About Hydrothermal Vents:
What are hydrothermal vents?
Hot springs on the ocean floor are called hydrothermal vents. The heat source for these springs is the magma (molten rock) beneath submarine volcanoes. Circulating seawater deep in the ocean crust gets very hot because of the high pressure and can dissolve many chemicals from the rocks. When the hot fluids exit the seafloor and mix with cold seawater, the dissolved chemicals precipitate instantly into tiny mineral particles, forming the plumes that we see at black smokers. Another form of hydrothermal venting is diffuse venting, where lower temperature fluids come out as shimmering water which generally do not contain enough dissolved metal and sulfide to form "smoke", but may support dense communities of vent animals.
Why are vents important?
Hydrothermal vents affect the chemistry and circulation in the oceans, and support unique deep-ocean ecosystems including chemosynthetic animals and thermophile or hyperthermophile microbes that live at or beneath the seafloor and are released into the ocean in hydrothermal plumes. Some of the species found at hydrothermal vents are some of the most primitive known and many scientist think that life on Earth many have begun at deep-ocean hot springs. The properties of hydrothermal microbes are useful for biotechnical applications. Also, hydrothermal venting at submarine volcanoes creates natural laboratories for studying the effects of ocean acidification on marine biological communities.
Plate tectonics and volcanic activity in the oceans
Mid-ocean ridges are where tectonic plates spread apart, creating new ocean floor and literally renewing the surface of our planet. Older crust is recycled back into the mantle elsewhere on the globe, typically where plates collide at subduction zones. The mid-ocean ridge consists of thousands of individual volcanoes or volcanic ridge segments which periodically erupt. Chains active volcanoes exist as seamounts above subduction zones.
What are “megaplumes”?
In 1986, a large plume of hot, particle laden water approximately one million cubic meters in volume was discovered over the North Cleft segment of the Juan de Fuca Ridge. This plume was unique in its shape (horizontally and vertically symmetric), size (100 km3) and rise height (~1km), indicating that an enormous volume of hot water had been released in a relatively short period of time. Later it was discovered this giant plume was associated with a volcanic eruption on the seafloor. Since then megaplumes (or “event plumes”) have been discovered at many other undersea eruption sites.
How are vents and eruptions located?
We never see most of the earth's volcanic eruptions, because most of them occur undetected in the deep ocean. An estimated 75% of the average annual volume of magma reaching the earth's surface is emplaced in the oceans. Two key methods for finding hydrothermal vents and submarine volcanic eruptions are water column surveys to look for hydrothermal plumes and hydrophone arrays to detect the sounds of earthquakes and volcanic eruptions.
How do we study vents on the seafloor?
The tools we use to study hydrothermal vents include: CTDs, camera systems, submersibles, remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs) and gliders, high-temperature water samplers, portable and moored hydrophones, and various monitoring instruments.