It stretches across the two ceremonial counties of Devon and Cornwall and the unitary authority area of Plymouth.

It contains fossils of plants and sea creatures and its cliffs show a timeline of the Middle to Early Devonian period hundreds of millions of years ago Lower to early Middle Devonian units of rock are visible from sections through the coastal cliffs and intertidal zones, which were laid down 417–354 million years ago.

[1] There are fossil remains of corals, brachiopods, bryozoa, gastropods, rare orthoconic nautiloids, ostracods, trilobites, phacopids), crinoids, ostracoderm and acanthodian fish.

[2] This is evidence a period of tectonic plate collision between 330 and 300 million years ago, which exerted pressure on the rock.

[2] The far south consists of red and green slates with sandstones that were deposited in rivers and lakes.