Dorset is the location of some fine geological sites, known as the Jurassic Coast, and designated as a World Heritage Site so we spent a day there with Richard Twitchett, a geologist from the Natural History Museum. The evening before Richard gave an overview of some geological concepts and an introduction to the geology of the area.
The rocks of this area are the sedimentary type, which are formed by accumulation of material compacted and cemented together over millions of years. These type of rocks may contain fossils of plants and animals that died and became trapped and preserved between the layers. The exposed rocks of the Dorset coast are Jurassic (200-145 million years old) and Cretaceous (145-65 million years old) in age. The rocks of Cretaceous age would have originally lain on top of the older Jurassic ones but earth movements have titled them so they become younger as you move east along the coast – like a walk through time. This entertaining video tells the story better than I.
First of all, we stopped by the Square and Compass pub in Worth Matravers to visit it’s small museum, sadly it was closed but Richard gave us a tour of the garden furniture which are constructed from slabs of local rock, including examples of dinosaur footprints and mud cracks.
Then we were off to Lulworth Cove, with Richard refreshing our minds on the age and type of rocks in this area from his introduction the night before. Lulworth is one of my favourite sites, but I’ve mostly had the misfortune to visit in the pouring rain, luckily today was beautiful day. Coves form when there are layers of rocks with different resistances, so a sea breach, maybe through a weakness in the rock, carves out the softer rocks behind. West of Lulworth Cove is Stair Hole, a smaller example which provides a glimpse of how Lulworth Cove formed.
Stair Hole features some amazingly tilted and folded rocks (called the Lulworth Crumple), so that in some places they are completely turned over.
Next we travelled West to Osmington Mills, were the cliffs form a rock sequence called the Corallian. As we walked along the shore Richard explained the different features of the rock and what this told us about the environments they formed in.
Some layers were full of fossil shells, dumped during ancient storms. Others were finer grained mudstones with many fossil traces of burrowing animals.
After a walk back along the top of the cliffs, admiring the views we set off back to the Old Malthouse for a very different evening activity – parasitology!