In 1968 the average salary of men teachers in maintained schools in England and Wales was Â£1,646. I estimate that the last two pay settlements have raised this figure to about Â£1,880. The comparable figure at 31st March, 1963, was Â£1,244.
Two main tectonic structures are spreading centers and subduction zones. Spreading centers occur at the boundary between two plates that are moving apart, called divergent plate boundaries. Here the plate motion opens a gap between the plates and magma from the mantle rises up through it.
Sea floor spreading is actually the creation of new oceanic  basaltic crust at divergent plate boundaries called mid-ocean  ridges. Material from the asthenosphere becomes m â¦ olten as  convection currents cause it to rise toward the thin upraised  boundary between plates there.ockhound. Spreading of seafloor occurs at the mid-ocean rifts, where there is a continuous flow of material rising from the mantle. There is not a unanimously accepted theory as to the cause of the rifting that is taking place.