Monday, September 20, 2010
Hydrothermal activity blasts out sediment
Ted Moore is an Emeritus Professor in the Department of Geological Sciences at the University of Michigan. This position is given to a professor who has retired but is highly regarded by the department. With this title Ted has some office and research space which allows him to continue research, which he has very actively. Since he retired he has sailed on research cruises, completed lecture tours and written papers. Ted was a pioneer in the field of paleoceanography and was integral to a massive community-based research initiative called CLIMAP, whose purpose was to map out the temperatures on the planet during the last ice age, 21 thousand years ago. Ted has a speciality in micropaleontology looking a a zooplankton group known as radiolaria. Radiolaria are a amoeboid protozoa that produce intricate skeletons made of silica.
Image of radiolaria from Nest Labs at the University of Dayton.
Ted will be talking about the sediments that are deposited in the equatorial region and their interaction with hydrothermal fluid. The classic hydrothermal vent in the ocean is associated with volcanism at mid ocean ridges (sea floor spreading centers at divergent boundaries). However a recent estimate (Bekins et al. 2007 - in resources) suggests that hydrothermal fluids exiting outcrops (cliffs) of basement (meaning the rock underlying sediment) sea floor (basalt generated at mid ocean ridges) may account for 75% of the hydrothermal outflow in the equatorial Pacific. These environments have become the focus of interest by scientist interested in microrganisms - these environments maybe similar to those found on other planets and the work these microrganisms do might be very important to the formation of mineral deposits.
Cartoons illustrating the development of pits over a bedrock outcrop. (a-c) show where flanking basins have approximately the same thickness of fill and (d-f) show where the basin fill is asymmetrical.
Ted came up with the model by which pits form in deep sea sediments allowing the discharge of waters circulating through the ocean crust. This water is able to remove heat from the cooling newly formed ocean plate explaining the low heat of the equatorial Pacific plates. The model suggests that the sediments overlaying the bedrock outcrop are dissolved by the water being discharged leaving behind sediment pits. These hydrothermal discharges may also be involved in the diagenetic alteration of siliceous sediments such as those which form from the remains of radiolaria. At high temperatures the silica remains of organisms convert to porcelanite and chert as the crystal structure of the opaline or biogenic silica changes.
Chert or jasper in the jasper conglomerate outside the CC Little building