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.
Seafloor spreading occurs at a diversion boundary. At this point,  tectonic plates pull away from each other and the gaps fills with  magma from the mantle.   Divergent boundaries. Crust is destroyed at the convergent plate boundary. This is  usually between the oceanic and continental plates.