The questions to answer.
1. How many entrances are there leading into the Gin cave (Granted you may have to crawl)?
2. Provide an estimate of the length, width and height at the centre of the main cave?
3, Was it a fault or a dike or a crack in the bedding planes that gave access to the sea to begin the formation of the caves
4. What action has formed the cave and what is present that would assist the sea in enlarging the cave.
5. Based on the sequence in the diagram (below), which picture(s) best represents the coastline at the coordinates and what will be the next stage.
6. Please attach a photo to your log of you, your dog, gps, calling card to prove you were here. Please do not show any spoilers in your photo and do not send us the photo. Post it with your log!
Black Hall Rocks contains some of the largest cave formations to be found on the Durham coastline, the magnesian limestone cliffs here measure 15–32m in height. The Gin Cave is an example of a Sea (Littoral) Cave. To the east of County Durham sits a plateau of Magnesian Limestone which slopes gently towards the North Sea. This limestone formed during the Permian age. The magnesian limestone is so called due to the high magnesium content derived from the presence of dolomite (Calcium Magnesium Carbonate). The Permian period, which occurred around 250 to 290 million years ago. Back then, the Durham coast resembled the Great Barrier Reef in Australia, with tropical reefs stretching along it. The rocks at Blackhall are famous for their Permian Magnesian limestone outcrops, revealing the story of this ancient time. There are several bedding formations along these cliffs, they are the Ford Formation, the Roker Formation, and the Seaham Formation. There are several bedding planes / formations in close proximity here. Close to the Gin cave these formations are reversed to what they are further up the coast.
A sea cave, also known as a littoral cave, is a type of cave formed primarily by destructive wave action. The primary process involved is erosion. Sea caves are found throughout the world, Littoral caves may be found in a wide variety of host rocks, ranging from sedimentary to metamorphic to igneous, but caves in the latter tend to be larger due to the greater strength of the host rock.
In order to form a sea cave, the host rock must first contain a weak zone. In metamorphic or igneous rock, this is typically either a fault or a dike. In sedimentary rocks, this may be a bedding-plane parting or a contact between layers of different hardness. The latter may also occur in igneous rocks.
The driving force in littoral cave development is wave action. Erosion is ongoing anywhere that waves batter rocky coasts, but where sea cliffs contain zones of weakness, rock is removed at a greater rate along these zones. As the sea reaches into the fissures thus formed, they begin to widen and deepen due to the tremendous force exerted within a confined space, not only by direct action of the surf and any rock particles that it bears, but also by compression of air within. Blowholes (partially submerged caves that eject large sprays of sea water as waves retreat and allow rapid re-expansion of air compressed within) attest to this process. Adding to the hydraulic power of the waves is the abrasive force of suspended sand and rock. Most sea-cave walls are irregular and chunky, reflecting an erosional process where the rock is fractured piece by piece. However, some caves have portions where the walls are rounded and smoothed, typically floored with cobbles, and result from the swirling motion of these cobbles in the surf zone.
True littoral caves should not be confused with inland caves that have been intersected and revealed when a sea cliff line is eroded back, or with dissolutional voids formed in the littoral zone on tropical islands. Life within sea caves may assist in their enlargement as well. For example, sea urchins drill their way into the rock, and over successive generations may remove considerable bedrock from the floors and lower walls.
Access to this earthcache is by the beach at low tide. This is obviously tidal, DO NOT attempt any access on an incoming tide as you are likely to be cut off and currents are strong. Please be aware that tides can come in quickly especially in the winter months so please refer to local tide times as published and keep an eye on the sea! The sea enters the cave at high tide.
Any photos of the gin cave taken from the cliffs will not be accepted. The cliffs are not fenced and visitors should not stray from the paths.
Access and Parking
Parking is free and there is plenty of it at N54 44.481 W1 16.166.
Access to the beach is located at N54 44.759 W1 16.286 via a concrete slope!
The walk from the car park is approximately 550m then there are some very steep slope down to the beach. You will then have a walk along the beach for at least 500m. The beach is rocky and uneven.
Thanks to Durham Heritage Coast for permission.