Today’s dive will be to a depth of approximately 2,440 meters (~8005 feet). “Ridge” Seamount is in the southern part of the Johnston Atoll Unit of the Pacific Remote Islands Marine National Monument, where no previous mapping or ROV surveys have been conducted. Based on satellite altimetry data, the area has a complex distribution of seamounts, some of which may be guyots while others may be more conical in shape. This seamount was mapped two nights ago and found to have a ridge shape running northwest to southeast. Deep Discoverer will dive just below its summit and come onto the crest while searching for coral and sponge communities.
The ROVs should be in the water at approximately 8:30 AM, HST (2:30 PM, EDT) and will go to a starting depth of ~2,100 meters (~6,890 feet). We will explore a rift zone ridge extending southeast from the east side of the guyot we surveyed yesterday, “Wetmore” Seamount. This area is presumed to be manganese-encrusted. We will be looking for high-density deep water coral and sponge communities as well as rocks to sample. Ridges act as barriers to bottom current flow and their crests are locations where currents accelerate, which is where the corals and sponges are often most heavily aggregated. Ridges are also sites where basalt can be found and are, therefore, desirable locations for obtaining rocks for dating seamounts.
ROV Deep Discoverer will dive on a rift zone ridge extending SE from Wetmore Seamount, a guyot located near Johnston Atoll, beginning at a depth of 2,600 meters (~8,530 feet). Ridges act as barriers to bottom current flow and their crests are locations where currents are accelerated, which is where the corals and sponges are often most heavily aggregated. Ridges are also sites where basalt can be found and are, therefore, desirable locations for obtaining rocks for dating seamounts. Our planned start time is 8:30 AM, HST (2:30 PM, EDT). For more information about this expedition, go to:
Today’s dive will be on a manganese-crusted guyot; its summit edges may have deep water coral and sponge communities. This particular site is on a potential “pancake volcano” created by secondary volcanism that should yield valuable rocks for geologic aging. The site is also along the edge of the summit that was likely a Cretaceous reef. The dive will start at approximately 1,600 meters (~5,250 feet) and should start at 8:30 AM, HST (2:30 PM, EDT). At approximately 4:00 PM, HST (10:00 PM, EDT) we will explore the water column. We hope to provide data on the distributions, abundances, and behaviors of a variety of midwater animals.
The maintenance for the cable supplying power and communications to ROV Deep Discoverer has been completed and we are diving again. Today’s dive will take place on an unexplored area of “Edmondson” Seamount and will begin at about 8:30 AM, HST (2:30 PM, EDT) at a depth of approximately 1300 meters (~4265 feet). This site was selected for its unusual geology. This feature is believed to represent secondary volcanism after the guyot it is on sunk well below the surface. While secondary volcanism is common, and is seen on many seamounts in the Johnston Atoll area, this particular example is much larger than any others and covers much of the summit of the guyot it is on. The dive track will be along a sharp ledge at the top of the feature where deep water corals and sponges may be found. For more information about this expedition, go to:
The Engineering Team is continuing to troubleshoot and repair ROV Deep Discoverer. There will be no dive for July 20. Instead, we will spend the day mapping. We plan to dive again on Friday, July 21. For more information about this expedition, go to:
In order to give the Engineering Team additional time to troubleshoot and repair the Deep Discoverer remotely operated vehicle, the dive for July 19 has been cancelled. We will spend the day mapping. Stay tuned for additional information regarding the status of diving on Thursday, July 20.