The science of a beautiful landscape
The Dorset and East Devon Coast is well known to be very beautiful. The reason for that is in the relationship between the rocks and the sea.
A coastline takes shape through the sea and the weather pounding rocks and beaches over tens of thousands of years. The nature of a coastline depends on how the rocks and beaches react to the relentless energy from the sea and The Jurassic Coast has lots of different rocks that react in a wide variety of ways. The World Heritage Site is crammed with exceptional examples of natural coastal landforms of almost any kind imaginable. It is so rich in these features that scientists that study coastal landforms have described the World Heritage Site as an outdoor laboratory.
Scientists have spent years coming to study the landforms but many thousands of people come every year to enjoy the sheer beauty that all this variety creates.
Chesil Beach – the finest barrier beach in Europe
Location: Chesil Bank (West Bay – Portland) Best viewed from Abbotsbury Hill or New Ground view point, Portland.
Landform type: Long shingle bank up to 15m high made largely of chert pebbles.
Age: approximately 10,000 years
Where to go: Chesil is a very large landform. From the viewpoints of Abbotsbury Hill or New Ground on Portland you can get a sense of its size. You can go onto the beach at West Bay, Burton Bradstock, Abbotsbury, Ferry bridge or Chiswell on Portland. Some areas are protected and under restricted access to protect nesting birds.
A new Chesil Beach visitors centre will be opening in 2012. We need to expand on the centre once it is finished
Look out for: the pebbles that make up the beach are sorted by the waves so the small ones are at the western end and the largest ones at the eastern end. Chesil bank also supports its own unique plant and animal communities.
Building a beach
130,000 years ago sea levels were at a similar level to those of today and the cliff line of West Dorset would have been in almost the same position as it is now. During that time the landslides and mudflows that characterise that part of the Jurassic Coast would have been moving, carrying thousands of tonnes of debris on to the beach to be slowly removed by the sea. However, at about 125,000 years ago sea levels dropped due to the formation of ice sheets and the old coastline was stranded. The landslides continued to occur along the cliffs but without the sea to remove the fallen material it built up into massive debris fans. Eventually the slopes formed a stable angle, stopped moving and became vegetated. After 100,000 years the ice age ended and sea levels rose again to their previous height and began eroding the old landslides. The material was carried east by long shore drift creating the enormous shingle bank we see today. With the accumulated debris from the ice ages however, there aren't enough pebbles to sustain the size of Chesil bank and the huge beach is slowly shrinking. It will take thousands of years for it to disappear entirely.
Golden Cap – highest point on the South Coast
Location: a headland between Charmouth and Seatown, Dorset.
Landform type: 191m (626ft) high cliff.
Age: Cliff face formed in the last 10,000 years. The flat top of Golden Cap is a preserved land surface 50 million years old.
Where to go: You can get to Golden Cap by foot along the South West Coast Path or by a short walk from the National Trust Car Park on Langdon Hill.
Look out for: On a clear day from the top of Golden Cap you can see Dartmoor!
Aim for the flat-top!
The name 'Golden Cap' comes from the golden coloured Cretaceous sandstone that forms the top part of the cliff. The 'golden' cap sits on top of much older Jurassic rocks and there is an unconformity (link to unconformity info) between them.
When the towering cliffs of Golden Cap collapse in landslides thousands of tonnes of rock spill out into the sea. On a calm day from the top of the Cap old 'boulder arcs' can be seen stretching out under the water. These are the remnants of old landslides, and they can be traced 0.5km into the bay, showing how the cliff line has retreated over thousands of years.
The curious flat top of the Cap is a remnant of a very ancient landscape. 50 million years ago, during the Eocene Epoch this whole region would have been part of a plane, eroded flat over several million years. Some time in the last 40 million years the region was lifted up and rivers carved down into the plane leaving small patches preserved on hill tops. Golden Cap is one such place. To the north of the Cap there is a chain of flat top hills, all with flat tops, all acting like a memory of an almost vanished landscape.
Lyme Regis to Golden Cap – soft stuff
Location: West Dorset
Landform Type: Soft cliffs - a mixture of active landslides and mudflows supporting a nationally rare habitat type.
Age: recently active from around 20,000 to the present day
Where to go: It is dangerous to go up into the landslides and people have to be rescued from mudflows almost every year. Stay on the beach or on the coast path, away from the cliff edge.
Look out for: Fossils! Natural erosion here releases fossils onto the beach. Visit the Charmouth Heritage Coast Centre for more information.
Landslides to be proud of
This is an exciting part of the World Heritage Site. It demonstrates very clearly the important role of natural erosion in creating a place so special and worthy of protection. Scientists have been able to relate the way the cliffs collapse here to how the beaches below are maintained making it possible to monitor change and make predictions about what might happen in the future.
