Deep-tow reflection data, seismic refraction data to ocean bottom seismometers, and gravity interpretations of the northern Juan du Fuca Ridge all suggest a very narrow or absent crustal magma chamber under this portion of the rise axis. The seismic features that have been suggested as indicating crustal magma chambers on other parts of the East Pacific Rise, such as travel time delays and reflections from the top of the shallow magma reservoir, are not found on the northern part of this ridge. These results indicate that at spreading rates of 3 cm/yr crustal cooling (probably by water penetration) is sufficiently rapid to prevent the existence of a steady state crustal magma chamber and therefore crustal accretion may be episodic.