Model for the Formation of Topographic Features of the East Pacific Rise Crest

The topography of the East Pacific Rise axis is characterized by a central axial block 300 to 400 m high and 15 to 20 km wide. The axial block is flanked by asymmetrical abyssal hills tilted so that their steep slopes face the axis. Extrusion of basalt along the spreading center forms the axial block. According to the proposed model, subsidiary peaks or shoulders of the axial block are formed by faulting along surfaces that dip steeply toward the axis at the surface but decrease in dip with increasing depth. As the shoulders of the axial block are moved laterally outward by the spreading process, they are lowered along the curving fault surfaces to form the observed tilted abyssal hills.