Dancing Ledge - Langton Matravers, Dorset
Posted by: Groundspeak Premium Member SMacB
N 50° 35.530 W 002° 00.342
30U E 570378 N 5604946
Dancing Ledge is so called because at certain stages of the tide when the waves wash over the horizontal surface, the surface undulations cause the water to bob about making the ledge appear to dance.
Waymark Code: WMNNMM
Location: Southern England, United Kingdom
Date Posted: 04/09/2015
Published By:Groundspeak Premium Member veritas vita
Views: 2

"In the eastern part of Jurassic Coast World Heritage Site, Dancing Ledge is a notable feature. This is a large gently sloping ledge of part of the Portland Cherty Series, with a large abandoned quarry above. It has been said to have received its name from the appearance waves "dancing" on the ledge (although this is not particularly noticable) or because the sea ledge was humourously suggested to be as big and flat (but not smooth) as a dance floor ( Bruce, 1989). Actually there seems to have been dancing on the ledge with the help of a brass band. The brass band certainly played, as the author who mentioned this was a member of the band () Hardy (1910). This is odd because a worse place for dancing, i.e. on the uncomfortable Prickle Bed, could hardly be chosen. The name "Dancing Ledge" was probably in use long before the brass band entertainment. Although there is no specific evidence for this, it may be more probable that the name is some corruption of a reference to the springs which lead to water trickling over the cliff near here. Immediately to the west of adjacent Green Point. The wet, slimy cliff is unusually dark - thus - "Dark Spring Ledge" was probably the original name.

In addition to this present water flow, at one time some fresh water may have trickled seaward at this very locality, rather than just to the east of it. As mentioned below there is a vertical pothole, a small vadose zone cave feature that is obviously the result of downward flow of water from the Purbeck clays above (perched aquifer) down through the Portland Stone.

The upper, quarried ledge has some adits or galleries, mostly (but not all) now partly closed, and some old piles of quarry debris with some fossils. The area is used for the training of rock climbers. A bathing pool has been quarried out of the lower ledge for Durnford Preparatory School.

The quarry, cliffs and ledge here provide a good section through the upper part of the Portland Cherty Series and through the Portland Freestone. Fallen blocks of stromatolitic limestone come from the basal Purbeck Formation above. Ammonites can be seen, various features of silicification are clear, sponge spicules can be seen in the chert, bivalves in the Portland Freestone are common. There is a small karstic cave and interesting travertine features. Cave development by the sea can be studied. To the east of Dancing Ledge is a significant fault affecting the cliffs and the topography just inland. A dry valley with hillwash deposits descends to the quarry, and the topic of former water flow in the area is of interest. Jointing in the Portland Stone is also interesting.

The quarry is very old and is peculiar in that it is probably the largest cliff quarry in Dorset without any road access. The limestone quarry provided good building stone from the Under Freestone Bed only of the Portland Limestone Formation and in addition various rock for sea walls, particularly at Ramsgate. This work took place a long time ago and the quarrying was finished and the place much as it now by mid Victorian times.

Seaward and lower than the old working quarry is a a large natural sea ledge, an original promontory formed by the Prickle Bed, J', of the Portland Chert Member of the Portland Stone Formation. The Prickle Bed dips to the east and descends below sea-level (which rarely happens elsewhere). Now the Prickle Bed is notable for being the most bioturbated, crab-burrowed part of the Portland Chert Member. As a result it is non-uniform and connected by linking burrows. Because of the near-randomness of the burrow system the cementation has been extremely irregular. Thus the rock does not behave in a uniform manner and it only has joint at wide spaced intervals; it is not prone to close jointing. Thus the bed is thin but strong and relatively resistant to wave action. Dipping into the sea it forms a "Hard", a landing area for boats. There is a similar situation on a smaller scale at the cliff quarry of Kimmeridge oil shale at Clavell's Hard. That quarry and set of mines, like the quarry and mines of Dancing Ledge has no road connection. Perhaps both Clavell's Hard and Dancing Ledge represent sites of early quarrying for sea transport before many roads reached the coast in this region.

When the quarry was abandoned it became a place for smuggling and for visiting, swimming and othjer recreation. Rock climbing there has been a more recent development."

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