Walk through 185 million years of evolution...
The Jurassic Coast is famous for the record of prehistoric evolution contained in its rocks - and especially the dinosaur fossils.
It was Mary Anning who found and recorded the first complete dinosaur skeletons about 200 years ago. Today this 150 km stretch of coast, from Exmouth in Devon to Swanage in Dorset, is a popular holiday destination and a favoured location for geology and geography fieldtrips.
Among the different rock types that make up the coast is Kimmeridge Clay, most spectacular here at Broadbench. The unusual angular shape of the coastline is down to the particular character of Kimmeridge Clay. It is criss-crossed by many parallel cracks, called joints, and these determine the lines along which the rock is eroded, creating small jagged embayments. The joints are planes of weakness along which, over time, incoming waves trap and compress air. This in turn exerts huge pressure on the rocks causing them to split apart.
Broadbench is a surfer’s paradise with fantastic rollers up to 5m high. When the conditions are right, the waves will form tubes large enough for the surfers to ride inside. But why do these rollers form here on this stretch of coast?
It is because the rock has eroded down to a hard layer which creates a submerged broad, flat ‘bench’ near the shore. Waves moving over this bench are slowed down by friction at their base, causing the top of the wave to rise dramatically in height. A modest swell is turned into a serious surfing wave.
Surfing has enjoyed a big boom recently. According to the British Surfing Association the number of UK surfers has risen from 40,000 in the year 2000 to around 500,000 today.