Landslides are a type of natural erosion and keep the geology of the World Heritage Site exposed to be studied. As well as playing this important role, the constantly shifting ground amongst the landslides and mudflows creates a habitat known as 'soft cliffs'. Soft cliff habitats are rare nationally and support several rare species of insect as well as a glorious variety of wild flowers and plants. Black Ven is the richest soft cliff habitat in the country. All these elements – the globally important geology and fossils and the nationally important habitat – rely on the constant activity of the landslides to be maintained. Without natural erosion we wouldn't have them, and we wouldn't have a World Heritage Site.
The Undercliffs National Nature Reserve
Location: Between Axemouth in East Devon and Lyme Regis in Dorset.
Landform Type: the 'undercliff' is a term used to describe the sloping section of coast between the top of the cliff and the beach. It is characterised by landslides that slowly, but continually move, giving rise to a rich mosaic of habitats.
Age: recently active from 20,000 years ago to the present day
Where to go: The Axemouth to Lymw Regis Undercliffs can only be accessed using the Saouthwest Coast Path. It is 7 mile stretch of rugged path that is difficult in places.
Look out for: Spectacular wildlife – wild woodland, nesting Peregrine Falcons and Ravens as well as various wild flowers and insects.
The torn land between the fields and the sea
The huge landslides that occur between Lyme Regis and Axemouth happen because of the geology. Chalk and sandstone above sit on clay and limestone below. The chalk and sandstone absorb water like a sponge, becoming very heavy, and move across the impermeable and slippery surface of the clay beneath. This often happens slowly, pushing rock and soil before it, causing breaks in the established paths and pushing trees over. Occasionally it happens in spectacular fashion as it did in 1839 When Goat Island was formed.
The Bindon Landslide of 1839 was a famous event at the time. One night, a huge slab of land, known locally as goat Island, moved towards the sea and a large chasm opened up behind it. The front of the landslide was lifted up out of the sea creating a small natural harbour, although this was quickly eroded away. Today, Goat Island and the chasm are two of the most noteworthy features within the Undercliffs.
The National Nature Reserve is managed by Natural England to preserve and protect the amazing wildlife that lives there.
Hooken Landslide
Location: between Beer and Branscombe, East Devon.
Landform Type: Landslide in Chalk.
Age: formed in 1789
Where to go: Hooken landslide is a short walk west from Beer. Sturdy footwear and great care is needed when attempting the footpath down through the landslide. Beer is on the X53 bus route.
Look out for: Peregrines perched on top of Chalk pinnacles, the nationally rare 'Purple Gromwell' plant and evidence for coppiced ash trees that pre-date the landslide.
A deep landslide
Hooken landslide occurred because the here Chalk sits on top of slippery clays from the Triassic period. These are buried deep under ground but it is here that the rocks gave way, causing the dramatic landslide above. Today the landslide is relatively stable and a well established path runs through it.
Budleigh Salterton Beach – Pebbles from the past
Location: Budleigh Salterton, East Devon
Landform Type: Large pebble beach
Age: Formed some time in the last 10,000 years, after the last ice age
Where to go: Budleigh Salterton is on the main bus route between Sidmouth and Exmouth and is easily reached by car.
Look out for: Pink pebbles – these uniquely coloured pebbles only come from this beach and nowhere else in the UK. Removing any comes with a fine of up to £2000!
Pebbles from the past
All the pebbles that form the ebach at Budleigh Salterton come straight out of the cliff. There is a lyer of rock here made up of these pebbles and is known as the 'Budleigh Salterton Pebble Bed'. The pebbles were once carried by a river nearly 250 million years ago before being deposited and buried. Now they are eroded out of the cliff to form the beach. They are made of a very hard rock known as quartzite.
This beach is special because it allows scientists to investigate, in detail, the relationship between the supply of pebbles and the size and nature of the beach they make up. It is also free of any major coast defences and so lets us study how a beach behaves naturally, without being interfered with by human beings.
Ladram Bay
Location: Ladram Bay, East Devon
Landform Type: Naturally formed sea stacks
Age: Triassic, 245 - 235 million years old
Where to go: You can get to Ladram bay by foot along the south West Coast Path or by car via the Ladram Bay Holiday Park.
Look out for: Sea birds on the rock stacks.
Resisting the Sea
The cliffs and stacks at Ladram Bay are made up a red coloured soft sandstone that formed in deserts during the Triassic period. The layers of sandstone are harder in some places than others. These harder areas resist erosion from the sea whilst the softer rock is worn away around them. Eventually the harder parts of the sandstone stand entirely free of the cliffs – these are known as sea stacks.