Porth Nanven - "Dinosaur Egg Beach"
Porth Nanven lies a short distance from Cape Cornwall, and is reached via St Just and the Cot Valley. It is a Site of Special Scientific Interest owing to the very large ovoid rocks or pebbles that gently cascade from the cliff and now form the beach and foreshore. In the distance is the twin-peaked islet called The Brisons, which lies one mile off Cape Cornwall, out of shot to the right of the picture.
Porth Nanven is sometimes referred to as 'Dinosaur Egg Beach' because of the remarkable deposit. These boulders come in all sizes, from hen's egg to a metre or more in length, and are now legally protected by the National Trust which owns the beach.
Many visitors assume that these weirdly shaped boulders are the work of the sea, which they are, but the sea of many thousands of years ago. Sea levels have changed several times since then and are now much lower than they were, causing the ancient beach to be suspended in the cliff high above the present level. Stand on the beach and look back towards the cliff, and you will see a wall of the rounded rocks waiting to break away and join those on the beach today (see below).
Or, to put it in scientific terms:
"The cliff and foreshore at Porth Nanven is important for Quaternary geomorphology
and stratigraphy, providing a particularly good example of an unusual type of raised
beach facies, namely a raised boulder beach. It comprises a coarsening-up sequence of
deposits with an upper two-metre thick layer of boulders (up to 0.6m long), overlying
four metres of smaller cobbles and gravels. The beach deposits are overlain by a
substantial thickness of fining-upwards head, with coarse angular boulders at the base.
The deposits at Porth Nanven demonstrate Quaternary changes in relative sea-level,
wave energy, sediment supply and climate."
Porth Nanven - "Dinosaur Egg Beach"
Porth Nanven lies a short distance from Cape Cornwall, and is reached via St Just and the Cot Valley. It is a Site of Special Scientific Interest owing to the very large ovoid rocks or pebbles that gently cascade from the cliff and now form the beach and foreshore. In the distance is the twin-peaked islet called The Brisons, which lies one mile off Cape Cornwall, out of shot to the right of the picture.
Porth Nanven is sometimes referred to as 'Dinosaur Egg Beach' because of the remarkable deposit. These boulders come in all sizes, from hen's egg to a metre or more in length, and are now legally protected by the National Trust which owns the beach.
Many visitors assume that these weirdly shaped boulders are the work of the sea, which they are, but the sea of many thousands of years ago. Sea levels have changed several times since then and are now much lower than they were, causing the ancient beach to be suspended in the cliff high above the present level. Stand on the beach and look back towards the cliff, and you will see a wall of the rounded rocks waiting to break away and join those on the beach today (see below).
Or, to put it in scientific terms:
"The cliff and foreshore at Porth Nanven is important for Quaternary geomorphology
and stratigraphy, providing a particularly good example of an unusual type of raised
beach facies, namely a raised boulder beach. It comprises a coarsening-up sequence of
deposits with an upper two-metre thick layer of boulders (up to 0.6m long), overlying
four metres of smaller cobbles and gravels. The beach deposits are overlain by a
substantial thickness of fining-upwards head, with coarse angular boulders at the base.
The deposits at Porth Nanven demonstrate Quaternary changes in relative sea-level,
wave energy, sediment supply and climate."