Figure 1. Mid-Atlantic Ridge emerges as the South American and African plates
pull apart at the "slow" rate of approximately 30 millimeters
per year. The axis of the ridge is marked by a 2 km deep rift valley, which
is typical of most slow-spreading ridges. The map reveals a 12 km jog of
the rift valley, a second-order discontinuity, and also shows a first-order
discontinuity called the Cox transform fault. Colors indicated depths of
from 1900 (pink) to 4200 meters (dark blue).