Southern Hydrate Ridge

The Ocean Observatories Initiative (OOI) Regional Cabled Array (RCA), operational in the NE Pacific since 2014, includes a cabled junction box at Hydrate Ridge, a site of methane seeps at ~780m water depth approximately 90 km west of Newport, OR. Located in the central Cascadia accretionary complex, Hydrate Ridge is a well-known and highly studied gas hydrate deposit, with documented seafloor venting and formation of gas-rich hydrate deposits near the seafloor (Suess et al. 2002; Tryon et al. 2002). Previous research via drilling and remotely-operated vehicles (ROVs) provides a basis for understanding the heterogeneous distribution of gas hydrates in this area and the processes that lead to their formation (Trehu, et. al. 2004). Subseafloor imaging using three dimensional seismic surveys have defined a focused plumbing system that the OOI used to determine deployment locations for observatory sensors (Bangs, et al. 2011).

RCA infrastructure at Southern Hydrate Ridge as installed in 2019. Also shown are instruments funded by MARUM1 (2 sonars, 4K camera, and a CTD). Credit: University of Washington.

The digital still camera (CAMDSB103) sits atop a small, heavily sedimented rampart in front of the actively venting methane seep called Einstein’s Grotto at the summit of Southern Hydrate Ridge. Photo credit: NSF-OOI/UW/CSSF; Dive R1767; V14.

The fluid flow system at Hydrate Ridge appears to be controlled by structures that cut across stratigraphic horizons, which differs from gas hydrate systems explored on the northern Cascadia margin (Johnson, et al. 2003). There is also a greater abundance of coarse-grained sediments in the north (Trehu, et. al. 2004), which has a strong impact on gas hydrate deposition processes. The long-term OOI time series at Hydrate Ridge, coupled with data from central and northern Cascadia and other seep locations, will lead to a more comprehensive understanding of gas hydrate processes, changes over time, and the evolution of the biological community associated with these environments.

The OOI observatory includes seismometers, hydrophones, fluid samplers, seafloor cameras, and in situ chemical sensors (e.g., CH4, H2S); see table below for full list. Many of the key processes associated with gas hydrate systems occur over short time scales (e.g., gas hydrate release due to small and large earthquakes), so real-time data transmission and the capability for adaptive response and sampling adjustment are fundamental observatory benefits that bolster research advancements. The RCA infrastructure enables 24/7 real-time communications and power to the array of scientific instruments at Southern Hydrate Ridge.

Scarlet King Crabs were seen at multiple locations along Hydrate Ridge. They are often found in sandier substrate, however this one was sighted among a large group of brooding snails. Photo Credit: NSF-OOI/UW/CSSF; Dive 1758; V14

Southern Hydrate Ridge is a core component of the OOI because the science conducted at this site spans both seafloor and water column themes that form the foundation of the OOI: e.g., Climate Variability, Ocean Circulation, and Ecosystems; Coastal Ocean Dynamics and Ecosystems; Fluid-Rock Interactions and the Sub-seafloor Biosphere, and Plate-Scale Geodynamics. The cabled infrastructure at SHR specifically addresses 5 out of 10 OOI major science questions [as detailed in the Ocean Observatories Initiative (OOI) Scientific Objectives A Closer Look (2007), and as part of the Conceptual Network Design]. These include: 1) What is the ocean’s role in the global carbon cycle, and more specifically, gas hydrates and marine seeps? 2) How does plate-scale deformation mediate fluid flow, chemical and heat fluxes, and microbial productivity? 3) What are the forces acting on plates and plate boundaries that give rise to local and regional deformation and what is the relation between the localization of deformation and the physical structure of the coupled asthenosphere-lithosphere system? 4) How do tectonic, oceanographic, and biological processes modulate the flux of carbon into and out of the submarine gas hydrate ‘capacitor,” and are there dynamic feedbacks between the gas hydrate reservoir and other benthic, oceanic, and atmospheric processes? 5) What are the dynamics of hypoxia on continental shelves?


Bangs, N. L. B., Hornbach, M.J., and Berndt, C., 2011. The mechanics of intermittent methane venting at South Hydrate Ridge inferred from 4D seismic surveying. Earth and Planetary Science Letters. 310(1‐2): 105–112, doi:10.1016/j.epsl.2011.06.022.

Johnson, J.E., Goldfinger, C., Suess, E., 2003. Geophysical constraints on the surface distribution of authigenic carbonates across the Hydrate Ridge region, Cascadia margin. Marine Geology. 202(1–2): 79-120.

Suess, E., Bohrmann, G., Rickert, D., Kuhs, W.F., Torres, M.E., Trehu, A., Linke, P., 2002. Properties and fabric of near-surface methane hydrates at Hydrate Ridge, Cascadia margin. In 4th International Conference on Gas Hydrates (pp. 740 – 744), Yokohama, Japan.

Tréhu, A., Long, P.E., Torres, M.E., Bohrmann, G., Rack, F.R., Collett, T.S., Goldberg, D.S., Milkov, A.V., Riedel, M., Schultheiss, P., Bangs, N.L., Barr, S.R., Borowski, W.S., Claypool, G.E., Delwiche, M.E., Dickens, G.R., Gracia, E., Guerin, G., Holland, M., Johnson, J.E., Lee, Y.-J., Liu, C.-S., Su, X., Teichert, B., Tomaru, H., Vanneste, M., Watanabe, M., Weinberger, J.L., 2004. Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: constraints from ODP Leg 204. Earth and Planetary Science Letters. 222(3–4): 845-862.

Tryon, M., Brown, K.M., Torres, M.E., 2002. Fluid and chemical flux in and out of sediments hosting methane hydrate deposits on Hydrate Ridge, OR, II: hydrological processes. Earth and Planetary Science Letters. 201: 541–557.

Instruments at Hydrate Ridge

Instrument Name Make/ModelNumberScienceLife Cycle
Low Frequency HydrophoneHIT/90-U1T-waves, ocean acoustics, mammal detection5 Year
Broadband Ocean Bottom SeismometerGuralp/CMG-1T5T1Regional earthquakes5 Years
Short-period SeismometerGuralp/CMG-1 sec3Regional earthquakes, local cracking events, improve pumping system for methane gas subsurface5 years
Seafloor PressureSea-bird/SBE 541Tides, tsunami, storms, uplift, deflation5 years
3D Velocity MeterNobska/MAVS41Local currents3 years
ADCP 75 kHzTeledyne RDI/Workhorse LongRanger1Currents, bubble plume dynamics3 years
Digital Still CameraKongsberg/Custom1Bubble plume characterization, macrofauana and microbial distribution, seep morphology1 year
Benthic Flow MeterNon-commercial2Fluid flow into and out of the seafloor--flux calculations1 year
Osmo SamplerNon-commercial1Fluid chemistry, flux calculations1 year
Mass SpectrometerNon-commercial1Gas analyses, flux calculations1 year