The hills are made up of rocks of middle and late Jurassic age with the hard Corallian Limestone forming the cap at the highest points. The highest point is Black Hambleton which rises to 1,308 feet (400 m) at the northern end of the range. Roulston Scar reaches 919 feet (280 m) and Whitestone cliff is 1,063 feet (324 m). The Corallian Limestone also outcrops along the southern edge of the North York Moors forming the Tabular Hills which run from Black Hambleton eastwards to Scarborough, although much broken through by river valleys.