Paleomagnetic dating method
Geophysicists who specialize in paleomagnetism are called paleomagnetists.
Paleomagnetists led the revival of the continental drift hypothesis and its transformation into plate tectonics.
You may therefore be wondering why, if we have perfectly good dating methods already, we don't just use them.
However, the advantage of paleomagnetic dating is that we can use it on different rocks from those susceptible to our ordinary methods of absolute dating: while most radiometric methods usually require igneous rocks, paleomagnetism can be measured in sedimentary rocks.
In the 19th century studies of the direction of magnetization in rocks showed that some recent lavas were magnetized parallel to the Earth's magnetic field. Blackett provided a major impetus to paleomagnetism by inventing a sensitive astatic magnetometer in 1956.
Early in the 20th century, work by David, Brunhes and Mercanton showed that many rocks were magnetized antiparallel to the field. His intent was to test his theory that the geomagnetic field was related to the Earth's rotation, a theory that he ultimately rejected; but the astatic magnetometer became the basic tool of paleomagnetism and led to a revival of the theory of continental drift.
Paleomagnetism relied heavily on new developments in rock magnetism, which in turn has provided the foundation for new applications of magnetism.
These include biomagnetism, magnetic fabrics (used as strain indicators in rocks and soils), and environmental magnetism.
These curves diverged, but could be reconciled if it was assumed that the continents had been in contact up to 200 million years ago.Paleomagnetism is studied on a number of scales: The study of paleomagnetism is possible because iron-bearing minerals such as magnetite may record past directions of the Earth's magnetic field.