SHEETED DIKES AND PILLOW LAVAS

-MAGMA IS INJECTED INTO CRACKS ABOVE THE MAGMA CHAMBER WHERE IT COOLS AND SOLIDIFIES TO FORM DIKES BETWEEN THE CHAMBER AND SURFACE

-COOLING DIKES ACQUIRE EARTH'S MAGNETIC FIELD AND SO YIELD THE MAGNETIC ANOMALIES THAT RECORD THE SPREADING HISTORY

-NEW DIKES INTRUDE BETWEEN OLD ONES, FORMING SHEETED DIKE SEQUENCE

-WHEN DIKES ERUPT AT THE SEAFLOOR, SEA WATER COOLS THE LAVA, FORMING ROUNDED PILLOW LAVAS