Answer:
Step-by-step explanation:
The lithosphere (which includes the crust) is the outermost layer of the Earth and is cooler and more rigid than the layer below. The asthenosphere underneath is hot and flexible, transferring some of its heat through convection. In this case, the molten rock (magma) moves towards the cooler section, welling up through 100 km deep cracks in the lithosphere. When the two sides of the crack move apart, the cooled rock forms new tectonic plate material