EARTH 222 Lecture 25: Hydrothermal Systems
23 Apr 2017
School
Department
Course
Professor
April 3, 2017
Hydrothermal Systems
•Background biology
•Prior to 1977…
•Biologists thought that photosynthesis supported all life on Earth
•Organisms in the deep sea ate only what little debris from the surface waters
•Scarce food meant that diversity of limited
•Most animals were scavengers on the ocean bottom or filter feeders
•Basis for life
•Photosynthesis
•Dominant form of primary production in the ocean and on land
•Requires water, CO2, nutrients, and energy
•CO2 + H2O —> CH2O + O2
•Respiration
•Energy released fuels life processes for autotrophs and heterotrophs
•Requires organic matter and O2
•CH2O + O2 —> CO2 + H2O
•The hydrothermal discovery
•In 1977, researchers aboard Alvin found an entire ecosystem at the Galapagos Ridge, far
removed from the direct influence of the Sun
•After temperature-sensitive equipment returned small temperature changes at one site
along the Rift, cameras sent to the same site returned with pictures of heaps of clam shells
•Further submarine dives to vents have revealed temperatures as high as 464ºC and a
variety of unusual organisms
•First reactions
•This was potentially the greatest biological discover of the 20th century
•Some unanswered questions
•What did all of these organisms eat considering food is so scarce in the deep sea?
•Were these organisms related to anything we already knew about?
•Basics of hydrothermal vents
•Hydrothermal circulation = heat driven circulation of water
•Process
•Sea water sinks through cracks in the sea surface
•This seawater is heated by the warm lithosphere, causing convection
•Hot water at >350ºC dissolved reduces chemicals
•Vent fluids are ejected into the deep oceans
•Types of hydrothermal vents
•Diffused flow vents
•Discharge warm 2-23ºC water that contains abundant hydrogen sulfide, nitrate,and
oxygen
•Black smokers
•Discharge very hot water (~350ºC) at high flow rates
•The temperature of water in black smokers—350ºC—is greater than the boiling
point of water on Earth’s surface (100ºC)
•The high pressures at the bottom of the ocean prevents the 350ºC water in black
smokers from boiling
•No oxygen nitrate, but high metal concentrations (Fe and Mn)
•Metal leaches from crust
•Superheated water meets cold deep water
