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 Simplified cross section through the Black Down area. Modified from Farrant, A.R. 2008

The geology of the area is dramatic and varied and is what defines both the landscape and the wide variety of habitats that are found here. The northern part of Burrington Ham and Burrington Combe, are formed by a series of Carboniferous Limestone beds which dip almost vertically due to the folding of the rocks. As limestone is porous there is no surface water and below ground there are a series of complex cave systems that have formed by the eroding water widening joints and cracks in the rocks.

The underlying geology of Black Down, to the south of Burrington Combe, is different as it is composed of Old Red Sandstone found at the heart of the anticline. The younger more permeable rocks have eroded away leaving the more resistant harder rocks exposed and forming the highest point in the Mendip Hills (325m). For more information on the geology of Black Down, download the factsheet from the resource centre.

Caring for Black Down

The project is raising awareness of the importance of the site for geology. If you see fossils in the rocks please leave them where they are for everyone to view.

Things to do

Why not try and find where the different rock types meet up. Walk up from the top car park in Burrington Combe onto Black down via the Ellick House path. As you climb up the hill keep an eye on the colour of the rocks under your feet and see if you can see where the grey stones of the limestone beds turn into the reddish tones of the Old Red Sandstone. Also where you have rock outcrops on Black Down look for evidence of ripple marks and cross bedding formed by the ancient river system that deposited the sandstone 360 million years ago.