The Geology of Alstonefield is the geology of the Peak District which is the southernmost link of the Pennine Chain. Alstonefield lies on the extreme south of that chain, on an irregularly shaped limestone dome which is known as the White Peak. This is about 20 miles long from North to South, stretching from Castleton to Ashbourne and 12 miles wide from East to West stretching from Matlock to Buxton. The carboniferous limestones on which Alstonefield is situated are the oldest rocks exposed in the district and are enclosed by an irregular 'horseshoe' of gritstone open to the South.

The limestone was formed about 300 million years ago when the region was a shallow lagoon and Britain just south of the Equator. In the lagoon the skeletons of sea creatures were trapped in seaweed and the floor was a shifting mud of shells and skeletons. The currents swayed the fronds of Sea lilies or Crinoids until they died and their remains were then fossilised into the 'Derbyshire screws' seen on so many of the stones dug from gardens, turned up by farmers in their fields or casually placed in dry stone walls. Other shells were fossilised into the limestone and both limpet and cockle shells can often be identified.

Crinoids

Cockles

Some parts of the Peak District were in shallower waters then and their limestone consequently contains darker material due to the action of currents which usually flowed from the north and which deposited mud and silt as the gradient of the earth's surface changed. Limestone formed from deeper, clearer waters has a purer constitution and is laid down in horizontal layers. The chalky sediments could be up to 600 metres in depth.