Here's why:

* Tundra formation: Tundras often form in areas where glaciers once existed. The glaciers scraped and eroded the land, leaving behind a lot of rock debris.

* Permafrost: Tundras are characterized by permafrost, a layer of permanently frozen ground. This frozen ground prevents the breakdown of rocks by weathering and erosion, leading to accumulations of rock fragments.

* Types of tundra: Different types of tundra, like Arctic tundra and alpine tundra, can have varying amounts of rock exposure. Alpine tundras, found on high mountaintops, are particularly known for their rocky landscapes.

So, while not all tundras are entirely rocky, you can definitely find plenty of rocks within these cold, harsh environments.