The Real Jurassic Park: Geological Explorations in Southwest England
University of Washington, Tacoma
TESC 417: Summer 2006
The Real Jurassic Park: Geology field course along the south coast of England (TESC 417)


Location: Chesil Beach

July 31, 2006--Chesil Beach is known as one of the finest tombolo beaches in the world. The views from the Isle of Portland were astounding. We gathered on the hill overlooking the narrow strip of land connecting the Isle of Portland to the mainland and Chesil Beach and could see for miles. We walked along Chesil Beach fighting extremely high winds from the southwest and were amazed to see the endless supply of pebbles. Although it was tempting to take a few in our pockets, we refrained from doing so as it was not allowed and we all wanted a good grade more than than a souvenir! (Brunsden, 42-43)

Detail Map:

The Saxon word for pebble is chesil, and it is very appropriately named--Chesil Beach was a never-ending isle of pebbles, as far as we could see. The beach is over 17 miles long and the pebbles increase in size as you move eastward. The smallest sized pebbles are at West Bay and are the size of peas; as you go east at Portland, they are about the size of potatos. The pebbles are moved eastward by the action of the waves and wind. (Brunsden, 42) It used to be that when fishermen landed on the bank at night, they could judge their position by the size of the pebbles. (West, Chesil Beach)

The beach is connected to Portland at Chiswell. To the northeast is Portland Harbor, and Fleet lagoon is to the northwest.

Class discussion turns windy--overlooking Chesil Beach

Synopsis of Area:
Although there is some debate on how the beach was formed, it is generally agreed that it was formed by rising sea levels. A plaque at Chesil Beach gave this explanation: Chesil Beach was formed in the Holocene age which was approximately 6,000 years ago. It was formed by rising sea levels and it now protects the lowlands of Weymouth and the Fleet which is considered one of the most important lagoons in Europe. It is one of the finest barrier beaches in the world. The beach is over 17 miles long and the stones and pebbles increase in size as you move eastward. They are pea-sized at West Bay, and at Portland, they are the size of a potato.

Longshore drift and the forming of Chesil Beach: Approximately 125,000 years ago, the sea levels were higher than they are today and landslides of East Devon and West Dorset were active. Then, during the Ice Age, sea levels dropped. The cliffs along this coastline decayed into large debris slopes that spilled across the exposed sea floor. When the Ice Age ended, the rising sea levels reached these large landslides and released vast amounts of chert and flint into the shoreline. Longshore drift then carried the pebbles eastward and covered the beach that was brought in by the rising sea. The beach is still moving on shore. (Jurassic Coast)

The pebbles that you find in great quantities at Chesil Beach are made up of resistant quartz. This grey-brown flint comes from Cretaceous chalk and the light blue-grey chert comes from the Upper Greensand. At the far east end there is some black chert. The pebbles are as hard as steel and extremely difficult to scratch. The color depends on the iron content, as well as its state of oxidation. (West, Chesil Beach)

Large pebbles on the east end of Chesil Beach

Small pebbles in West Bay on the western end of Chesil Beach

It was Monday, July 31st, and day five in the field. We spent the morning learning about economic geology and building. We spent the afternoon learning about coastal geohazards and coastal geomorphology/processes at Chesil Beach. We toured the visitor's center and were now ready to depart for our new destination, Lyme Regis. Piling into the van, our caravan headed for new territory down A354 to Dorchester and our new home, Woodberry Down.

Stella takes her dad for a walk on the beach

Links to Related Projects:
The Cretaceous Chalk in Southern England. By Brieanna Graham
Geology and Tourism on the South England Coast. By Jenny Ripatti
Holy Architecture!: Cathedrals, Abbeys, and Parish Churches of Southwest England. By Lisa Green
World Heritage: Conservation Efforts in the United Kingdom and Ireland. By Jeanine Riss
Geology, Landscapes, and Land Use of Dorset and East Devon. By Angus Leger

Other Related Links:
Geology of the Wessex Coast, Southern England by Ian West

References and Acknowledgements:
-- Brunsden, Denys. The Official Guide to the Jurassic Coast, Dorset and East Devon Cost World Heritage Site. Coastal Publishing. Wareham, England, 2003.
-- Dorset: Coast and Countryside, Historic Towns and Villages. J. Salmon, Sevenoaks, Kent, 2006.
-- Detail Map: 2006 September 2, 2006.
-- Dorset County Council (2006). Jurassic Coast. September 22, 2006.
-- West, Ian (2005) Chesil Beach - Pebbles. September 9, 2006.