The type of boundary where magma rises to the surface and new crust is formed is a divergent boundary.

Here's why:

* Divergent boundaries are where tectonic plates move apart. This creates space for magma from the Earth's mantle to rise up.

* As the magma cools and solidifies, it forms new crust, effectively pushing the plates further apart.

* This process is responsible for creating mid-ocean ridges, rift valleys, and volcanic islands.

Let me know if you'd like to learn more about divergent boundaries!