At Botany Bay you will see two chalk stacks that have become separated from the mainland. They were formed when the sea exploited a crack in the chalk joints of the headland and formed caves. The sea then gradually eroded the joints and bedding planes of the caves creating an arch. Later on the stacks became separated from the mass of the headland.
The chalk forming both the headland and stacks is from the Cretaceous Period of the Mesozoic era. Chalk is a a soft white, porous sedimentary rock and by material the chalk is calcium carbonate and the rock itself is a very pure limestone. The chalk rock is formed from the fossilised remains of coccoliths, a microscopic algae mixed with tiny fragments of shells from organisms such as Bivalves and Sea Urchins. It takes 100,000 years to form just 1cm of chalk rock.
The chalk on this coastline can be up to 300m thick but only the top part is visible. The cliffs are from the top three zones of what is known as Upper Chalk. The top two zones are formed from species of Sea Lily or crinoids and the third zone is formed by the Sea Urchin.
To claim this Earthcache you are required to:
1. Have a photograph taken of yourself and/or your GPSr at GZ
2. E- mail me with the answers to the following questions
(a) How long ago was the Cretaceous period of the Mesozoic era?,
(b) which fossils form the chalk rock?, and
(c) how high are the stacks?
To e-mail me your answers just click on “His 'n' Hers” at the top of this cache page and then click on “send message” on the screen that appears.