Deep ocean drilling and radiometric dating in the late 1960s gave an accurate stratigraphy and precise date of the ocean floor.
Therefore, seafloor dating isn't that useful for studying plate motions beyond the Cretaceous.For that, geologists date and study continental crust.The lone outlier (the bright splash of purple that you see north of Africa) to all of this is the Mediterranean Sea.The mid-ocean ridge is the region where new oceanic crust is created.The oceanic crust is composed of rocks that move away from the ridge as new crust is being formed.Seafloor spreading was proposed by an American geophysicist, Harry H. By the use of the sonar, Hess was able to map the ocean floor and discovered the mid-Atlantic ridge (mid-ocean ridge).
He also found out that the temperature near to the mid-Atlantic ridge was warmer than the surface away from it.
The seafloor was mapped by shipborne magnetometers in the 1950s and produced puzzling results - sequential zones of normal and reverse magnetic polarity spreading out from the oceanic ridges.
Later theories showed that that this was due to the reversing nature of Earth's magnetic field.
A younger oceanic crust is then formed, causing the spread of the ocean floor.
The new rock is dense but not as dense as the old rock that moves away from the ridge.
Every so often (it has occurred over 170 times over the past 100 million years), the poles will suddenly switch.