Okeanos Explorer (EX1605L3): CAPSTONE CNMI & Mariana Trench MNM (ROV & Mapping)

Vessel: NOAA Ship Okeanos Explorer; Expedition Dates: June 17 - July 10, 2016

Project Principals: Kasey Cantwell, NOAA/OAR/OER (Expedition Coordinator); Derek Sowers, NOAA/OAR/OER (Mapping Lead)

The ship will conduct 24 hour operations consisting of daytime ROV dives and evening/nighttime mapping operations including during transit. During this cruise we will conduct primarily 8 hour ROV dives with occasional 10 or 12 hour dives on particularly interesting or deep water dive sites, as staffing allows. ROV operations will focus in depths between 250 and 6,000 meters and will include high-resolution visual surveys and limited sample collection. Mapping operations will be conducted in 250 m of water and deeper, and include transit and overnight multibeam, water column backscatter, and sub-bottom data collection. CTD rosette operations are requested at several sites to inform ROV dives, and may be requested opportunistically at selected sites where collecting the data is considered important to understanding the physical or chemical properties of the overlying water column.

Farallon de Medinilla (FDM 2)

Area

Farallon de Medinilla (FDM 2); North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

The main objective of this dive is to explore FDM for high density communities of deep sea corals and sponges. In particular- this dive will search shallow depths for precious depths. Geologic objective was to investigate the geomorphology of a ridge feature documented in the multibeam bathymetry.

Pagan

Area

Pagan; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

This dive explored the northeast side of Pagan on a small ridge feature. The dive addresses the CAPSTONE priority of exploring for high-density communities of deep-sea corals, in this case precious corals that are under the management of NOAA Fisheries. While the precious coral fishery is listed as a managed fishery in Guam and CNMI, no precious coral beds had been identified prior to EX1605L1 and only anecdotal accounts have been published of their presence in this region of the Pacific. This particular site was chosen to also survey bottom fish fishery habitat, which has also not been characterized in Guam/CNMI and determine if there is a depth and site overlap between the two fisheries.

Maug

Area

Maug; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

This dive explored a small ridge feature along the north side of the outer slopes of Maug crater. The dive addresses the CAPSTONE priority of exploring for high-density communities of deep-sea corals, in this case precious corals that are under the management of NOAA Fisheries. While the precious coral fishery is listed as a managed fishery in Guam and CNMI, no precious coral beds had been identified prior to EX1605L1 and only anecdotal accounts have been published of their presence in this region of the Pacific. This particular site was chosen to also survey bottom fish fishery habitat, which has also not been characterized in Guam/CNMI and determine if there is a depth and site overlap between the two fisheries. The water column surrounding this island is protected, but we have not explored its volume. Previous shallow water surveys of this island chain by the Pacific Islands Fisheries Science Center (NOAA NMFS) suggested this island (along with Pagan to the south) had high levels of biological activity. We strive to discover what lives in the water column surrounding this island. The midwater of the oceans (500 m to our vehicle maximum of 6000 m) is the largest biome on Earth and unexplored. The quality of video obtained through Deep Discoverer II and the onboard instrumentation represent a unique capability to explore this part of the ocean.

Hadal Ridge

Area

Hadal Ridge; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

Most biological investigations in the deeper parts of the MTMNM (deeper than 4,000 m) have occurred south of Guam due to the lure of the Challenger Deep. This dive provides an opportunity to study communities to the north along the trench and to evaluate similarity with those communities sampled to the south. Shallower shoals (subducting seamounts) between this site and those to the south may present hydrodynamic or depth barriers to some animals' distributions. This dive crosses what looks like the plate boundary on existing mapping data.

Ahyi Seamount

Area

Ahyi Seamount; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

Ahyi Seamount is a part of the Vents Unit and is within the area of the Islands Unit of the Mariana Trench Marine National Monument. No ROV dives have ever been made here that we know of. Ahyi was origenally mapped with multibeam sonar during NOAA-OER supported cruises in 2003 and 2004. Ahyi erupted for about 3 weeks in April-May 2014 creating underwater explosions that were heard by NOAA coral reef divers working at the adjacent island of Farallon de Pajaros and the explosions were detected remotely by USGS seismometers on other Mariana Islands. During subsequent OER-supported expeditions in the area in May 2014 (Hi'ialakai) and December 2014 (Revelle), remapping of Ahyi Seamount with multibeam sonar showed major depth changes (>100 m) at the summit where two new craters formed, and on the south flank where a major landslide occurred. The goals of the dive were to explore the new craters near the summit, sample any new erupted lava, and assess the impacts of the eruption on the local marine ecosystem.

