Hydrothermal vent

Hydrothermal vents are special openings on the deep ocean floor where very hot water comes out. These openings are usually found where the Earth's plates are moving apart, like at mid-ocean ridges, or near places that are volcanically active. When the hot water from these vents mixes with the cold ocean water, it creates clouds of minerals that rise up into the water, forming what are called hydrothermal plumes.

Around these vents, there are many interesting creatures that have adapted to the extreme conditions. Unlike most plants and animals that need sunlight, the life around hydrothermal vents depends on special tiny organisms that can use chemicals from the vents to make food. These organisms form the base of a unique food chain that supports animals such as giant tube worms, clams, limpets, and shrimp.

Scientists think that hydrothermal vents might have played an important role in the very beginning of life on Earth. The conditions inside these vents could help create the basic building blocks needed for life. Some researchers believe that vents, especially those with certain types of water, are good places for these important molecules to form. However, how life first started is still a big mystery with many different ideas.

Physical properties

Hydrothermal vents in the deep ocean usually form along places where two tectonic plates are moving apart, such as the mid-ocean ridges like the East Pacific Rise and the Mid-Atlantic Ridge. The water from these vents is mostly seawater that gets pulled into the system near volcanoes, mixed with some water from deep inside the Earth.

This water comes out much hotter than the very cold ocean around it—sometimes as high as 464 °C! Because of the deep ocean’s pressure, the water can stay liquid even at these high temperatures, and in some places, it acts like a special kind of fluid that is neither gas nor liquid. Scientists are still learning what this means for the ocean and life there.

Black smokers and white smokers

Some hydrothermal vents create tall, tower-like structures made from minerals. These towers can grow up to 60 meters high. One famous tower named “Godzilla” stood 40 meters tall before it fell over.

Black smokers are special vents on the ocean floor that look like dark chimneys. They release hot water from deep inside the Earth, carrying minerals that form dark smoke. These vents were first found in 1979 and are now known in many parts of the ocean. They can be very deep, with some of the deepest found 5,000 meters below the surface.

White smokers are another type of vent that release lighter-colored minerals like barium, calcium, and silicon. They usually have lower temperature water because they are farther from the main heat source. Both black and white smokers can be found in the same area, but white smokers often appear later when the heat source moves away.

Hydrothermal plumes

Hydrothermal plumes are clouds of hot water that rise from places on the ocean floor where hot water bursts out. These places are called hydrothermal vents. The water from these vents is very hot and has different chemicals than the surrounding ocean water. As this hot water rises, it mixes with the colder ocean water, creating interesting chemical changes.

Scientists can find these vents by looking for special gases in the water. One gas, called helium-3, comes from deep inside the Earth and helps show where vents are. These plumes also carry important metals like iron and manganese, which can affect life in the ocean. Even though these metals can be good for some sea creatures, they can also take away other important nutrients from the water.

Biology of hydrothermal vents

Life usually relies on energy from the sun, but deep-sea creatures cannot use sunlight. Instead, communities around hydrothermal vents depend on nutrients in the chemical deposits and fluids around them. These areas have far more life than the surrounding sea floor.

Hydrothermal vents support life through a process called chemosynthesis. Here, special bacteria use chemicals like hydrogen sulfide, found in vent water, to create food. These bacteria are important because they feed many other sea creatures, creating rich ecosystems even without sunlight. The vents also add iron to the ocean, which helps tiny plants called phytoplankton grow.

Discovery and exploration

See also: Volcanogenic massive sulfide ore deposit

In 1949, a deep water survey found very hot water in the middle of the Red Sea. Later work in the 1960s showed the presence of hot, salty water and mud connected to an active area under the sea. This water was too salty for most living things to survive.

In June 1976, scientists found the first evidence of underwater hot water spots along the Galápagos Rift, a part of the East Pacific Rise, during the Pleiades II expedition. In 1977, the first scientific papers about these hot water spots were published. In 1979, very hot water spots called “black smokers” were discovered. These spots shoot out hot water and minerals from tall chimneys. Scientists have been studying these areas ever since to learn more about the ocean and Earth.

Distribution

Hydrothermal vents are found along the edges where Earth's plates move, but they can also appear in special spots called hotspot volcanoes. As of 2009, scientists knew of about 500 places where these vents are active under the sea. Some of these places were seen directly, while others were found by looking at clues in the water or on the ocean floor.

Rogers and others, in 2012, identified at least 11 different areas where these vents are found:

1. Mid-Atlantic Ridge province,
2. East Scotia Ridge province,
3. northern East Pacific Rise province,
4. central East Pacific Rise province,
5. southern East Pacific Rise province,
6. south of the Easter Microplate,
7. Indian Ocean province,
8. four provinces in the western Pacific and many more.

Exploitation

Hydrothermal vents can create areas rich in important minerals like cobalt, gold, copper, and rare earth metals. These minerals are very useful for making electronic devices. Recently, companies have started looking at ways to collect these minerals from the ocean floor.

Some countries, like Japan, are especially interested in getting these minerals from the sea because they need to import most of their minerals. Scientists and companies are working to understand how to mine these areas safely and carefully, as there are concerns about how this might affect sea life and the environment.

Conservation

People have talked a lot about how to protect hydrothermal vents for the past 20 years. Sometimes, scientists who study these vents might accidentally damage them. There are rules about how scientists should behave, but there is no worldwide law to protect these special places.

One big concern is taking minerals from the deep sea, called deep sea mining. Four main minerals are being looked at for this: manganese nodules, cobalt-rich crusts, seafloor massive sulfides, and phosphorite nodules. Seafloor massive sulfides are found near hydrothermal vents and contain important minerals like iron sulfides. However, we do not know much about how taking these minerals will affect the vents. Studies of vents after volcanic activity show it can take 3–5 years for tiny life to return and about 10 years for larger animals. The types of animals might also change, which could affect special species that live only in these harsh environments. More research is needed to understand these impacts better. Scientists are also worried about how climate change, like ocean acidification and rising temperatures, might affect these vents and the animals that live there.

Geochronological dating

Scientists use special ways to find out how old hydrothermal vents are. They look at minerals like sulfide and sulphate, such as pyrite and baryte. Two common ways to find the age are radiometric dating and electron spin resonance dating. Each method has its own challenges, like needing very pure minerals or dealing with heating that can change the age. Sometimes, different methods give different ages for the same sample because they focus on different parts of the mineral's history.

History and formation of hydrothermal vents

Further information: Alternative abiogenesis scenarios § Deep sea alkaline vents

Hydrothermal vents are places in the deep sea where hot water flows out from the Earth’s crust. Scientists have found many of these vents, but we still don’t know where all of them are because most of the ocean floor has not been explored. Many vents are found where the Earth’s tectonic plates move apart, called mid-ocean ridges.

Long ago, during a time called the Paleocene and Eocene, movements in the Earth’s crust caused gases, liquids, and sediments to burst out. This created large craters on the seafloor. Over time, these craters became home to hydrothermal vents. These vents have special features like layers of rock that dip inward and tall structures called chimneys. The hot water from these vents changes the chemistry of the surrounding area, creating a rich environment where unique tiny living things can survive.