The disused Chalk Pit at the above coordinates is located on the chalk escarpment, initially steeply rising up from the Thames to a height of about 100m before gently forming softer rolling hills south from the river towards Maidenhead. The Chalk Pit is a stunning natural oasis and the oldest geological site in Berkshire!
Chalk is formed from lime mud, which accumulates on the sea floor in the right conditions. This is then transformed into rock by geological processes: as more sediment builds up on top, and as the sea floor subsides, the lime mud is subjected to heat and pressure which removes the water and compacts the sediment into rock. If chalk is subject to further heat and pressure it becomes marble.
Chalk is white because it is formed from the colourless skeletons of marine plankton. The same is true of many limestones, so why aren't they all white? The reason is that most limestones contain impurities, such as clays sourced from the land, or organics, which give them colouration. The Cretaceous chalk is free from impurities because sea levels were very high, so there was little land exposed to supply other sediments, and as the continental margins were flooded most land was far away. The Cretaceous sea floor was also very active so any organics were quickly broken down. The result was a very pure lime mud, formed almost entirely of planktonic skeletons.
To validate your find pleae e-mail me answers to the following questions,
1. Provide a general description of the exposure.
2. Some of the Chalk is a slightly pinkish shade. What is this called and what is the cause?
3. Optional question - Trace fossils can be found in the scree. What form do these take and what caused these?
Please include with your e-mail, your caching name (e.g. metal-bijou) and your email address.
Don't worry about waiting for a reply before you log, in the very unlikely event that your answer is wrong I'll let you know so you can revise your answer or turn your smiley to a note.
The most exciting way to learn about the Earth and its processes is to get into the outdoors and experience it first-hand. Visiting an Earthcache is a great outdoor activity the whole family can enjoy. An Earthcache is a special place that people can visit to learn about a unique geoscience feature or aspect of our Earth. Earthcaches include a set of educational notes and the details about where to find the location (latitude and longitude). Visitors to Earthcaches can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth. To find out more click HERE.