Seismic refraction on the Mid-Atlantic Ridge at 37°N

Two seismic refraction profiles were made on the mid-Atlantic ridge near 37°N. A median valley profile shows a low-velocity layer 3 (about 6.3 km/s) and a normal mantle velocity of 8.34 km/s. A second refraction line made on the western ridge flank (crustal age of 2 m.y.) shows a layer 3 velocity of 6.92 km/s and a completely developed layer 2B (5.24 km/s). A layer 2A velocity is observed both in the median valley and on the western flank.