Parking is available at the nearby National Trust Pay and Display car park. Free for NT members.
The beach at Birling Gap is set at the base of the imposing, sheer chalk cliffs known as the Seven Sisters. Despite being set between the well known seaside resorts of Eastbourne and Brighton this is one of the longest stretches of undeveloped coastline on England's south coast.
Birling Gap beach is a mix of mostly pebbles which give way to the occasional patch of sand. As the tide goes out rocky platforms are revealed which provide an array of rock pools to explore.
Access to the beach is via a sturdy tower staircase from cliff level.
The white chalk cliffs here are white for a reason, and that is the rate at which they are eroding; up to a metre a year in places. As well as meaning the cottages are falling into the sea the unstable cliffs also present a significant danger to anyone standing too close.
Birling Gaps cliffs are also of some geological interest and are a fine example of sedimentary layers.
Just over a mile east of Birling Gap the white chalk cliffs rise to to 531 feet (162m) above the English Channel below. This is Beachy Head, the highest chalk sea cliff in Britain.
The chalk at Seven Sisters belongs to the Upper Chalk, and was deposited during the Coniacian and Santonian stages of the Late Cretaceous period between 87-84 million years ago (mya). At this time Seven Sisters and much of Great Britain, along with Europe, lay beneath a relatively shallow sea around 40°N of the equator, on an equivalent latitude to the Mediterranean Sea today. In comparison with present-day conditions, global sea-levels during the Late Cretaceous were over 200 meters higher.
The higher sea levels likely reflect a combination of extreme greenhouse conditions and heightened plate tectonics (a scientific theory describing the large-scale motion of seven large plates and the movements of a larger number of smaller plates of the Earth's lithosphere, over the last hundreds of millions of years). Elevated plate tectonic activity and the associated volcanics delivered greenhouse gases to the atmosphere, fuelling the greenhouse effect. Global high temperatures melted much (perhaps all) of the ice at high latitudes, introducing significant amounts of water to the world's oceans. Uplift of the ocean-floor in regions of active plate tectonics displaced further water onto the continental shelves.
The evidence of higher sea levels is reflected in the white chalk at Seven Sisters. The purity of the chalk indicates its formation took place far from land, virtually free of terrestrial sands and silts that would otherwise have coloured it. Chalk is largely comprised of the the skeletal remains of planktonic algae known as coccolithophores which accumulated to form a white ooze on the seafloor.
This soft sediment was later compacted and hardened (lithified) to form chalk - a relatively soft rock itself. Today the chalk appears above sea level, the result of lower present-day sea levels and widespread uplifting caused by the pressure of the European and African continental plates colliding (generating the Alps), a process that took place at its greatest extent 30-25 mya.
More recently, following the end of the last ice age and subsequent increase in sea levels (albeit to a less extent than 84 million years ago), the coastline has moved inland, exposing the elevated chalk to intensive erosion and sculpting it into a vertical cliff-face.
One of the key markers visible in the cliff-face is the Seven Sisters Flint Band, a conspicuous dark-coloured sheet flint visible within the Seaford Chalk Formation. This particular sheet flint occurs near the cliff-base towards the River Cuckmere and appears intermittently on the foreshore towards Birling Gap.
Although flint is inorganic, the silica that formed it was originally sourced from the remains of sea sponges and siliceous planktonic micro-organisms (diatoms, radiolarians).
Flints are concretions that grew within the sediment after its deposition by the precipitation of silica; filling burrows/cavities and enveloping the remains of marine creatures, before dehydrating and hardening into the microscopic quartz crystals which constitute flint.
As this EarthCache is in an Site of Special Scientific Interest, please could visitors to the cache take care to not damage the geology, and to respect the countryside code while visiting the site by closing gates and following instructions on signs such as keeping dogs on leads etc.
To claim this EarthCache please email us or message through our profile the answers to the following questions:
1. What texture do the chalk in the cliffs have? (Take care not to damage the surface of the cliff whilst feeling the texture)
2. There are bands of other materials in the cliff face. How many bands are there and what are they comprised of?
3. Can you find examples of flint on the beach? Describe the colour and texture.
4. Estimate the height of the cliff at the given coordinates.
5. As an optional extra, please post photos of yourself at GZ, bonus points for those who can find stones with holes in to include in your photo!