FeMO4 Dive Cruise 2009
Report Day 11 -- Sunday 11 October 2009 -- Mapping the Ocean Floor
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FeMO4 Dive Cruise 2009 |
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I wake up at sunrise to the sound of the winch lowering the CTD into the water. It is a beautiful sunrise in the middle of the Pacific!
After the CTD comes back up, Jason descends to the Lo’ihi crater. The goal of this dive is to map a small area of the crater. I discover that mapping involves moving Jason back and forth numerous times across an area. As Jason moves, the boat follows so in essence, Jason is leading the boat. Jason sends out sonar signals that bounce off of the formations on the ocean floor. The depth of each section of the area that is being mapped is determined by the length of time it takes for the signal to return. I am curious what a topographical map of the Lo’ihi crater looks like. In the FeMO 2009 files I find some interesting maps of the Lo’ihi summit. The first map is a three-dimensional view of Lo’ihi. The dark brown area is the summit which contains three craters. The blue areas are almost as deep as the surrounding ocean floor.
Next, I find an actual topographical map of Lo’ihi, but then I learn that maps of underwater features are called Bathymetric, not topographic. This is an aerial view looking down on the summit. The brown areas are the shallowest and the blue areas are the deepest.
On the 2009 FeMO expedition Jason has primarily visited Pele’s Pit and FeMO Deep. The FeMO scientists have spent a great deal of time visiting, photographing, and sampling Pele’s pit because it is currently the most active area of the Lo’ihi summit. They tell me that it hasn’t always been that way. Prior to the earthquake in 1995 Pele’s Pit was actually Pele’s Peak. The volcano erupted and the peak collapsed and formed a pit crater. Pele’s Peak became Pele’s Pit. I wonder if some day Pisces Peak will become Pisces Pit?
The Pit of Death also has an interesting history. It received this ominous name because the first time scientists peered into the pit they saw endless mushy carcasses of dead animals lying at the bottom of the pit. All animals that entered the pit died within seconds. Scientists discovered that the bottom of the pit was heavily infused with carbon dioxide gas escaping from the vents, and very little oxygen. Unwary animals would arbitrarily swim into the pit and immediately become asphyxiated by the carbon dioxide. Their bodies would fall to the bottom of the pit and decompose at an extremely slow rate due to the lack of oxygen. Since the 1995 earthquake, carbon dioxide has ceased to heavily infuse the pit so animals no longer swim down to their death.
Jason continues his mapping effort in Pele’s pit, moving back and forth and back and forth until he is done. Jason will come back up in the wee hours of the morning after a long monotonous day at work walking back and forth across the ocean floor.
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