The magnificent range of hills that marks the northwestern boundary of the National Park is also a major geological boundary.
The great slab of Middle Jurassic rock that forms the central moorland rises up gradually to the north and west of Eskdale. These rocks were formed in deltas and sandbars and contain fossil plants and dinosaur footprints.
The hard gritty rocks of the moorland are being worn away from the north and west by springs, rain and rivers. And because the Lower Jurassic rocks beneath them are relatively soft, a steep escarpment is formed along this eroding edge. The result is a range of hills with a gradual slope to the south and a steep drop to the north and west, down into the flood plain of the River Tees.
A major exception to this pattern is the most famous of the Cleveland Hills.
Roseberry Topping is what is known as an outlier. Erosion has cut the hill off from its geological relations, and a small remaining slab of hard Middle Jurassic sandstone on its summit is responsible for its existence. This beautiful landscape feature is a real example of defiance in the face of the elements.