Portland Raised Beach

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File:Portland Raised Beach, Portland Bill.JPG
The Pleistocene Raised Beach.
File:Portland Bill Raised Beach, Dorset.JPG
Part of the Pleistocene Raised Beach inside the Ministry of Defence Magnetic Range.

Portland Raised Beach (the west Pleistocene Raised Beach) is a raised beach, located at Portland Bill, on the Isle of Portland, Dorset, England; and is part of the Jurassic Coast. There are two major raised beaches located at Portland Bill, although the Pleistocene Raised Beach is often considered to be the more widely noted beach of the two.

The two raised beaches (sometimes labelled as the west and east raised beaches) at Portland Bill represent the significant changes fluctuations in sea level and climate change during the last Ice Age, and both largely consist of shelly and sandy pebble deposits.[1][2] The cause of the two fluctuations was twofold: the growth of the ice, which absorbed large quantities of water, and the weight of the ice in the north that caused the landmass to tilt.[3]

Background

Portland Raised Beach

The west Pleistocene Raised Beach is found close to Portland Bill Lighthouse and Pulpit Rock, and is situated next to the Ministry of Defence Magnetic Range, where part of the beach is located behind fencing. This lies in a shallow embayment known as White Hole. Considered an important feature in the area, the Pleistocene Raised Beach dates from a warm interglacial phase of the Pleistocene ice ages, approximately 200,000 years ago.[4][5]

The beach is on private land, as is the surrounding ex-quarried land next to the beach, although the public are allowed beyond the warning sign at their own risk. Interference with the deposits of the beach remain prohibited.[4]

Second Raised Beach

The second east raised beach is located near Cave Hole and the beach huts. The beach deposits are on a slope, with a stone ledge below. An old crane stands on the beach.[6] The beach is about 125,000 years old and has abundant mollusc shells such as species of Patella and Littorina and small bivalves that lived on seaweed. It has been much disturbed by cryoturbation (freezing and thawing) during the late Pleistocene ice age. Unlike the older Pleistocene Raised Beach further east no human remains have yet been found here.[1]

References

  1. 1.0 1.1 "Portland Bill - Geological Field Guide". Southampton.ac.uk. 2012-10-19. Retrieved 2013-07-12.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. "Quick facts about the Jurassic Coast". Jurassiccoastline.com. Retrieved 2013-07-12.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  3. Paul, Ensom (1998). Discover Dorset: Geology. Wimborne: Dovecote Press. p. 78. ISBN 1 874336 52 0.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  4. 4.0 4.1 "File:Portland Raised Beach, Portland Bill, Dorset.JPG - Wikimedia Commons". Commons.wikimedia.org. 2013-07-07. Retrieved 2013-07-12.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  5. "Portland Bill, Portland, Dorset". Geoffkirby.co.uk. Retrieved 2015-01-26.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  6. "Portland Bill". Heightshotel.com. Retrieved 2013-07-12.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

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