Weathering on Boulders at Chapmans Pool

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Many of the large boulders that have fallen from the crumbing cliffs down to the shores of Chapmans Pool in Dorset, England, show signs of being weathered by exposure to the elements. Over long periods of time, rain, sun, frost, chemical weathering from acid water and from biogenic elements,  mechanical weathering by wind-blown sand, and abrasion by wave-transported gravel and pebbles, have removed the surface of the rocks and revealed an amazing array of textures and patterns.

Softer rock matrices have been eroded to reveal harder structures normally hidden from sight within the boulders. These structures include networks of crystalline veins, as well as trace or ichno-fossils (where the hollows of burrows excavated by crustaceans in the sediments of ancient shores have been preserved, as the sediments were consolidated into rock, and eventually the spaces have been in-filled with harder and more resistant materials). It is interesting to see how small periwinkles frequently taken advantage of the dips and hollows of these eroding rocks to find shelter at low tide.

REFERENCES

Barton, C. M.; Woods, M. A.; Bristow, C. R.; Newell, A. J.; Westhead, R. K.; Evans, D. J.; Kirby, G. A.; Warrington, G. (2011) Geology of south Dorset and south-east Devon and its World Heritage Coast, Special Memoir for 1:50 000 geological sheets 328 Dorchester, 341/342 west Fleet and weymouth and 342/343 Swanage, and parts of sheets 326/340 Sidmouth, 327 Bridport, 329 Bournemouth and 339 Newton Abbot, Compiled by M. A. Woods, British Geological Survey, Keyworth, Nottingham.

Levin, H. L. (1990) Contemporary Physical Geology, Third Edition, Saunders College Publishing, Chapter 5: Weathering and Soils, pp 109 – 120 & 128, ISBN 0-03-031139-x.

Nichols, G. (2009) Sedimentology and Stratigraphy, Second Edition, Wiley-Blackwell, 6.4 Weathering Processes, pp 89 – 92, ISBN 978-1-4051-3592-4.

West, Ian M. 2013. Chapman’s Pool (Chapmans Pool), Houns-tout and Egmont Bight, Kimmeridge region, Dorset; Geology of the Wessex Coast (Jurassic Coast, World Heritage Site) of southern England. Internet site. http://www.southampton.ac.uk/~imw/Chapmans-Pool.htm. Ian M. West, Romsey, Hampshire. Version: 14th December 2013.

COPYRIGHT JESSICA WINDER 2014

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