Earth cache information
Cretaceous white limestone, also known as chalk, such as is found at this location was formed between about 140 and 60 million years ago. This particular outcrop was formed towards the end of that period. It is made up of millions of skeletons and shells of long dead creatures deposited in of the floors of warm shallow seas.
This rock is also scattered with quite easily found fossils but you have to know what to look for. You may find evidence of small creatures in the rock face, look for flat sections of newly broken rock and you may be lucky enough to spot a skeleton or the shape of a shell. They are quite small. That however is not what I want you look for today.
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Also embedded in the rock you will find other, much larger objects which are the focus of Q2 below, here is a hint as to what you are looking for.
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Embedded in the white rock are strange fist sized objects which are a different type of rock. The exact mode of formation of these globules is not yet clear but it is thought that it occurs as a result of chemical changes in compressed sedimentary rock formations, during the process of diagenesis. .
One idea is that a gelatinous material fills cavities in the sediment, such as holes bored by sea creatures and that this becomes silicified. This hypothesis certainly explains the complex shapes of the nodules that are found. Certain types of this rock, such as that from the south coast of England, contain trapped fossilised marine flora. .
This rock is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, it is usually dark grey, black, green, white or brown in colour, and often has a glassy or waxy appearance. A thin layer on the outside of the nodules is usually different in colour, typically white and rough in texture .
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The actual name of this type of rock should be familiar to you but if not, it is on the notice board.
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So now you know what you are looking for and you should have enough information to answer the questions below.
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If you are still struggling, there is a notice board to the left of the entrance to the car park (as you look at the rock face) and the answers to question 2 and a lot more information is on this board.
Questions
This is a chalk cliff as can be told by the whiteness of the rocks but;
- Describe the features of the rock face, especially anything embedded in it.
- What is embedded in the rock face and how might this be useful to early human settlements? (Read the info above)
- How tall is the rock face at the location given?
If you feel willing and able, please include a photo of your visit, but be careful not to give away answers the answers above.
Thanks for visiting the cache and I hope you thought it was worth a stop.