The dolorites at the quiver tree forest and giant's playground form part of the bigger sill complex. The dolorites are magma that was pressed up, but cooled off just below the earth's surface. The softer parts of the stone and the top layer of the earht's crust erodated away, which left the dolorites exposed.

The dolorites are between 160 and 180 million year old, and in the Keetmanshoop region cover an area of 180 000 km2.