If you dive into the deep, you may find the ocean not as dark/silent as you thought. Back to the year 1977, a group of scientists from Woods Hole Oceanographic Institution saw photos of shimmering water drifting out of the seafloor along the Galapagos Rift. This was the first discovery of a hydrothermal vent, and it has since changed our understanding of the planet.
As you’ve seen in Week 1 of the course, hydrothermal venting occurs when seawater penetrates into the ocean crust, becomes heated, reacts with the surrounding rock, and then rises to the seafloor as fluid and gas. Forty years of exploration has yielded an inventory of more than 500 active vent fields (according to Baker et al., 2016). They are often thousands of meters below the surface of the ocean, along the large volcanic mountain ranges called the mid-ocean ridges.
These submarine hot springs are a major gateway for the exchange of heat and chemicals between the solid earth and the deep ocean. The chemicals coming out of the hydrothermal vents could be liquids, particles or gases, and include inorganic compounds as well as organic molecules. The leaky vents play a potentially important role in the cycling of these chemicals in the oceanic inventory.
You have noticed the fascinating life in hydrothermal vent ecosystems – can you imagine how these organisms survive in the high pressure, high temperature, and toxic environments? They don’t even need sunlight, as chemical energies are supplied through a process called chemosynthesis. These also provide insights into origins of life on Earth.
In the year 1985, a group of scientists from Cambridge participated in a cruise that produced the first photographs of a hydrothermal vent called the TAG (Trans-Atlantic Geotraverse) which is the first vent discovered on the Mid-Atlantic Ridge. The spreading rate of the Mid-Atlantic Ridge is slow (less than 40 mm/yr), and this means such hydrothermal phenomena is just not limited to fast-spreading oceanic ridges (Rona et al., 1986).
In the 1990s, a multidisciplinary scientific investigation of the mid-ocean ridges was conducted by a list of British institutes (BRIDGE Programme, https://wikipedia.org/wiki/British_Mid-Ocean_Ridge_Initiative). Many scientists and research centres around the UK contributed to this programme, and cruises explored the North Atlantic, Southwest Atlantic, and Southwest Pacific. ”Every area- geophysics, geochemistry, biology and technology, had success.” But does this mean the hydrothermal exploration is complete? Not really. There are still questions to answer- about how many hydrothermal vents, about organisms that surround the vents, about the chemical fluxes transported to the oceans.
Here is a link from NOC website showing the research ships, and you must have been aware that they are the primary method of oceanographic observation http://noc.ac.uk/facilities/ships Each research expedition has a cruise ID (for example, DY is for Discovery and JC for James Cook). The maiden scientific voyage of James Cook was in 2007, and after 12 years, the JC180 expedition has now finished. Behind these numbers, it was the scientific missions that have been achieved. The missions have always considered hydrothermal exploration as important. I was impressed when I was exploring the inventory of research cruises onboard James Cook, here I’d like to list some of what I’ve read:
JC042 (2010-01-07 to 2010-02-21): the exploration of deep-sea vents around Antarctica;
JC044 (2010-03-25 to 2010-04-22): the discovery of the world’s deepest hydrothermal vent in the Cayman trough;
JC080 (2012-12-02 to 2012-12-30): revisiting Southern Ocean vents that teem with life http://hotventscoldocean.noc.ac.uk/;
JC082 (2013-02-06 to 2013-03-08): revisiting hydrothermal vents in the Caribbean http://intothecaymanabyss.noc.ac.uk/
JC138 (2016-07-08 to 2016-08-24): exploring seafloor massive sulphide deposits around TAG https://bluemining.eu/research-cruise-2-james-cook-138/
JC156 (2017-12-20 to 2018-02-03): exploring iron supply from Mid-Atlantic Ridge https://ga13fridge.wordpress.com/
The vents are hot, the sciences (and people who are devoted to sciences) are cool. What’s going to be the next expedition?