They form when two tectonic plates are being pushed aside by the magma (liquid rock) rising from the asthenosphere. The magma rises through the crack and solidifies, forming new crust, and gets pushed aside by more magma, leading to the formation of mid-ocean ridges and underwater volcanoes. The movement of plates is a slow process, moving only about 2cm a year.
A famous example of a mid-ocean ridge is the mid-atlantic ridge, and is located along the floor of the atlantic ocean. Iceland is an island directly on the ridge, and was created by years of magma cooling at the surface.
A famous example of a mid-ocean ridge is the mid-atlantic ridge, and is located along the floor of the atlantic ocean. Iceland is an island directly on the ridge, and was created by years of magma cooling at the surface.