Here's why:

* Divergent Plate Boundaries: These boundaries are where tectonic plates move apart from each other.

* Mid-Atlantic Ridge: This is a major undersea mountain range that runs down the middle of the Atlantic Ocean. It is where the North American and Eurasian plates are slowly pulling apart.

How it impacts Thingvellir:

* Rift Valley: Thingvellir is located within a rift valley formed by the separation of the plates. This valley is filled with spectacular canyons, fissures, and waterfalls.

* Volcanic Activity: The separation of the plates allows magma from the Earth's mantle to rise, resulting in volcanic activity. This has created many of the park's distinctive geological features.

* Earthquake Activity: The movement of the plates also causes earthquakes, making Thingvellir a geologically active area.

The unique combination of geological features makes Thingvellir National Park a fascinating and important location for studying plate tectonics.