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Jack Oliver is credited with providing seismologic evidence supporting plate tectonics which encompassed and superseded continental drift with the article "Seismology and the New Global Tectonics", published in 1968, using data collected from seismologic stations, including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 Drift hypothesis Drift hypothesis, concerning the relationship between mental illness and social class, is the argument that illness causes one to have a downward shift in social class. The circumstances of one's social class do not cause the onset of a mental disorder, but rather, an individual's deteriorating mental health occurs first, resulting in low social class attainment. The drift hypothesis is the opposing theory of the social causation thesis, which says being in a lower social class is a contributor to the development of a mental illness. A study by E. M. Goldberg and S. L. Morrison looked at