paleomagnetic evidence, both reversals and polar wandering data, was instrumental in verifying the theories of continental drift and plate tectonics in the 1960s and 1970s. some applications of paleomagnetic evidence to reconstruct histories of terranes have continued to arouse controversies. paleomagnetic evidence is also used in constraining possible ages for rocks and processes and in reconstructions of the deformational histories of parts of the crust.