Explain how ocean ridges and trenches are formed.

Answer:

The upwelling of magma from the asthenosphere pushes on thin regions of oceanic crust, causing them to thicken and move upward, forming ridges. Gravity and slab pull in the Earth’s tectonic plates then pull down on the ridge and the material in the ridge spreads out across the ocean floor. When slab pull drags one edge of a tectonic plate under another it creates an oceanic trench.