Here's why:

* Divergent boundaries occur where tectonic plates move apart from each other.

* At the Mid-Atlantic Ridge, the North American and Eurasian plates are pulling apart, creating a gap.

* This gap allows magma from the Earth's mantle to rise and solidify, forming new oceanic crust.

* The process of new crust formation is called seafloor spreading, and it's the primary driver of the Mid-Atlantic Ridge's existence.

Let me know if you have any other questions about plate tectonics!