Present day - Coastal erosion especially in Holderness where the cliffs are receding 2 metres every year.

Ice Age - deposition of Boulder Clay and gravels by huge glaciers. Ended about 12 000 years ago, started about 2 million years ago (2 ma).

Tertiary (started 65 ma ago)- uplift, folding, faulting and erosion, no rocks deposited. Intrusion of the Cleveland Dyke about 58 ma ago.

Late Cretaceous - deposition of 400 metres of Chalk - a white limestone containing fossil Inoceramus bivalves, sea urchins and belemnites. It formed in a huge shallow shelf sea. Thin deposit of Red Chalk at base. about 100 ma to about 70 ma.

[Short gap]

Early Cretaceous - deposition of the Speeton Clay - grey marine clays containing belemnites, oysters, ammonites and 'shrimps'. 144 ma to about 115 ma

[Short gap]

Late Jurassic - deposition of the Ancholme Clay - dark grey marine clays and shales containing ammonites, bivalves and belemnites. 163 ma to about 150 ma.

Middle Jurassic - a variety of rocks deposited in different environments. Limestones in shallow marine lagoons and sandstone in rivers and deltas. Fossilised plants, trees and dinosaur footprints found in the sandstones. 188 to 163 ma.

Lower Jurassic - grey mudstones and shales, containing ammonites, belemnites and the oyster Gryphaea. 213 ma to 188 ma.

Triassic - red clays formed in desert-like conditions. Usually not exposed.

Earlier rocks are beneath these but are not exposed.

Notes - the dates given are approximate and are for the Yorkshire rocks not the whole span of the time periods. This is intended only as a brief introduction to the geology of the area.