Sea Floor Magnetism

The magnetism of mid ocean ridges helped scientists first identify the process of seafloor spreading in the early 20th century.

Sea floor magnetism.

Basalt the once molten rock that makes up most new oceanic crust is a fairly magnetic substance and scientists began using magnetometers to measure the magnetism of the ocean floor in the 1950s what they discovered was that the magnetism of the ocean floor around. Seafloor lavas have built in magnetic clocks that reveal their age. But earth s magnetic field has reversed many times over the planet s history with the. 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.

The magnetometers also revealed a lot about the magnetic properties of the seafloor. As oceanic crust forms and spreads moving away from the ridge crest it pushes the continent away from the ridge axis. If the oceanic crust reaches a deep sea trench it sinks into the trench and is lost into the mantle. Like the echo sounders the magnetometers were used to search for submarines.

The magnetic stripes continue across the seafloor. 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. A test of the hypothesis of sea floor spreading was provided by studies of the earth s magnetism. 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.