Hydrate Ridge is a 25-km-long and 15-km-wide ridge located offshore Oregon (Fig. F1A) where Juan de Fuca plate obliquely subducts beneath North American plate (MacKay et al., 1992; MacKay, 1995; Goldfinger et al., 1997). Sediments in the vicinity of the ridge are composed of actively folded and faulted turbidites and hemipelagic sediments (Tréhu, Bohrmann, Rack, Torres, et al., 2003). Massive gas hydrates are observed near the seafloor and in the subsurface to a depth of ~50 meters below seafloor (mbsf) on the ridge summit, and pervasive bottom-simulating reflectors (BSRs) occur from the summit to the flanks and into the eastern slope basin of the ridge, indicating the presence of free gas underlying the subsurface gas hydrates in these sediments (Tréhu et al., 2004). Authigenic carbonates and chemosynthetic communities have also been observed at the southern peak of the ridge, where methane gas is discharged episodically into the overlying water (Torres et al., 2002; Suess et al., 1999; Heeschen et al., 2003).