Brimham Rocks - Geology

In the beginning...

320 million years ago, a huge river washed down grit and sand from granite mountains in northern Scotland and Norway. A delta formed, covering half of Yorkshire. Increasing layers of grit and sand, along with rock crystals of feldspar and quartz, built up to form the tough sandstone known as Millstone Grit, the exposed sections of which can be seen today at Brimham Rocks.

Cross-bedding

A feature of the rocks is their cross-bedding. As the water from the river flowed, it created bedforms such as ripples or dunes on the floor of the channel. Sediment was deposited on the downcurrent side of these bedforms at an angle - not horizontally. The layering is inclined and dips in the direction the water was moving.

Shaping

Most of the rocks owe their bizarre shapes to erosion during and after the Devensian glaciation. For example, Idol Rock was most likely formed just after the last glaciation when the land lacked any plant cover. Here, sand-blasting at ground level wore away the softer layers of the rock producing a tiny plinth with a massive top. Freeze-thaw action on the joints and bedding planes have shaped many of the tors such as the Dancing Bear.

the dancing bear

idol rock rock