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Deep sea vents bring new areas of exploration

WHITE SMOKERS are shown at the Champagne Vent.

WHITE SMOKERS are shown at the Champagne Vent. Wikimeda Commons

The discovery of hydrothermal deep sea vents in the late 1970s opened up multiple new areas of research and learning for geologists, chemists and biologists.

That superheated geysers existed deep under the ocean had been hypothesized earlier, so confirmation was undoubtedly exciting but not unexpected. The surprise was they were surrounded by thriving communities of life in one of the most extreme and inhospitable locations on Earth.

Deep sea vents were first discovered near the Galapagos Islands, famous for their finches that helped Charles Darwin recognize natural selection as a key part of evolution. Many more vents have since been found around the world; most occur along the Mid-Ocean Ridge system, a 40,000 mile string of geologic activity where the earth’s tectonic plates intersect.

Because of the enormous stresses on the earth’s crust in these areas, tiny cracks and fissures abound. Sea water under extreme pressure percolates through the cracks into the earth’s crust, dissolving minerals from the rock along the way. The water heats up as it travels deeper and closer to underlying molten rock, allowing it to carry increasing amounts of dissolved minerals. Higher temperatures also increase the water’s buoyancy, ultimately forcing it back up to the ocean floor through larger passages in the crust.

These underwater geysers average 7,000 feet in depth, where no sunlight penetrates, temperatures hover near freezing and pressures measure over 3,000 pounds per square inch. Such extreme conditions help explain some of the startling features of deep sea vents.

High surrounding pressures keep the venting water from boiling, despite temperatures up to 750 degrees. As the superheated water meets cold sea water, the dissolved minerals nearly instantly precipitate out, forming a cloud of particles resembling smoke. These minerals both enrich the surrounding ocean and pile up around the vent to form tall colorful chimneys. One vent chimney off the Oregon coast grew 15 stories tall before tumbling down and starting to rebuild.

Although deep oceans are the largest environment on earth, most sea life is found either in the intertidal zones along the coasts or near the surface, where food and sunlight are plentiful. The deep ocean bottom is sparsely populated, mostly covered by mud, ooze (mud high in organic material) or rock. Deep sea vents are the exception, like small isolated islands of heat and energy rich with life. This makes them ideal settings for evolution and the discovery of new species.

Indeed, many vent species have never been seen before, and often are unique to specific vents. New types of giant tubeworms, crabs, shrimp, clams and other life thrive around the water bursting from the rock below.

They do share some unusual traits. Protein and cellular adaptations allow vent life to survive at temperatures over 150℉ and pressures fatal to other species. Most surprising though is the primary source of energy for life around hydrothermal vents.

Nearly all life we know depends on photosynthesis. Plants, algae and certain bacteria use sunlight to turn CO2 and water into sugar, providing energy for themselves and all organisms further up the food chain.

But without sunlight, the bottom of the vent food chain had to find another energy source. Specially adapted bacteria, and another ancient life form called Archaea, can use hydrogen sulfide, iron or other chemicals pouring from beneath the earth’s crust to produce their own energy and support life around vents - ecosystems based on heat and chemical energy from the earth. Often in science unexpected findings lead to new ideas and areas of speculation. Some scientists now believe vent communities may be modern day models of how life started on earth. They might also offer an alternate model for life on distant planets.

Deep sea vents still have much to teach us. The extreme conditions slow the process, and require specialized observation and collection methods using fiberoptic devices, robot vehicles and other deep submersibles. Knowing that more people have visited outer space than the deepest parts of the oceans helps me realize how great the challenges are.

Lifelong Oregonian Fred Schubert, a The Dalles biologist, has a longstanding interest in general science and science writing. Feel free to submit any comments on this article or suggestions for new topics to fcscience @qnect.net.

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