Heat and fluid flux through sediment on the western flank of the Mid-Atlantic Ridge: A hydrogeological study of North Pond

A comprehensive survey of heat flow, sediment thickness and bathymetry in a large intermontane sediment pond on the western flank of the Mid‐Atlantic Ridge (North Pond) shows that only 20 to 25% of the heat escaping from the lithosphere flows through the sediments in the pond even though they completely cover a 70 km2 area of the seafloor. Three in situ pore‐pressure gradient measurements gave values that were negative relative to hydrostatic, indicating that there is drawdown of water through the sediment at rates of 1 to 5 mm/yr. North Pond is a recharge zone for hydrothermal circulation that is probably driven by lateral pressure gradients produced by topographic relief.