Explain how ocean ridges and trenches are formed.

They are mid-ocean ridges, which form where two tectonic plates are spreading apart, which is called seafloor spreading. Tectonic plates are large pieces of the earth's crust, and they interact in a number of ways. Where they pull apart is called a divergent plate boundary.

When the tectonic plates in the Earth move away from each other they create trenches, ocean ridges are also formed by the Earths tectonic plates.