Sea Floor Magnetism

Looking at the magnetism of the seafloor scientists discovered something astonishing.

Sea floor magnetism.

But earth s magnetic field has reversed many times over the planet s history with the. In the mid 1960s evidence of magnetic stripes on the seafloor convinced the geologic community of the validity of plate tectonics theory and it is often pointed to today as clinching evidence for the theory. When seafloor lava solidifies at the seafloor its magnetic crystals are quenched in alignment with earth s magnetic field and the rocks magnetic polarity is preserved. As oceanic crust forms and spreads moving away from the ridge crest it pushes the continent away from the ridge axis.

Seafloor lavas have built in magnetic clocks that reveal their age. The field behaves as if a permanent magnet were located near the center of the earth. The magnetism of mid ocean ridges helped scientists first identify the process of seafloor spreading in the early 20th century. A test of the hypothesis of sea floor spreading was provided by studies of the earth s magnetism.

The earth s magnetic field the earth s magnetic field is thought to arise from the movement of liquid iron in the outer core as the planet rotates. Warships also carried magnetometers. Like the echo sounders the magnetometers were used to search for submarines. If the oceanic crust reaches a deep sea trench it sinks into the trench and is lost into the mantle.