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Rocks

The Earth is old, really old, about 4,600 million years old. A lot has happened to the Earth in that time. The Earth has been crinkled by violent events such as earthquakes and volcanos, that have shaped mountains, valleys and deep ocean trenches. The Earth has also been smoothed by the erosion caused by weather and ice, filling up the valleys and trenches with the bits knocked of mountains, then solidifying into new sedimentary rocks.

For the last 600 million years or there about, life has also shaped the Earth and has left the remains of plants and animals in the sedimentary rocks some of these remains have become fossils. It is these fossils that make the Dorset and East Devon Jurassic Coast so important and why it has been designated a UNESCO World Heritage Site.

The rocks along the Jurassic Coast were laid down in what is known by the rock breakers (geologists) as the Mesozoic era which they then divided up into the Triassic, Jurassic and Cretaceous periods. It probably should have been called the Mesozoic Coast but it does not sound so good as Jurassic Coast (especially after Steven Spielberg's film Jurassic Park).

Since the layers of rocks of the Mesozoic era were laid down volcanoes or earthquakes have risen the west end of the Jurassic Coast and erosion has then flattened off the top to give us the coastline we have today.

Layering of sedimentary rocks.

During the Triassic period the first dinosaurs appeared and the first small mammals evolved. Very few fossils are found in the rocks from the Triassic period only some reptiles and sea creatures.

Primitive reptiles evolved into primitive birds and dinosaurs during the Jurassic period. In 1820 an extraordinary child named Mary Anning, aged 12, from Lyme Regis, discovered a strange fossilised 17 feet long, sea monster that we now know as an ichthyosarus in the cliffs of the Jurassic Coast. She found many more fossils over the next 35 years including a flying monster known as a pterodactyl and a plesiosaurus, another sea monster.

Dinosaurs dominate the the land during the Cretaceous period but they become extinct towards its end. Dinosaurs became extinct because the Earth became colder due to clouds of dust from either volcanoes or a large meteor impact, blocking out the sunlight. The dinosaurs could not survive the colder temperature.

As a result of the last 600 million years or so the Jurassic Coast has become an excellent place to search for and collect fossils. Please do not over collect fossils, leave some for others. Also do not dig or use hammers to break open rocks without permission from the land owners.

For more information visit the Jurassic Coast website for your complete guide to the UNESCO Dorset and East Devon Coast World Heritage Site.

Oil

Oil well at Kimmeridge

Oil, one of the most important fossil fuels, has also been found along the Jurassic Coast. There are working oil wells just above the beach at Kimmeridge Bay and Wytch Farm which is just north of Swanage. Prospecting for oil continues along the Jurassic Coast.

To the west of Kimmeridge at Ringstead Bay it has been known for the oil in the rocks of the cliffs to catch alight. Between 1826 and 1830 the part now known as Burning Cliff burned or smouldered providing a spectacle for tourists.

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