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During the transit...

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Calling OBS home before the weather

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Yesterday, we finished recovering 29 ocean bottom seismometers deployed along the Emperor Seamount Chain, thus completing our field program in the Emperor Seamount Chain.We were blessed with a long period of excellent weather for collecting data on the 15-km-long seismic streamer and for most of the OBS recoveries.Good weather is particularly important for the latter.Despite all of the technology that enables us to put a seismometer on the seafloor in water depths of 6300 m (~19,000 ft!) and send them commands to come back to the ocean surface, our method of fetching them from the ocean onto the ship is quite basic, but still impressive! The ship’s mates drive this large vessel right up next to the floating OBS, and people reach out and hook the OBS from the starboard deck using a long stick!We then use a crane to hoist them out of the water. This procedure becomes much more difficult in rough weather. Maneuvering the vessel is more challenging when the winds and waves pick up, and de…

The Emperors among us

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Finishing the seismic reflection acquisition part of our experiment, we find ourselves south of Jimmu Guyot and near Suiko Guyot. The term ‘guyot’ refers to a flat top seamount that was first named by Harry Hess, a pioneer in developing our current understanding of plate tectonics. These features have a similar morphology to the plateaus found in the Western United States with both having a flat terrain on top that is raised above with surrounding areas often by steep slopes. The Hawaii-Emperor Seamount Chain is a great example of the formation of guyots along volcanic chains. Active volcanism is found on the youngest in the chain, currently at the Big Island of Hawaii which sits atop the central Hawaiian hotspot, a small spot in the plate that fuels the volcano from great depths. As the Pacific Plate slowly but steadily moves to the northwest, it carries the islands away from the hotspot, and as they move further away from their main fuel, the island and their volcanoes become extin…

In the fog...

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For the last few days, we have had calm seas and been ensconced in a thick fog much of the time. Right now, this doesn't pose any problems for our science operations - we are cruising along and acquiring seismic reflection data, which can illuminate the subsurface just fine, fog or no fog.  But the fog is starting to make everyone on the ship a little crazy!   Normally one is treated to expansive ocean views at sea, but instead we get to see this:
Perhaps even more disconcerting, the ship sounds a special fog horn at regular intervals to alert other ships that we have limited maneuverability since we are towing equipment. It consists of one long horn followed by two shorter ones. It is very loud.  Everyone on the ship will tell you that this horn must be located right outside their cabin.

We can live with it for now, but soon we will transition back to OBS work. When its time to pick them up, it would be super helpful if we could actually see more than 100 m from the ship!

Donna S…