Three-dimensional diagram showing crustal generation and destruction according to the theory of plate tectonics; included are the three kinds of plate boundaries—divergent, convergent (or collision), and strike-slip (or transform).
The anomalies were charted from southern California to northern Washington and out several hundred kilometres.continental crust in several ways: it is thinner, denser, younger, and of different chemical composition.Like continental crust, however, oceanic crust is destroyed in subduction zones.They commonly form small hills tens of metres high at the spreading centres.Sheet flows have the appearance of wrinkled bed sheets.The lower gabbro layer has a stratified structure and evidently represents the floor or sides of the magma chamber.
This layered structure is called cumulate, meaning that the layers (which measure up to several metres thick) result from the sedimentation of minerals out of the liquid magma.
Bottom sampling during early exploration brought up all varieties of the above-mentioned rocks, but the structure of the crust and the abundance of the constituent rocks were unclear.
Simultaneously, seismic waves generated by explosions (such as dynamite blasts) set off over distances of several tens of kilometres.
A marine magnetic anomaly is a variation in strength of Earth’s magnetic field caused by magnetism in rocks of the ocean floor.
Marine magnetic anomalies typically represent 1 percent of the total geomagnetic field strength.
Russian-born American geophysicist Victor Vacquier noticed that these linear anomalies ended at the fracture zones mapped in this area.