Solsbury Hill

Little Solsbury Hill was geologically formed from layers of sedimentary rock dating back to the Jurassic period. The plateau of the hill consists of Chalfield Oolite, underneath which lies Fuller's Earth, both part of the Bathonian (Middle Jurassic) Great Oolite Group. Below these layers, you find Bajocian Inferior Oolite limestone and Toarcian Bridport sandstone, followed by a thick layer of Charmouth Mudstone from the Lower Jurassic.

Top layer: The Chalfield Oolite formed the hard, erosion-resistant plateau of the hill, characteristic of the surrounding Cotswold plateaus.

Underlying formations: Lying on top of this are the Fuller's Earth (a clayey sediment layer) and further down are the limestone banks of the Inferior Oolite and sandstone of the Bridport Sand Formation.

Lowest layers: The Charmouth Mudstone forms the bedrock and extends beneath the river valley of the Avon.

Through millennia of erosion and river action, the current hill shape has emerged, where the relatively resistant oolitic limestone remained at the surface as a plateau while softer layers eroded away in the valleys.

The steep slopes and flat top are the result of differential erosion of the Bathonian limestone layers versus the underlying, softer sediments. Water and wind shaped the plateau and slopes.

All sides of the hill are susceptible to landslides, caused by the clayey underlayers and steep slopes.

The hill has been locally quarried (19th century), which partially influenced its geological profile.

Pascal Brackman