EXchange between Crust and Ocean means to observe exchange of material and energy at the flanks of oceanic ridges The target of marine expeditions EXCO I (SO105, 8 Nov -30 Dec 1995) and EXCO II (SO145, 21 Dec 99 - 28 Jan 00) onboard RV Sonne was the "superfast" spreading East Pacific Rise at 14° S.

The change of young oceanic crust (0 - 9,5 Ma) due to alteration within pore space and increasing sediment coverage has consequences for seismic velocity of the upper crust (layer 2A), ocean depth, roughness of seafloor, and dissipated heat.

Reconnaissance surveys of refraction seismic velocity and heat flow indicate a rapid cooling and adaption of the young crust to a stable equilibrium within the first 8 Ma. Detailed investigations reveal that apparently small disturbances like seamounts provide a significant contribution to the thermal equalization.