Treasures of the Deep

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When you think of legendary cities hidden beneath the ocean waves, Atlantis is undoubtedly the first name that springs to mind. Yet the ocean floor is home to a remarkable array of elaborate structures, many of them created not by humans but by natural processes. In 2000, a formation of towering pillars and columns was discovered in the Atlantic Ocean and christened the Lost City. It has since garnered significant research and media attention and was prominently featured in the IMAX film ‘Aliens of the Deep’.

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The Lost City is located halfway between Florida and the African coast, 15 kilometers west of the Mid-Atlantic Ridge. This ridge, which runs roughly north-south along the length of the Atlantic Ocean, is the rupture zone formed as the tectonic plates that support North America and Eurasia/Africa gradually drift away from each other. Through this crack bubbles hot magma, which cools upon contact with seawater and forms basalt – a black igneous rock commonly associated with volcanic regions.

atlanticThe Mid-Atlantic Ridge can be seen as a brown-green band running vertically through this satellite image 

Forming the foundation for the Lost City site is the Atlantis Massif – a monumental dome that towers more than 4,250 meters above the ocean floor. The top of the dome, where the site is found, is located 750 to 900 meters below the ocean surface. The seamount is composed of peridotite, a rock formed in the Earth’s mantle. Water heated by the nearby magma source rises from vents in the rock. As it comes into contact with seawater, the mineral-laden fluid reacts and releases hydrogen, methane, and minerals including calcite and aragonite. Over thousands of years, mineral accumulation forms large chimney structures that resemble inverted stalactites – the ‘icicles’ often found on cave ceilings.

smallerstructure_med Lost_City_(hydrothermal_field)02lostcity3651-1022_med

Hydrogen and methane act as sources of energy for bacteria, allowing them to transform mineralized carbon into the organic compounds needed for life. Temperatures in the range of 40 to 90 degrees Celsius are able to sustain diverse ecological communities, including snails, crabs, and corals. 58% of the fauna inhabiting this vent environment are not found anywhere else on Earth. Because of the chemical composition of the rocks that make up the seamount, the Lost City creates a unique habitat, distinct from more common black and white smokers – deep sea vents that release sulfur- and carbon dioxide-rich mineral waters respectively.

Dating has shown Lost City deposits to be over 150,000 years old – older than any hydrothermal system studied to date. Undisturbed, the vents have continued to harness the heat of the Earth even as continents froze and thawed through multiple glaciations. This site grants scientists insight into the processes and environments that allowed the birth of the earliest forms of life on our planet. Long before plants and algae could harness the energy of the sun, such systems would have provided one of the few sources of energy and molecular buildings blocks required for life to thrive.

argusl_600During the 2005 expedition to the Lost City site, footage and data from this ROV (remotely operated vehicle) were transmitted to research facilities in real time

Check out this cool 10-second clip showing site bathymetry (seafloor topography) and footage:

Until next week, be warned: you may have just sustained a lethal dose of mostly harmless scienceIf you enjoyed this article, please comment below and share with your friends! Feel free to follow me on WordPress or on Twitter @harmlessscience (just click Follow on the right sidebar). Thanks for reading!

All photographs courtesy of the University of Washington

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