Seafloor spreading is just one part of plate tectonics. At subduction zones, the edge of the denser plate subducts, or slides, beneath the less-dense one. The denser lithospheric material then melts back into the Earth’s mantle. Seafloor spreading creates new crust.

Seafloor spreading helps explain continental drift in the theory of plate tectonics. Plates that are not subducting are driven by gravity sliding off the elevated mid-ocean ridges a process called ridge push. At a spreading center, basaltic magma rises up the fractures and cools on the ocean floor to form new seabed.

Slab pull is the pulling force exerted by a cold, dense oceanic plate plunging into the mantle due to its own weight. The theory is that because the oceanic plate is denser than the hotter mantle beneath it, this contrast in density causes the plate to sink into the mantle.

The main driving force of plate tectonics is gravity. If a plate with oceanic lithosphere meets another plate, the dense oceanic lithosphere dives beneath the other plate and sinks into the mantle. This process is called subduction.

The forces that drive Plate Tectonics include:

• Convection in the Mantle (heat driven)
• Ridge push (gravitational force at the spreading ridges)
• Slab pull (gravitational force in subduction zones)

Slab pull is that part of the motion of a tectonic plate caused by its subduction. Plate motion is partly driven by the weight of cold, dense plates sinking into the mantle at oceanic trenches. This force and slab suction account for almost all of the force driving plate tectonics.

The motion of tectonic plates is driven by convection in the mantle. There are three main forces that determine the rate at which tectonic plates move as part of the mantle convection system: slab pull: the force due to the weight of the cold, dense sinking tectonic plate.

Seafloor spreading

The main features of plate tectonics are: Convection currents beneath the plates move the crustal plates in different directions. The source of heat driving the convection currents is radioactivity deep in the Earths mantle.

The force that causes most of the plate movement is thermal convection, where heat from the Earth’s interior causes currents of hot rising magma and cooler sinking magma to flow, moving the plates of the crust along with them.