The Jurassic Coast.
Firstly to understand the Jurassic coast, understand Geodiversity.
Geodiversity is the range of rocks, fossils, minerals soils landforms and natural processes that make up the earths landscape and structure. Much of our coast is designated for its geodiversity The Jurassic Coast World heritage site was inscribed for its earth science interest. In geology the present is always a key to the past.
The Jurassic coast spans the dorset and east devon coasts and provides a window into the past. From Exmouth to Studland you can view rocks from mesozoic Era (triassic, Jurassic and cretaceous (250-65 million years ago) this represents 185 million years in 95 miles. It is diverse, providing access to to rocks formed in hor arrid deserts to tropical seas. The cliffs are a natural feature controlled by erosion.
The Jurasic coast between Exmouth in Devon and studland bay in dorset has been recognised as a unique and special place. The cliffs record 185 million years of the earths history in just 95 miles because the rocks tilt or dip down under the sea to the east. The oldest rocks at 250 million years in age are found in the west and the younger rocks for the cliffs in the east. This makes a journey along the jurassic coast like journey through time and teh constantly changing coast contains a wealth of different intersts in different places and from different times.
Now try and understand rocks.
Take any rock or stone and it has its own story to tell. Rocks range from thousands to billions of years old their stories can be very long but also incredible. With careful study a rock can tell you if its been melted, shattered, squashed, heated, dissolved, eroded, buried, scrapped, rolled, intruded or erupted. There are essentially 3 types or rock. Sedimentary
Sedimentary Rocks.
Some cliffs are made up of layer upon layer of soft mud, silt and clay built up over many millions of years. These are classified as ‘Sedimentary Rocks’, as they are made up of billions of tiny particles of sediment that have been turned to stone by millions of years of pressure from the layers above. Layers of sediment build up in lakes, rivers and the sea bed or even in deserts usually taking hundreds of thousands or even millions of years. If the layers of sediment stay buried they have a chance of being turned to stone. Minerals can fill up the gaps between tiny particles like sand and mud forming sandstones and mudstones. Alternatively the layers could become so squashed that all the grains of sediment are packed hard together and stay that way.
Between the Triassic , 250 million years ago, to the end of the Cretaceous, 65 million years ago, there was an almost continuous build up of sedimentary rocks across southern England. These layers were tilted by earth movements some time later and then uplifted. Subsequent erosion has formed a modern coastline that cuts through all those layers exposing the entire record at beach level. The oldest rocks are in the west and as you walk eastwards the layers in the cliff get younger and younger allowing you to ‘walk through time’.
Igneous Rocks
Igneous rocks are formed from lava or magma. Magma is molten rock that is underground and lava is molten rock that erupts out on the surface. The two main types of igneous rocks are plutonic rocks and volcanic rocks. Plutonic rocks are formed when magma cools and solidifies underground. Volcanic rocks are formed from lava that flows on the surface of the Earth and other planets and then cools and solidifies.
The texture of an igneous rock depends on the size of the crystals in the rock. This tells us if the rock is plutonic or volcanic. When magma cools underground, it cools very slowly and when lava cools above ground, it cools quickly. When magma and lava cool, mineral crystals start to form in the molten rock. Plutonic rocks, which cool slowly underground, have large crystals because the crystals had enough time to grow to a large size. Volcanic rocks, which cool quickly above ground, have small crystals because the crystals did not have enough time to grow very large.
Metamorphic Rocks
When rocks are heated up or put under a lot of pressure, they can change drastically. This is because the minerals that make up the rocks form only at certain temperatures and pressures. At high temperatures or pressures, the elements will rearrange their crystal structure to form a different mineral.
Graphite and diamond are two minerals that are both made entirely out of carbon. If we put graphite under a huge amount of pressure, the carbon atoms will be squeezed together and will rearrange themselves into the more compact crystal structure of diamonds.
This change happens without any melting of the rock. Everything remains solid while the metamorphism occurs.
Boat trips are one of the best ways to explore this spectacular coastline.
Exmouth- Jurassic coast
Orcombe point just east of Exmouth marks the start of the Jurassic Coast World Heritage site on the cliff top, prince charles opened the geoneedle in 2002 to celebrate the inuguration of the site. Here the rocks are a staggering 250 million years old and were formed in a baking desert. sailing east it is possibe to travel through 30 mllion years of earths history to sidmouth passing the fanouus Budleigh Salterton pebble beds (the remains of a giant river) redsandstone cliffs packed with nesting birds and the sea stacks at ladram bay
Budleigh Salterton - Triassic
Budleigh Pebbles are thought to be the most travelled pebbles in Europe. They started life over 400 million years ago in what is now Brittany in France. 240 Million years ago during the Triassic Period, they were transported by vast rivers to the south coast of England and in Budleigh. They formed the Budleigh Salterton Pebble beds. Today long shore drift causes some pebbles to continue their journey as far east as Kent.
Jacobs Ladders, Sidmouth - Triassic + Cretaceous
The Birth of the dinosaurs. Within these red rocks, experts have found evidence of reptiles such as Rhynchosaurus as well as the remains of amphibians and fish. Although the landscape was predominantly desert, there were wide shallow rivers supporting plants,insects and animals. It is believed that it was at his time that the first dinosaurs evolved as well as the first true mammals. The otter sandstone between Sidmouth and Budleigh Salterton is one of the richest sources of Mid Triassic reptile remains and ranks as one of the most important places in the world to fossils.