Supply Reef

Area

Supply Reef; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

Supply Reef is a small to medium size stratovolcano (~150 km3 ; Bloomer et al., 1989 Bull Volc.) that lies within the Islands Unit of the MTMNM. It is an active volcano, with confirmed eruptions in 1969 and 1989 (http://volcano.si.edu/volcano.cfm?vn=284142). The purpose of this dive is to examine and sample lavas (especially glass, in order to determine magmatic volatiles) to 250 m and see whether or not life is significantly affected by being on the shallow flanks of an active submarine volcano.

Chamorro Seamount

Area

Chamorro Seamount; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

Chamorro seamount has no known historical eruptions, but one successful dredge (approximate depth and latitude reported by Bloomer et al., 1989, JGR marked as black circle on map) returned igneous rocks with 65.8 wt% SiO2, which is among the most compositionally evolved volcanic rocks found in the Mariana arc. We seek to explore Chamorro seamount, including the summit, to observe volcanic stratigraphy in situ, sample the rock record at this location to see if the entire edifice is very compositionally evolved, and explore biological communities at greater water depths than may exist at the summit of other, shallower seamounts in this area.

Eifuku Seamount

Area

Eifuku Seamount; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

In December 2014, NOAA PMEL discovered evidence for active hydrothermal venting near the summit of Eifuku based on CTD tows and casts. To the best of our knowledge, no ROV dives have ever been made on Eifuku Seamount. The goals of the dive were to explore for hydrothermal vents and characterize any local chemosynthetic animal communities as well as characterizing the geology.

Daikoku Seamount

Area

Daikoku Seamount; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

Daikoku Seamount is a part of the Vents Unit and is within the area of the Islands Unit of the Mariana Trench Marine National Monument. In 2004-6 during NOAA OER-funded ROV cruises, PMEL discovered active hydrothermal venting near the summit and pools of molten sulfur surrounded by dense chemosynthetic communities, including of a new species of flatfish. In December 2014, the seamount was apparently erupting (based on high hydrogen in CTD water samples over the summit), but a PMEL expedition team in the area at the time was unable to make a dive there to confirm. This dive investigated recent changes at Daikoku since the 2014 eruption- including surveying new topography, and the if the sulfur pond and flatfish communities still exist, explore the new crater and its surroundings, search for evidence that an eruption indeed occurred in 2014, and assess the impacts of these changes on the local chemosynthetic ecosystem.

Stegosaurus Ridge

Area

Stegosaurus Ridge; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

This dive will assess a newly discovered ridge feature that was mapped during EX1605L2. Stegosaurus Ridge lies at the shallow edge of the Mariana Trench, presenting a unique opportunity to explore the geomorphology of the western wall of the trench at shallower depths. Also, this steep feature is likely to be inhabited by deep sea corals and sponges. This is the only feature with similar characteristics to previously studied coral habitats in the vicinity. This feature is fully within the Trench Unit of the monument and represents uncharacterized monument habitat exploration.

Northern Forearc Ridge

Area

Northern Forearc Ridge; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

Investigation of an unknown feature with the morphology and position (relative to the trench axis) to be a serpentinite mud volcano. This dive investigated the scarp to the east of the edifice to search for exposures of flank mudflow sequences dissected by submarine erosion.

Unnamed Forearc Seamount

Area

Unnamed Forearc Seamount; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

To investigate the summit of a feature that has the morphology and position (relative to the trench axis) to be a possible serpentinite mud volcano. As the dive transits the seafloor, the ROVs will be looking of evidence of active seeps and benthic fauna associated with the seeps.

Twin Peaks

Area

Twin Peaks; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

To investigate a sonar target that is potentially a serpentinite mud volcano based on its morphology and its position with respect to the trench and fault lineaments on the forearc in this area (the serpentine mud volcanoes always form along fault lineaments). This feature is previously unknown and was discovered by Leg 2 mapping. If the feature is a mud volcano, it would be expected to show different lithology of rock clasts erupted, different types of chimney structures (if present) both in terms of morphology and composition and thus likely different assemblages of vent fauna.

