As lava cools the minerals settle parallel to the earth s magnetic field.
Magnetic minerals on the ocean floor.
Magnetic striping of the sea floor after mid ocean ridges and trenches were discovered more evidence was discovered that helped to support the theory that the continents had moved around.
Evidence for seafloor spreading.
Magnetic reversalssome of the most important evidence of seafloor spreading comes from magnetic reversals recorded in the ocean floor.
Some igneous rocks contain minerals that are magnetic.
Throughout earth s history.
The figure below includes two images of the ocean floor.
From studies of the magnetic properties and the ages of igneous rocks on the ocean floor.
When magma flows out of a mid ocean ridge small magnetic minerals in the magma align themselves to point in the direction of the earth s current magnetic north.
Plate tectonics explains patterns observed in data from these studies.
They record the strength of the magnetic field in rocks on the ocean floor.
When the earth s magnetic field reverses a new stripe with the new polarity begins.
Plate tectonics and reversals of the earth s magnetic field are responsible for the magnetic stripes found on the ocean floor.
3 rocks containing iron give us a record of earth s magnetic field.
Basalt is one of these rocks.
Scientists can use this data to make magnetic maps of the ocean floor.
Such magnetic patterns led to recognition of the occurrence of sea floor spreading and they remain some of the strongest evidence for the theory of plate tectonics.
These two things were the magnetic striping on the ocean floor and the age of seafloor rocks.