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Jack Oliver is credited with providing seismologic evidence supporting plate tectonics which encompassed and superseded continental drift with the article "Seismology and the New Global Tectonics", published in 1968, using data collected from seismologic stations, including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
Continental Divide of the Americas such as the International Hydrographic Organization add a sixth: Canada's Northwest Passage basin. Using just the five, there are four secondary continental divides and three secondary triple points, the two mentioned previously and a third near Hibbing, Minnesota, where the Northern Divide intersects the Saint Lawrence Seaway divide. Since there is no true consensus on what a continental divide is, there is no real agreement on where the secondary triple points are located. However, the main Continental Divide described in this article is a far more distinctive geological feature than the others and its two main triple points are much