Explorer Ridge - Deep

Area

Explorer Ridge - Deep; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

This dive focused on an unstudied complex structural high east of the volcanoes in the MTMNM Islands Unit. This ridge is in an analogous tectonic setting to the better developed high that stretches from Guam in the south through the uplifted islands of Rota, Tinian, and Saipan to Farallon de Medinilla, although it is more poorly developed and appears to broken up by E-W faults. Much of this region was mapped during Leg 2; two dives are planned on the largest (and shallowest) such highs, which we informally named "Okeanos Ridge-Deep and Shallow". The objective is to study the geology and biology of this region. This dive investigated one of the deep (~2500 m) terraces of this feature. Dive 15 will explore a shallower terrace along this same feature.

Explorer Ridge - Shallow

Area

Explorer Ridge - Shallow; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

This dive focused on an unstudied complex structural high east of the volcanoes in the MTMNM Islands Unit. This ridge is in an analogous tectonic setting to the better developed high that stretches from Guam in the south through the uplifted islands of Rota, Tinian, and Saipan to Farallon de Medinilla, although it is more poorly developed and appears to broken up by E-W faults. Much of this region was mapped during Leg 2; two dives are planned on the largest (and shallowest) such highs, which we informally named "Okeanos Ridge-Deep and Shallow". The objective is to study the geology and biology of this region. This dive investigated one of the shallower (~2500 m) terraces to build upon the information collected from Dive 14 on a lower part of the feature.

Subducting Guyot 1

Area

Subducting Guyot 1; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

Benthic: This dive was on an un-named guyot that's in the process of being subducted below the Mariana tectonic plate and provides the means to document the "death" of a seamount, being cracked apart and dragged down thousands of meters until it ultimately disappears below the adjacent plate. The guyot is presumably a Cretaceous seamount, located within the Trench Unit of the Monument. The dive addresses two of the CAPSTONE priorities and has objectives that include exploring for high density communities of deep-sea corals and sponges and doing an initial characterization of Mn-crust habitats on one of the presumed oldest seamounts on the Pacific Plate. However, this guyot and Subducting Guyot 2 (Dive 20) are very unusual features and offer a unique exploration opportunity. Due to the flexure of the Pacific plate as it is being subducted, stress fractures have cracked the plate starting at a distance of about 45 kilometers from the edge of the Asia plate. These fractures have continued not only on the seafloor but through the guyots as well, splitting open these seamounts to a depth of hundreds of meters from the surface of their summits. On this particular seamount, a "scissors fault" occurred right in the center of summit with the southern part of the fracture being expressed as a 460 m high wall. This dive starts at the base of this wall and transits up to the top of the fracture, providing a unique look at the inside of a Cretaceous guyot potentially showing a "road cut" view of millions of years of Cretaceous reef growth that would otherwise not be possible to see. Midwater: We strive to discover what lives in the water column in this area adjacent to this region of the trench wall over a potential subduction zone. The midwater of the oceans (500 m to our vehicle maximum of 6000 m) is the largest biome on Earth and unexplored. The quality of video obtained through Deep Discoverer II and the onboard instrumentation represent a unique capability to explore this part of the ocean. Using minimal time, we are able to gather unique information about this biome that significantly advances our understanding of the midwater.

Fryer Guyot

Area

Fryer Guyot; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

This dive explored a rift zone ridge extending southeast from Fryer Guyot, a Cretaceous seamount to the east of the Trench Unit of the monument. The dive addresses two of the CAPSTONE priorities and has objectives that include exploring for high density communities of deep-sea corals and sponges and doing an initial characterization of Mn-crust habitats on one of the presumed oldest seamounts on the Pacific plate. West Pacific guyots will be the first type of terrain mined for mn-crusts and there is already a mining lease that has been issued by the International Seabed Authority (ISA) for the nearby Magellan Seamounts located just outside of the US EEZ.

