Buoyant magma pushes up, driving plates apart. Cooler because it"s further away from the ridge. As the plate sinks, it pulls the rest of the plate behind it. Most heat source is at the mid ocean ridge. It"s cooler the further away it gets from the ridge. Most large earthquakes occur at subduction zones. Lithospheric plates interact with the neighboring plates in several ways. Eventually becomes a guyot because the tops are eroded down by the waves. Reefs continue to grow after volcanoes are submerged. Darwin developed the coral reef atoll development stages. As spreading continues, an ocean opens, passive margin cools and sediments accumulate. Convergence begins; an oceanic plate subducts, creating a volcanic chain at an active margin. Terrane accretions - from the sedimentary wedge welds material to the continent. As two continents collide, crust thickens and builds mountains. N and s america rifted from europe and africa.