Bathymetric data collected along the Mid-Atlantic ridge, between 20°N and 24°N, indicate a high variability of ridge morphology which is closely related to the 50 km wavelength segmentation recognized on this area. Each segment exhibits a particular morphology which indicates different stages of the ridge evolution and suggests asynchrony of the tectonic and magmatic history between two adjacent segments. Along a segment, the distribution and the width of volcanic and tectonic activities vary: these latter are much confined to the segment centres and widely scattered at either end. There is an abridged English version.