Hydrothermal vents

What are Hydrothermal Vents?

In 1977, scientists exploring an oceanic spreading ridge near the Galápagos Islands made a stunning discovery: openings in the Pacific Ocean seafloor with warm, chemical-rich fluids flowing out. The discovery of these hydrothermal vents fundamentally changed our understanding of life on Earth.

Hydrothermal vents on the ocean floor are similar to hot springs found on land. Both form where magma under Earth’s crust heats subterranean water to extreme temperatures. That water erupts through the crust, sometimes forcefully, other times in gentle seeps.

In the ocean, most hydrothermal vents occur along mid-ocean ridges—long mountain chains that form where tectonic plates separate, allowing magma to bubble up toward the ocean floor. Cold water sinks into the seafloor through cracks in the rock. Once beneath the surface, underlying magma chambers heat the seawater, which causes it to chemically react with the surrounding rock.

These chemical changes transform seawater into hydrothermal fluid, which flows upward through hydrothermal vents, bringing a hot, chemical-rich flow into the ocean. The fluid venting out of the seafloor can reach temperatures of 400° Celsius (750° Fahrenheit). Minerals and chemicals provide a source of energy for deep-sea ecosystems that exist nowhere else on the planet.

Scientists recognize several types of hydrothermal vents, including two well-known types: black smokers and Lost City vents. Black smokers are tall, chimney-like structures that vent high-temperature mineral-rich fluids. As these fluids mix with cold seawater, iron sulfides and other minerals precipitate, creating the characteristic black “smoke.” Black smoker hydrothermal fluid typically measures around 350° Celsius (660° Fahrenheit) as it exits the chimney. Lost City vents are much cooler, releasing water between 50° and 90° Celsius (122° to 194° Fahrenheit).