Hydrothermal vents are hot springs located on the ocean floor. The vents spew out water heated by magma, molten rock from below the earth's crust. Water temperatures of higher than 660°F. have been recorded at some vents.

Water flowing from vents contains minerals such as iron, copper, and zinc. The minerals fall like rain and settle on the ocean floor. Over time, the mineral deposits build up and form a chimney around the vent.

The first hydrothermal vents were discovered in 1977 by scientists aboard the submersible Alvin. The scientists found the vents near the Galápagos Islands in the eastern Pacific Ocean. Other vents were discovered in the Pacific, Atlantic, and Indian oceans.

In 2000, scientists discovered a field of hydrothermal vents in the Atlantic Ocean. The area called the "Lost City" contained 180-feet tall chimneys. These were the largest known chimneys.

Hydrothermal vents are located at ocean depths of 8,200 to 10,000 feet. The area near a hydrothermal vent is home to unique animals. They exist without sunlight and live in mineral-levels that would poison animals living on land. These unique animals include 10-foot-long tube worms, 1-foot-long clams, and shrimp.