Ocean Matters

Marine Hydrothermal Vents

The History of Deep Sea Exploration

Up until about 125 years ago, the deep ocean floor was a mystery to most people. Scientists knew very little about the ocean depths except that there were many different species and a lot of water. The first major ocean exploration was from the Challenger Expedition from 1872-1876. The Challenger expedition covered seventy thousand nautical miles of ocean and the researchers took depth soundings every one hundred miles. Scientists regarded these depth recordings as accurate (they weren't) but it was not for many years until there was a better depth recording method.

Beginnings of Ocean Exploration

The Titanic disaster of 1912 prompted the development of a new system for distance and depth recording. This new development was called the Echo Sounder. The sounder bounced waves off the ocean floor and when they returned to the ship the operator was able to discern how deep the ocean was. This new system was problematic because the returning sound waves were difficult to hear. It was sort of like trying to listen to a radio station with a lot of static interference. The development of this sounder continued and by the 1930's it could get reasonably accurate depth recordings because the British developed a series of tables that provided a depth based on the level of returning sound. Throughout the 1950's and beyond, depth recording mechanisms improved and scientists were able to make accurate maps of the seafloor, forever changing how people thought of the ocean floor. The figure below provides a simple explanation of how the Echo Sounder works.

The discovery of oceanic ridges changed our perception of the ocean. These various oceanic ridges were incredibly long (up to thirty-three thousand miles) and rose to heights of fifteen thousand feet in some places. At the center of the oceanic ridges molten magma was rising up, thus creating oceanic plates. These oceanic ridges confirmed earlier theories that the Earth was composed of tectonic plates sliding over the Earth's mantle. Many scientists believed that it was possible to find Hot Springs at these ridges from superheated water rising up to the surface.

This image shows the world distribution of the marine oceanic ridges. The ridges themselves are demarcated by the whitish lines in the oceans. All Images used with permission from the New Millennium Observatory

This image shows a spreading oceanic seafloor. As the two oceanic plates separate, magma rises up to the surface. Given enough time this process can create mountains like the Mid-Atlantic ridge and the Juan de Fuca Ridge.

This diagram is of the hydrothermal circulation in a mid-oceanic ridge.

Discovery of Marine Hydrothermal Vents
Into the 1970's, researchers explored the Mid-Atlantic ridge looking for potential hot springs but did not find any. In 1977, however, the scientific community made an astounding discovery by finding marine hot springs at the Galapagos Rift. These hot springs were unlike anything previously discovered on Earth.

When scientists were first able to see what lay around the hot springs, they were astonished. There were new species of tube-worms that had never been seen before along with other species that were completely different from anything known to science. The hot springs (also known as black smokers) were up to 45 feet tall, with water spewing from them up to 600 degrees Fahrenheit. There were clouds of bacterial clumps in the water and on the ocean floor that gave the landscape an unusual beauty. One of the scientists that helped make the discovery, Alexander Malahoff, stated that the density of life found at the hot springs exceeded that of any land-based system. The following two figures illustrate what was found at the hot vents.

These two images show a Black Smoker spewing out water and hydrogen sulfides and some tube worms that live nearby. No scientist had ever observed this tube worm species until their discovery near hydrothermal vents.

The fact that life was able to exist and thrive at such deep ocean depths was a mystery to scientists. Furthermore, deep sea vents contain massive amounts of hydrogen sulfide, which is normally toxic to life. Eventually scientists found out that bacteria living on and around the deep sea vents were “fixing” or converting hydrogen sulfide into usable energy. Scientists also determined that the very same bacteria were actually the basis of deep sea vent food chains, much like plants provide the bottom of the food chain in land-based ecosystems. All of the other life forms in the hot vent such as the tube-worms, clams and mussels were dependent on the bacteria for their food. Without the bacteria fixing energy, life would not be possible at the hot vents.

 From left to right these animals are: a Pandorae Worm, Sea Spider, Sulphide Copepod and a Vent Clam. These species are only found at hydrothermal vents.

The discovery of marine hot vents was one of the most important ocean discoveries in the 20th century. Today, researchers continue to make exciting findings at deep sea hydrothermal vents, with new species being described all the time.

This map shows the area where research is currently being conducted near the Juan de Fuca ridge.

For more information go to:
Dive and Discover
Vancouver Aquarium: The Endeavour Hydrothermal Vents
Victoria Experimental Network Under the Sea (VENUS)
World Wildlife Fund: Deep Sea Ecology
New Millennium Observatory, and check out the videos!

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