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Gas hydrates are ice‐like solids that form in rigid cage structures under specific conditions of pressure, temperature, and gas and water concentration. Marine gas hydrates are stable in pore spaces of sediments in water depths greater than ∼300 m beneath the slopes of active and passive continental margins [Kvenvolden, 1988]. The lower limit of hydrate occurrence in marine sediments is determined by the geothermal gradient, so that the zone of hydrate stability is generally contained within the first few hundred meters of sediment. Continental hydrates occur in polar permafrost regions in the Arctic and Siberia. Most of the hydrates that have been discovered contain methane derived from microbial processes. Other hydrocarbons can also form hydrates, but in different structures of the surrounding water cages. Structure I, the most prevalent form, contains mostly (>99%) microbial methane, a small amount of ethane, and traces of C2+ hydrocarbons [Sassen et al, 2001]. Structure II and structure H hydrates contain significant quantities of thermogenic methane and larger, more complex hydrocarbons formed at high temperatures from fossil organic matter (i.e.,kerogen) or oil [Sassen and MacDonald, 1994].The gas origin is inferred from measurements of the carbon‐13 isotopic ratio (δ13); microbial methane is depleted in 13C (δ13 <−60‰) relative to thermogenic methane (δ13 from −20‰ to −50‰).

In metropolitan areas, PD and HHD generally increased with increased travel distance to the closest home dialysis facility and decreased with greater distance to an IHD facility. Examination of travel distances to PD and HHD facilities separately may provide further insight on specific barriers to these modalities which can serve as targets for future studies examining expansion of home dialysis utilization.

A transect of seafloor heat probe measurements on the Hikurangi Margin shows a significant increase of thermal gradients upslope of the updip limit of gas hydrate stability at the seafloor. We interpret these anomalously high thermal gradients as evidence for a fluid pulse leading to advective heat flux, while endothermic cooling from gas hydrate dissociation depresses temperatures in the hydrate stability field. Previous studies predict a seamount on the subducting Pacific Plate to cause significant overpressure beneath our study area, which may be the source of the fluid pulse. Double-bottom simulating reflections are present in our study area and likely caused by uplift based on gas hydrate phase boundary considerations, although we cannot exclude a thermogenic origin. We suggest that uplift may be associated with the leading edge of the subducting seamount. Our results provide further evidence for the transient nature of fluid expulsion in subduction zones.

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