What Is a Hydrothermal Vent?

Hydrothermal vents and the marine communities they support

Marine Hydrothermal Vent
Marine hydrothermal vent underwater.


Marius Hepp/EyeEm/Getty Images

Despite their forbidding appearance, hydrothermal vents support a community of marine creatures. Here you can learn the definition of hydrothermal vents, what they're like as a habitat and what marine creatures live there. 

How Hydrothermal Vents Form

Hydrothermal vents are essentially underwater geysers created by tectonic plates. These huge plates in the Earth’s crust move and create cracks in the ocean floor. Ocean water enters the cracks, is heated up by the Earth’s magma, and then released through the hydrothermal vents, along with minerals such as hydrogen sulfide, which end up forming volcano-like projections on the seafloor.

The water coming out of the vents can reach incredible temperatures of up to 750 degrees F, even though the water outside of the vents can be near freezing in temperature. Although the water coming out of the vents is extremely hot, it isn't boiling because it is unable to under the high water pressure.

Due to their remote location in the deep sea, hydrothermal vents were discovered relatively recently. It wasn't until 1977 that scientists in the submersible Alvin were amazed to discover these undersea chimneys spewing hot water and minerals into the cold waters thousands of feet below the ocean surface. It was even more surprising to discover these inhospitable areas teeming with marine creatures.

What Lives in Them?

Living in a hydrothermal vent habitat presents challenges that prevent many marine creatures from inhabiting this hostile environment. Its inhabitants need to contend with total darkness, toxic chemicals, and extreme water pressure. But despite their intimidating description, hydrothermal vents support a wide variety of marine life, including fish, tubeworms, clams, mussels, crabs, and shrimp.

Hundreds of species of animals have been identified in the hydrothermal vent habitats around the world. At a hydrothermal vent, there is no sunlight to produce energy. Bacteria-like organisms called archaea have solved this problem by using a process called chemosynthesis to turn chemicals from the vents into energy. This energy-creating process drives the entire hydrothermal vent food chain. Animals in the hydrothermal vent community subsist on products produced by the archaea, or on the minerals in the water produced from the vents. 

Types of Hydrothermal Vents

Two types of hydrothermal vents are the "black smokers" and "white smokers."

The hottest of the vents, the "black smokers," got their name because they spew a dark "smoke" composed mostly of iron and sulfide. This combination forms iron monosulfide and gives the smoke its black color.

The "white smokers" release a cooler, lighter material composed of compounds including barium, calcium, and silicon.

Where Are They Found?

Hydrothermal vents are found at an average underwater depth of about 7,000 feet. They are found in both the Pacific and Atlantic Oceans and concentrated near the Mid-Ocean Ridge, which winds its way along the seafloor around the globe.

So What's the Big Deal?

Hydrothermal vents play an important part in ocean circulation and regulating the chemistry of ocean waters. They contribute nutrients required by ocean organisms. Microbes found at hydrothermal vents may also be important to the development of medicines and other products. Mining of minerals found at hydrothermal vents is an emerging issue that may allow scientists to learn more about hydrothermal vents, but may also damage the seafloor and surrounding marine communities.


  • Cowan, A.M.Deep Sea Hydrothermal Vents. National Geographic.
  • Pfeffer, W. 2003. Deep Oceans. Benchmark Books. 38pp.
  • Viders, H. 2011. Hydrothermal Vents. Alert Diver Online.
  • Woods Hole Oceanographic Institution. What Are Hydrothermal Vents?
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Kennedy, Jennifer. "What Is a Hydrothermal Vent?" ThoughtCo, Feb. 16, 2021, thoughtco.com/what-is-a-hydrothermal-vent-2291778. Kennedy, Jennifer. (2021, February 16). What Is a Hydrothermal Vent? Retrieved from https://www.thoughtco.com/what-is-a-hydrothermal-vent-2291778 Kennedy, Jennifer. "What Is a Hydrothermal Vent?" ThoughtCo. https://www.thoughtco.com/what-is-a-hydrothermal-vent-2291778 (accessed June 3, 2023).