Important Safety & Logging Information plus Access to the Beach
Access to the earthcache is by the beach. 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 tide times as published and keep an eye on the sea! It is not felt suitable for night visits.
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.
The listed coordinates are for Dead Mans Point (so called as an old mortuary stood here), you will find some signage here. You will then be required to walk approximately a quarter of a mile along the beach southwards to locate the Gin Cave.
To the east of County Durham sits a plateau of Magnesian Limestone which slopes gently towards the North Sea. This limestone was 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 rock was formed in a shallow landlocked sea which reached from present day northeast England to Poland.
Question to answer
What caps the Magnesian Limestone here and in which direction did it come from?
Temperatures at this time were much higher than today, this location sitting a little above the equator; due to the seas shallow and relatively calm nature mineral deposits were made as the sea water evaporated. The remains of reef structures are apparent in the fossil records and these can be explored at prominent hills such as nearby Beacon hill or the Tunstall Hills further north ( GC1WGF5 Sunderland's Barrier Reef)
Dome-like structures can be seen in the limestone at Black Hall Rocks in both the cliffs and foreshore. These were formed by mud being trapped in complex algae growths, similar to those that may be seen at Shark Bay (Western Australia). These can be observed just to the south of the Gin Cave.
Sea Cave - The Gin Cave (N54 44.601 W001 15.993)
Sea Caves (or Littoral caves) can be found in sedimentary, metamorphic and igneous cliffs. The largest examples being found in basalt (igneous) due to its inherent strength. Caves are formed by the action of destructive waves hitting the cliffs with great force. The action concentrates upon weak points within the rock, this may be a fault line or the bedding planes of sedimentary rocks, such as the limestone here.
Destructive waves are characterised by their height (compared to their length), strength of backwash and their frequency. A wave will grow in size as it travels uninterrupted by land, this distance is known as its fetch. A destructive wave hits the coastline at speed, the lower portion is slowed by the beach, the higher portion toppling forward as a ‘breaker’, crashing into the rock, with a downward motion. The action of the wave is not only attritional, with both the force of the water itself and any debris material carried therein (eg sand and pebbles), but much of the damage is caused by air being trapped in such faults and cracks being compressed. This hydraulic pressure is immense, weakening and shattering the rock as the air explodes back out. There is then a strong ‘backwash’ from the wave removing the material out to sea. The rocks erodes here much faster creating the cave.
Optional Task to Complete
Take a photo of the double arch entrance to the Gin Cave. Please include either yourself and/or your GPS in the photograph
Question to answer
The 'opposite' of a destructive wave is a constructive wave. What is their effect upon the coastline?
Caves in headlands may eventually erode right through to create an Arch in the rock. This will continue to erode and eventually the arch will collapse leaving a freestanding pillar of rock known as a Stack. The coastline here used to feature many stacks, well known features and often individually named such as the eye rock. These are no longer present through either natural causes or intervention by man. eg.The chair
LOGGING THIS CACHE
In order to log this cache:
(1) Upload a photograph of yourself and/or GPSr with the double arch in the background
(2) Send the answers to the 2 questions via our profile link at the top of the page
(Remember to check the box to include your email address for a response!)
Any logs made without an accompanying email within 14 days of the log may be deleted without further notice.
Access and Parking
Parking is free. There are a couple of parking spaces at Dead Mans point or alternative parking is available at N54 44.483 W001 16 162 (about 1/4 mile away) with a pleasant walk across the nature reserve.
Further Site Information Blackhall Rocks Reserve - Durham Wildlife Trust
