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.
Thus the mid-ocean ridge is also known as a spreading center or a divergent plate boundary.. The plates spread apart at rates of 1 cm to 20 cm per year. As oceanic plates move apart, rock melts and wells up from tens of kilometers deep.