Continental drift Permian era but failing to account for glaciation in India, Australia and South Africa. Geophysicist Jack Oliver is credited with providing seismologic evidence supporting plate tectonics which encompassed and superseded continental drift with the article "Seismology and the New Global Tectonics", published in 1968, using data collected from seismologic stations, including those he set up in the South Pacific. It is now known that there are two kinds of crust: continental crust and oceanic crust. Continental crust is inherently lighter and its composition is different from oceanic crust, but both kinds reside above a much deeper "plastic" mantle. Oceanic crust
Drift hypothesis at supported the drift hypothesis, but when he examined them, he found their conclusions were "based on assumptions and methods that lacked empirical support." Another statement in Fox's study was, in studies done on social class and mental illness, "identify drift as an individual's downward intergenerational social mobility after the onset of mental illness, rather than as residential drift from higher to lower class status areas". So depending on what one's definition of drift hypothesis is, there will be data either to support or refute the validity of it. From an economic perspective of social class and mental illness, the