FeMO3 Dive Cruise 2008
Report Day 08 -- Monday 29 September 2008 -- Mariprofundus ferrooxydans
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FeMO3 Dive Cruise 2008 |
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Clara Chan has grabbed some bacteria from the slurp containers and put the “slurpings” into microscope slides that have special chambers in them. The chambers are grooves into which the bacteria, some filtered seawater and some nutrients are added in the hopes that the bacteria will survive and grow under the microscope. Looking through the scope I see a short, thin, hair-like structure that branches. At the end of each branch is a bright speck that catches the light – a bacteria cell. It’s not easy to see unless I move the focus up and down and follow the branching, but then the structure is obvious and repeated.
Clara explains that the branching structure is a thin thread of iron oxide bound with a polysaccharide – like a trail of rusty mucous. The bacteria gets energy by converting dissolved iron to iron oxide, but iron oxide is solid and unusable so it must be gotten rid of. So the iron oxide is expelled. The branching is explained as cell division or reproduction. A single cell grows and expels its little rusty trail until it divides. When it divides the two daughter cells go their separate ways each leaving their own trail of rust. This pattern of cell division and branching can be repeated for several generations, which explains the many branchings I see through the microscope.
Jason has returned to the deep site called Ula Nui for a sonar mapping survey and a transect up the east rift of Loi’hi. The Hawaiian volcanoes grow by erupting lava in flows in successive layers that build up to enormous heights. The Mauna Kea volcano rises to nearly 14,000 feet altitude, but with its altitude measured from sea level, not the seafloor. If the pile of lava were measured from the seafloor where the mountain started, the total height of that pile is 30,000 feet. Measured from the seafloor Mauna Kea is the tallest mountain on Earth. To say that Mauna Kea and Mauna Loa are “only” 13,000 foot mountains is like saying a 7 foot basket ball player standing in a 4 foot ditch is only 3 feet tall. The amount of lava erupted is enormous.
That column of lava pushing up from the Earth’s mantle and through crumbling layers of basalt inflates the mountain stretching and cracking it. These cracks are rifts. An eruption might start at the summit of the mountain, but within days or weeks the lava finds a weakness in the flank of the volcano and begins to spurt out lower down on the side. The weakness here is the rift; it looks like a crack running down from the summit into the ocean. The internal plumbing between the summit and the rift can be so well connected that as the lava begins to pour out the side the summit eruption slows and stops.
Loi’hi erupted massively in 1996, spewing a plume of volcanic gasses into the ocean at 1,000 meters depth that could be tracked all the way to California. Then the summit collapsed into a series of pits that left part of the flank as the new summit. The volume of the mountain that disappeared during the collapse is about ½ a cubic kilometer or nearly 500 million tons of lava.
Despite the huge amount of lava that had to erupt to cause the collapse, there is hardly any fresh, glassy basalt found near the summit. Instead the most recent looking lava we’ve seen appears to be far down the south rift. Mark Kurz directs Jason to survey up the south rift from Ula Nui to map the recent flows and collect samples from them.
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