The area where one of the huge plates under Earth's surface slides or pulls away from the edge of another plate, allowing magma to rise to the surface, is called a divergent plate boundary.

Here's a breakdown:

* Divergent Plate Boundary: This is where tectonic plates move apart from each other.

* Magma Rising: As the plates move apart, the gap created allows magma from the Earth's mantle to rise to the surface.

* Volcanic Activity: The rising magma often erupts, leading to volcanic activity and the formation of new crust.

Examples:

* Mid-Ocean Ridges: These underwater mountain ranges are formed along divergent plate boundaries. The mid-Atlantic Ridge is a well-known example.

* Rift Valleys: These are areas on land where the crust is being pulled apart. The East African Rift Valley is a prominent example.

Let me know if you have any other questions about tectonic plates or Earth's surface!