Answer:
Seafloor spreading results from intense activity in the upper mantle which cracks the crust and pushes it away.
Explanation:
Seafloor spreading is a process that was first noticed by Alfred Wegener and was used by him in his theory of plate tectonics. There are three types of plate boundaries; convergent boundary, transform boundary, and divergent boundary. The last one is the one where seafloor spreading occurs.
The convection currents in the mantle are the process that breaks up the crust and move the tectonic plates, and when there is higher activity than usual at some place it results in break up the crust of an already existing tectonic plate. Basically, magma rises at a higher rate and pushes through the crust, in this case, the oceanic crust, and it manages to gradually break through it and come out on the seafloor. By doing so, the magma and the pressure from below are pushing the two now divided parts of the plate. As the space between the two different parts becomes larger and large the density of the crust becomes smaller and smaller so more and more magma rises through. The magma quickly solidifies on the ocean floor and piles up, thus creating an underwater mountain range known as a mid-ocean ridge.
