Underhill is the name given to the area of very steep land, at the northern end of the

Isle of Portland The Isle of Portland is a tied island, long by wide, in the English Channel. The southern tip, Portland Bill, lies south of the resort of Weymouth, Dorset, Weymouth, forming the southernmost point of the county of Dorset, England. A barrier ...

Dorset Dorset ( ; Archaism, archaically: Dorsetshire , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by Somerset to the north-west, Wiltshire to the north and the north-east, Hampshire to the east, t ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

, which contains the villages of

Chiswell Chiswell , sometimes , is a small village at the southern end of Chesil Beach, in Underhill, on the Isle of Portland in Dorset. It is the oldest settlement on the island, having formerly been known as Chesilton. The small bay at Chiswell is ...

, Castletown and

Fortuneswell Fortuneswell is a village in Underhill, Dorset, Underhill on the Isle of Portland, in Dorset, England. It lies on steeply sloping land on the northern edge of the island, known as Underhill, where Chesil Beach connects the island to the mainland ...

. The remaining part of the island is known as

Tophill Tophill is a gently sloping area of land on the Isle of Portland in Dorset, England, rising from sea level at Portland Bill to near The Verne (HM Prison), HMP The Verne at its northern end. On Tophill are five of the Villages of Portland, set ...

. The geology of Underhill is different from Tophill; Underhill lies on a steep

escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. Due to the similarity, the term '' scarp'' may mistakenly be incorrectly used inte ...

composed of Portland Sand, lying above a thicker layer of

Kimmeridge Clay The Kimmeridge Clay is a sedimentary rock, sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation (geology), form ...

, which extends to

Chesil Beach Chesil Beach (also known as Chesil Bank) in Dorset, England, is one of three major shingle beach structures in Britain.A. P. Carr and M. W. L. Blackley, "Investigations Bearing on the Age and Development of Chesil Beach, Dorset, and the Associ ...

and

Portland Harbour Portland Harbour is beside the Isle of Portland, Dorset, on the south coast of England. Construction of the harbour began in 1849; when completed in 1872, its surface area made it the largest human-made harbour in the world, and it remains ...

. This Kimmeridge Clay has resulted in a series of landslides, forming West Weares and East Weares.

References

Isle of Portland {{Dorset-geo-stub