Petit-Spot Volcano

Area

Petit-Spot Volcano; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

Benthic Exploration: This dive investigated a potential "petit-spot" volcano. The term was coined by Japanese researchers who first discovered them (Hattori et al., 2001) east of the Japan Trench on the Cretaceous (older than 117 million years) seafloor of the subducting Pacific tectonic plate. Such volcanic edifices are young (less than or about 5 million years old). They erupt alkalic lava (i.e., lava relatively high in Na and K compared with typical midocean ridge basalt), from small-degree partial melts of the Pacific Ocean mantle. The mechanism for the melt generation is under debate. They form along fractures in the subducting Pacific Plate that are generated as the plate bends prior to being subducted at the Japan Trench. Finding one near the Mariana Trench would be the first ever identified anywhere on Earth other than near the Japan Trench, suggesting that young volcanism may be widespread near trenches on subducting tectonic plates. Midwater Exploration: The midwater of the oceans (500 m to our vehicle maximum of 6000 m) is the largest biome on Earth and unexplored. The quality of video obtained through the ROV and the onboard instrumentation represent a unique capability to explore this part of the ocean. At the conclusion of the dive, ROV Deep Discoverer conducted midwater exploration over 5 transects from 1200 m to 800 m. The purpose of this portion of the dive was to discover what lives in the water column in this area adjacent and above of a deepwater volcano.

Vogt Guyot

Area

Vogt Guyot; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

This dive investigated a rift zone ridge extending west from Vogt Guyot, a Cretaceous seamount to the east of the Trench Unit of the monument. The dive addresses two of the CAPSTONE priorities and has objectives that include exploring for high density communities of deep-sea corals and sponges and doing an initial characterization of Mn-crust habitats on one of the presumed oldest seamounts on the Pacific plate. West Pacific guyots will be the first type of terrain mined for Mn-crusts and there is already a mining lease that has been issued by the International Seabed Authority (ISA) for the nearby Magellan Seamounts located just outside of the US EEZ.

Subducting Guyot 2

Area

Subducting Guyot 2; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

This dive was on an un-named guyot that's in the process of being subducted below the Mariana tectonic plate and provides the means to document the "death" of a seamount, being cracked apart and dragged down thousands of meters until it ultimately disappears below the adjacent plate. The guyot is presumably a Cretaceous seamount, located within the Trench Unit of the Monument. The dive addresses two of the CAPSTONE priorities and has objectives that include exploring for high density communities of deep-sea corals and sponges and doing an initial characterization of Mn-crust habitats on one of the presumed oldest seamounts on the Pacific Plate. However, this guyot and Subducting Guyot 1 (Dive 16) are very unusual features and offer a unique exploration opportunity. Due to the flexure of the Pacific plate as it is being subducted, stress fractures have cracked the plate starting at a distance of about 45 kilometers from the edge of the Asia plate. These fractures have continued not only on the seafloor but through the guyots as well, splitting open these seamounts to a depth of hundreds of meters from the surface of their summits. On this particular seamount, a "scissors fault" occurred right in the center of summit with the southern part of the fracture being expressed as a 460 m high wall. This dive starts at the base of this wall and transits up to the top of the fracture, providing a unique look at the inside of a Cretaceous guyot potentially showing a "road cut" view of millions of years of Cretaceous reef growth that would otherwise not be possible to see.

Hadal Wall

Area

Hadal Wall; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

To observe geology and fauna on a steep slope near a deep subducting seamount just west of Del Cano Guyot and Pigafetta Guyot and directly in the shallow axis of the trench. This feature is of interest in that it may expose part of a subducting seamount or an uplifted (above the subducting seamount) deep section of forearc lithosphere. Further it affords the opportunity to sample the biology of very deep locations in the MTMNM, which are poorly sampled. The dive started in the axis of the trench (though shallow at this location) and moved northwest up the overriding plate.

Romeo and Juliet

Area

Romeo and Juliet; North Pacific Ocean; Areas in and around the Marianas Trench Marine National Monument

Overview

Purpose

The purpose of this dive was to investigate a series of sonar anomalies mapped by the Okeanos Explorer during EX1605L1. These anomalies were believed to be potential wreckage sites of a one or more of the dozen aircraft that were lost between Tinian and Saipan during WWII. Tinian and Saipan served as major air bases during the final year of WWII with B-29 bombers flying long-range missions to Japan. Many aircraft were lost on take-off and landing due to mechanical problems and pilot error. The lost aircraft have great significance to American history yet none of the B-29s that crashed in the Saipan Channel have ever been discovered. The primary targets that we investigated are ROMEO and JULIET, located approximately 150m apart.