Seafloor spreading occurs because
of plate tectonics. The Earth's lithosphere is divided into several rigid plates that float on the semi-fluid asthenosphere beneath them. These plates constantly move and interact with each other.
At mid-ocean ridges, divergent plate boundaries are formed where plates are moving away from each other. This movement creates a gap in the oceanic crust, and magma from the underlying mantle rises to fill the gap. This magma cools and solidifies, creating new oceanic crust.
As the new crust forms, it pushes the older, existing crust away from the ridge. This process is known as seafloor spreading. The spreading of these plates creates a continuous chain of mid-ocean ridges around the world, such as the Mid-Atlantic Ridge.
Over millions of years, the seafloor spreads and moves away from the ridge, making room for more magma to rise and create new crust. As a result, the oceanic crust gets younger and closer to the ridge, while the older crust moves away from the ridge and eventually subducts beneath another plate at a convergent boundary.
Seafloor spreading is a key process in plate tectonics and contributes to the continual renewal and reshaping of the Earth's crust. It also plays a significant role in the formation of new oceanic basins and the geological evolution of the planet.