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.
Magnetic minerals on the ocean floor.
When the earth s magnetic field reverses a new stripe with the new polarity begins.
Evidence for seafloor spreading.
These minerals provide a record of the direction of earth s magnetic field at the time when the molten matter that formed the rock.
Magnetic striping magnetic minerals are found in rocks.
It is found in lava.
Basalt is one of these rocks.
3 rocks containing iron give us a record of earth s magnetic field.
As lava cools the minerals settle parallel to the earth s magnetic field.
These two things were the magnetic striping on the ocean floor and the age of seafloor rocks.
Plate tectonics explains patterns observed in data from these studies.
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.
Magnetic reversalssome of the most important evidence of seafloor spreading comes from magnetic reversals recorded in the ocean floor.
They record the strength of the magnetic field in rocks on 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.
Scientists can use this data to make magnetic maps of the ocean floor.