The Okeanos Explorer left Honolulu on July 10th on an exploratory ocean mapping cruise to the Johnston Atoll region of the Pacific Remote Islands Marine National Monument. This cruise is the first in the four-cruise series that comprise the “Hohonu Moana: Exploring the Deep Waters Off Hawai’i” expedition. During the current cruise we are continuously running three different sonar systems to map and characterize the seafloor, shallow sub-seafloor geology, and the water column. Most of the Monument has never been mapped using sonars, and this work will provide novel insights into the geologic features and marine habitats in this large marine protected area.
A calibration of the multibeam sonar was completed on the first day of the cruise, after which the ship completed a 700 mile transit to the boundary of the Monument. Inside the monument, the ship mapped a 142-mile segment of the Horizon Tablemount – a long flat-topped ridge feature. The ship then voyaged south mapping several seamount features and passing directly by the remote U.S. Fish and Wildlife Service Refuge on Johnston Atoll. The ship is currently mapping a large portion of the Johnston Seamounts located to the south of Johnston Atoll. The seafloor maps being made on this cruise will be used to help select the locations of remotely-operated vehicle dives when the ship returns to this area during Leg 4 of the expedition.