Diabase

We approach slowly, feeling the way this single stone reorganizes the little valley around its weight.

Dolerite formed when molten material entered the sedimentary sequence and cooled beneath the surface, crystallizing into a hard, dark rock.

The heat altered nearby shale, baking it and changing its texture along the contact.

Much later, erosion removed the overlying beds and exposed both intrusion and altered stone.

Erosion doesn't work alone on one rock while ignoring another.

It responds to the whole arrangement of hardness, fracture, slope, vegetation, and water.

Dolerite blocks break along joints, shale separates along bedding, and soil gathers wherever the resulting shapes permit.

The Karoo Shale Escarpment emerges from this relationship rather than from one material alone.