Final answer:
When plates move away from each other, they form a divergent boundary, characterized by the creation of new crust as magma rises to fill the space created by the separating plates.
Step-by-step explanation:
Types of Plate Boundaries
When plates move away from each other, they form a type of boundary known as a divergent boundary. At these boundaries, the lithospheric plates are pulling apart from one another, often creating rift zones such as the Mid-Atlantic Ridge. The space created by this separation allows molten rock, or magma, to rise from the asthenosphere to fill the gap, leading to volcanic activity and the formation of new crust. This process can generate features like mid-ocean ridges and can even lead to the development of new ocean basins. Apart from divergent boundaries, there are also convergent and transform boundaries. Convergent boundaries occur where plates move toward each other, possibly leading to subduction zones and mountain belts. Transform boundaries occur where plates slide past each other, leading to earthquakes along faults but typically no volcanic activity.