in the fluids.

6. Hot fluids carrying dissolved metals rise up through crust.

7. The hydrothermal fluids mix with cold, oxygen-rich seawater. Metals and sulfur combine to form black metal-sulfide minerals.

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Vents Around the World

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More than 200 hydrothermal vent fields have been observed so far, and there may be a thousand more remaining to be discovered, mainly along Earth’s plate boundaries.

Hot or molten rock (magma) beneath the ocean floor is the engine that drives hydrothermal vents. It heats the hydrothermal fluids, causing them to move upwards through the crust. Therefore, hydrothermal vents are found only in areas where there is volcanic activity and the magma is close enough to the surface to heat the fluids. Most of the vents scientists have discovered are along the Mid-Ocean Ridge. There are vents on the Loihi Seamount, the newest underwater volcano in the Hawaii chain. Vents are also found along some subduction zones.

Vents can occur at any depth. Some are as deep as 3,600 meters. Others off the coast of New Zealand are only 30 meters deep. Vents are also found on land. Two of the most famous examples are the hot springs and geysers in Yellowstone National Park in the United States and on the North Island of New Zealand.

Map data sources: InterRidge Vents Database; ETOPO1, NOAA NGDC; University of Texas PLATES Project; Credits: Stace Beaulieu, Michael Lowe, Erin LaBrecque, and Katherine Joyce (WHOI); Funding: NSF GEO#1202977