HYDROCELL is dedicated to investigate hydrothermal circulation at the Juan de Fuca Rigde, Northeast Pacific, off the coast of Canada. Cruise HYDROCELL II, SO111, 21 Aug. - 15 Sep. 1996 on board research vessel FS Sonne continuous a tradition of research cruises aiming at the geothermal investigation of conductive and convective processes at this young oceanic ridge.

Juan de Fuca Ridge is an extraordinary region for geothermal measurements, because high sedimentation on this young crust (0.5 - 5 Ma) allows good penetration and ideal measurement conditions. Determinations of heat flow along sediment basins of 100 - 200 m depth reveal an astonishing result: heat flow values reflect the buried crustal morphology. This leeds to the idea, that the upper oceanic crust (layer 2A) is isothermal. Horizontal fluid circulation is the most probable explanation for this effect.

The existence of hydrothermal circulation indicates that there should be areas of open flow in and out of the sediment. In fact, such areas can be identified at the edges of sedimentary basins and near bare rocks.

Correlated with pore water circulation is a fall out of minerals within pore space. In macro scale, this can be detected by refraction seismic velocity determinations. Several of these measurements have been carried out during this cruise to observe velocity variation with crustal age.