Cache placed with the kind permission of The National Trust
Langdon Bay Flint: A Story from the Chalk Cliffs
Welcome to Langdon Bay, a quiet beach beneath the dramatic White Cliffs of Dover.
At first glance, the beach may appear to be covered with ordinary grey pebbles. However, these stones hold a story that began millions of years ago when this area was covered by warm sea.
The cliffs above are made mainly of chalk, formed from the remains of tiny marine organisms within this chalk, flint nodules developed over geological time. As the cliffs have been shaped by weather and coastal erosion pieces of flint have been released and transported by the sea, becoming the smooth rounded pebbles you see today.
Take a closer look at the stones around you. Their colour, shape, texture and even the lighter outer coating can reveal clues about their journey from the chalk cliffs to the beach.
This earth cache will explore:
- how flint forms within chalk
- why flint pebbles are common beneath chalk cliffs
- how waves and weathering change their appearance
- why beach flint looks different from freshly broken flint
Please remember: the pebbles are part of this natural landscape. Observe them but please leave them where you find them for others to enjoy.
Some More Technical Information
The White Cliffs of Dover form part of the famous English coastline reaching 350 feet high and facing the Straits of Dover and France.
Langdon Bay cliffs are made of chalk, a soft, white, fine-grained form of limestone interspersed with bands and nodules of flint. This chalk is composed of the microscopic calcium carbonate skeletons of tiny marine algae (coccolithophores) laid down during the late Cretaceous epoch (145 million to 66 million years ago).
The Geological Formations include:
1. The Lewes Nodular Chalk Formation which forms the primary accessible base of the cliffs and foreshore at Langdon Bay.
2. The Seaford Chalk Formation which appears higher up the cliff face, featuring distinct marker bands of flint. The Flint Nodules are dark-coloured horizontal bands and loose beach pebbles eroded from the upper chalk layers.
Important Note: Access to the EarthCache requires care and it is only accessible in daylight from 7am to 7pm at and around low tide. The route to the beach includes steep sections and uneven ground including a chalk zigzag path, tunnel and access to the beach is via a seven metre steep steel ladder. The chalk surface can become slippery when wet and loose material may be present. Please assess the conditions before continuing and only proceed if you feel comfortable. The return journey follows the same route back, so please consider your own ability and allow for the climb back. Coastal environments can change so take care near the cliff edge.
Please check the tide table for Dover before attempting this more challenging EarthCache.
Link to Dover tide tables can be found here: https://www.bbc.co.uk/weather/coast-and-sea/tide-tables/9/89
In order to log this EarthCache you must answer the following questions
- Describe how the flint nodules are formed within the chalk cliffs?
- Describe the dominant colour of the beach pebbles?
- Are they mostly light, dark or mixed?
- Measure the range in size of the pebbles found on the beach?
- Look closely at several pebbles. Describe their shape and surface texture. Are they sharp/angular or rounded/smooth?
- Freshly broken flint often has a shiny glass-like surface. Why do you think these beach pebbles often have a duller, rounded appearance?
- Why are flint pebbles common on a beach below chalk cliffs?
- Look carefully at the pebbles, can you see any white fragments?
- What is the shape of the pebbles with the white outer layer?
- Do you think the pebbles with a white outer layer (cortex) and those without it formed at different times? Explain your reasoning?
- Walk carefully across the pebble beach and notice how it feels underfoot. How does Langdon Bay feel compared with other pebble beaches you have visited? What characteristics of the pebbles might explain the difference?
- On your log please include a photo of you, or your GPS, or a personal item or your caching name at the Tunnel Entrance area immediately after the zigzag path (your face does not need to be visible).
Please send your answers at the same time as you log the cache via message or email. Cachers who do not send me an email with their answers (hopefully correct) will have their logs deleted.
The cache hider, The National Trust and/or Groundspeak accept no responsibility for any injury/damage/death that may be caused by attempting to retrieve this cache. If you do attempt this cache it is strongly advised that you take necessary precautions including avoiding visiting this cache during or just after inclement weather. No Cache is worth hurting yourself over!
Footnote: Photo's courtesy of Cache Owner (PPRDG0). AI Chatbot ChatGPT used to improve wording of questions.