[4] Lias contains clays highly prone to expansion and contraction which aid landslip and collapse, therefore helping to facilitating the release of accessible fossils.

The Lilstock and Westbury formations, containing shale, limestone and sandstone, are included in the parent Penarth Group and they were deposited in the Rhaetian Age (208.5 to 201.3 mya) of the Triassic Period.

The next layer down is made up of the pale greenish- or bluish-grey mudstones and siltstones of the Blue Anchor Formation which, at the boundary, can share some of the same features with the overlying Westbury rocks.

The fossils to be found on the foreshore are largely from the beds of Blue Lias, Lilstone and Westbury formations from the top of the cliff and reflect the marine nature of the deposits.

This material, when sifted through, is an excellent source of tiny crinoid fossils, with the familiar sorting in this location into tubes and star-shaped segments - sometimes in stacks of several at a time - and can be easily found by the keen eyes of children or by using a hand lens.