Beer and Seaton- Jurassic coast
The chalk cliffs at Beer are only 90 million years old and would appear to be in the wrong place, but leaving the sheltered bay, the underlying triassic rocks 220 million years old soon reappear The combination of impermeable clays and porous sandstone of chalk gives rise to landslides. The hooken landslide at beer head and the undercliff between Axmouth and lyme regis are fine examples and their huge scale can be appreciated from the sea. The great Bindon landslide of 1839 just east of Axmouth was the subject of teh first scientific description of such an event and created great interest. Even Queen Victoria viewed this spectacle from the royal yacht.Loy Boy 01297 23311 Mackerel trips and coastel trips from Seaton
Sambe, pleasure trips along the coast from beer to lyme regis with commentary, maximum of 11 passengers.
Branscombe pearl 2, mackeral trips and short coastal cruises from branscombe beach.
Lyme Regis- Jurassic Period
The dark cliffs around Lyme are around 200 million years old and mark the start of the Jurassic period. Fossils can be found on the beaches. The clifftops are capped by sandstone that is about 100 million years old and after heavy winter rain huge mudslides flow onto the beach where they are washed away by rough seas to uncover the fossils. Lyme Regis is a great place to find fossils. head to Monmouth Beach to see the Ammonite graveyard, a ledge which is exposed at low tide and is loaded with ammonite fossils.
Sunbeam, one hour trips along the jurassic Coast with commentary on a traditional open carved fishing boat.
Kraken, specialising in school trips, mackeral fishing trips. 07974796002
Charmouth - Jurassic
The Lower Jurassic clays in this part of Dorset are full of fossils that are washed out of the cliffs and left in the gravel and sand to be found by those who look carefully enough.
The cliffs at Charmouth are made up of layer upon layer of soft mud, silt and clay built up over many millions of years. These are classified as ‘Sedimentary Rocks’, as they are made up of billions of tiny particles of sediment that have been turned to stone by millions of years of pressure from the layers above
West Bay- Jurassic coast
The striking sandstone cliffs of west bay and Burton Bradstock are about 180 million years old. from the sea they are dramatic, especially in the evening sun. Great faults or fractures in the rocks are best seen from a boat To the east the huge bank of chesil beach runs for 28 kilometres to the isle of portland. The beach is composed of 100 million tonnes of pebbles and even contains Budleigh salterton pebbles from devon, showing that the sea has carried the shingle to the east.
Huntress 11, specialising in Dive and Scuba Charters and chartered trips around the bay for groups with prior booking, 07720 328251
Weymouth and Portland - Jurassic coast
Portland is an island of stone, composed of the world famous 140 million year old Portland Limestone. The rocks dip gently below the sea at portland Bill and passing this point by boat is a must if the weather is calm enough. Along the east weares, the grteat southwell landslide of 1734 is one of the largest recorded landslide events and it created church ope cove in the process. The calm waters of the fleet lagoon are internationally important for marine life and wildfowel.
Ferry step cruises, one hour cruise around portland harbour and the breakwaters.
Weymouth whitewater, fast one or two hour scenic rides with close up views around portland or along the coast to durdle door, lulworth cove or Worbarrow Bay from the Weymouth harbour The fleet observer, a glass bottomed boat specifically built to explore the fleet lagoon and Portland harbour. The hour long trips sail Daily. 07778 286892
Chesil Beach
Nothing can prepare you for your first sight of the "great beach" a 17 mile shingle bank which in one of the finest barrier beaches in the world. It has stood up to the mighty Atlantic Oceon for thousands of years and protects the Fleet, the largest tidal lagoon in Britain. When you explore Chesil Beach you will find that the pebbles in the west are far smaller than they are in the east, so tiny they are almost sand. This pebble grading is another unexplained mystery surrounding Chesil beach. It may be because the waves carry the larger rocks east because of there larger surface erea. Folklore claims that smugglers would now their position on Chesil by feeling the size of the pebbles.
Lulworth Cove- Jurassic coast
The spectacular coast around Lulworth is famous because here the rocks have been tilted into a nearly vertical orientation. This part of the chalg ridge that runds from Lulworth through to Corfe castle and beyond. The 140 million year old portland Limestone forms a barrier to the sea, but once breached softer rocks behind are rapdly eroded away to create a classic coastline of bays and headlands in every stage of their evolution
Durleston Head
Durlston Country Park is located just south of Swanage at the south eastern end of the Isle of Purbeck at Durlston Head. It is also a popular place for divers The cliffs at Durlston were also used as a quarry, but they are now closed as the cliffs have become too unstable. Now only seabirds and rare wildflowers remain. Bottlenose dolphins are regularly sighted from Durleston
Old Harry Rocks
Here you are at the eastern extreme of the world heritage site where the youngest cretaceous rocks dominate. The site ends just beyong the chalk headland of Ballard down and the white chalk sea stacks of known as old harry rocks. This beautiful erea of chalk downland and studland beach are managed by the National trust