Laboratory 2 Tectonism - large-scale movements and deformation of Earths crust. Continental Drift Hypothesis – Alfred Wegener’s hypothesis that all continents were once part of a single supercontinent, Pangea. Shrinking Earth Hypothesis – “anti-drift” scientists suggested that earth was cooling from an older semi-molten state, so it must be shrinking, also suggested that the continents were moving together. Expanding Earth Hypothesis – suggested that earth was once much smaller and covered entirely by granitic crust. As Earth expanded, the granitic crust split apart into the shapes of the modern continents and basaltic ocean crust was exposed between them. Plate Tectonics Hypothesis – suggested that the continents are parts of rigid lithospheric plates that move about relative to one another. Divergent Boundaries – where plates form and spread apart, such as mid-ocean ridges, where magma rises up between two plates forces them to spread apart and cools to form new rock on the edges of both plates. Convergent Boundaries –
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