Here's why:

* Divergent Boundaries: These are areas where tectonic plates move apart. As they pull away from each other, magma from the Earth's mantle rises to the surface.

* This magma cools and solidifies, creating new oceanic crust.

* This process is called seafloor spreading and is the primary way new crust is formed.

Example: The Mid-Atlantic Ridge is a divergent boundary where new oceanic crust is constantly being created.

Let me know if you'd like to know more about how crust formation occurs at divergent plate boundaries!