Plates can be 50-250 miles thick. Sea levels also changes over time, exposing more or less crust. In divergence, magma from the mantle wells up in the opening between plates. This upward flow of molten material produces a continuous line of active volcanoes that spill out basalt onto the ocean floor. This is usually represented by an oceanic ridge.
Divergence can also develop within a continent, resulting in a rift valley.
In convergence, plates moving in opposite directions meet, and the result of the collision normally is a vast crumpling of the edges as one plate subducts under the other. These are destructive because they result in removal of part of the surface crust. In lateral slipping, two plates slip past one another laterally. The slippage edge is a great vertical fracture called a strike-slip fault. These boundaries usually form huge faults.