Here's a breakdown of why:

* Continental Caldera: A caldera is a large, volcanic crater formed by the collapse of a volcano after a massive eruption. Yellowstone's caldera is a result of several major eruptions over millions of years. It's located within the North American continental plate.

* Hotspot: Yellowstone sits atop a mantle plume, a column of abnormally hot rock rising from deep within the Earth's mantle. This hotspot provides the heat that drives the volcanic activity in the region.

Important Note: While Yellowstone is associated with a hotspot, it's not located at a plate boundary. Plate boundaries are where tectonic plates interact, causing earthquakes, volcanic activity, and mountain formation. Yellowstone is located in the middle of the North American plate, far from any major plate boundaries.