Thursday, November 30, 2006

Charmouth: The Pebbles


Saturday, November 25, 2006

Beer, Devon

Source: Photograph taken by Mark Whitworth and courtesy of the BBC

Thursday, November 23, 2006

The Rock beneath our feet!

Rock can be broadly classified into three types. Igneus, metamorphic and sedimentary, with the Jurassic Coast being of the sedimentary type

Igneus, is the rock that originates from magma within the earth's crust, produced by volcanic activity, when it is found on the earths surface
Metamorphic is the rock that is transported into the depths of the earth by geological processes, where it is heated and compressed. This process eventually changes its composition

Sedimentary rock is created by processes that occur on the surface of the earth, by the weathering of existing rock by water, ice and wind. Sedimentary rocks may consist of the organic remains of marine organisms (limestone), land plants (coal) or chemical reactions and evaporation (salt). Sedimentary rocks that constitute the Jurassic Coast are formed largely of the remains of marine animals. Sedimentary rock is often created by the weathering and re-deposition of pre-existing rock, with the parent rock being of igneus, metamorphic or sedimentary type. Rock particles, once created, are generally carried to distant locations by water, wind or ice, before sedimentation occurs

In past times of high sea levels, shallow seas have flooded deep inland and produced vast continent-wide limestone deposits. Chalk is a form of limestone, that developed in the Cretatious era. This rock was formed by millions of tiny plates of single-celled microorganisms called coccoliths. Over a few million years thier calcite plates piled up on the seabed to form a carbonate mud, which is now a form of limestone, up to 300 metres thick. This chalk forms the spectacular white cliffs of Southern England and North Western France

Any fossil content within a sedimentary rock will indicate its age and the type of environment in which it was deposited. Sedimentary rock often contains organic and inorganic materials. For example, early Jurassic black mudstone, found in the cliffs of Lyme Regis, contains organic material in the form of fish teeth and ichthysaurus bones. The mud itself is made of small inorganic rock particles, but its black colour suggests a high carbon content, the result of decomposition of the soft parts of organisms

Most sediment is deposited underwater, and is then buried further before it becomes rock. The exposure of marine sediment above sea level is due either to tectonic plate processes such as earthquakes and volcanic activity or to a general decrease in sea levels such as is associated with glaciation. Once sedimentary rock is exposed, weathering begins, particles are transported, and the cycle begins again

Tuesday, November 21, 2006

Saturday, November 18, 2006

Fossils on the Jurassic Coast

Fossils are the remains of animals and plants that have been preserved in stone and are the raw materials of the science of paleantology. Paleantology looks at the the direct evidence of fossils to study former life on earth and how it has changed over millions of years

The rocks that form the cliffs of Charmouth and Lyme Regis are rich in those animals that swam in the seas during the Jurassic period. As a result of landslides and winter storms, the area is rich in fossils that have been washed onto the beach. These fossils represent one of the richest snapshots of Jurassic life anywhere in the world

Geologists use fossils to help them identify rocks of a similar age, as rocks located hundreds of miles apart can be recognised as being of a similar age, according to the fossils that they contain. Ammonites are especially useful for this purpose as they evolved and changed rapidly (in geological terms), producing different species with distinctive shell forms. The Jurassic period has been dived into a series of Zones according to the appearance and disappearance of different ammonites

Mary Anning: courtesy of Wikipedia

Mary Anning (1797 - 1847) lived all her life in Lyme Regis and has been described as 'the greatest fossilist who ever live'. She collected fossils at a time when scientific enquiry was leading to a change in the way we thought about the evolution of life and our planet, which would culminate with the puplication of Charles Darwin in 'On the Origin of Species'

Mary collected fossils with her brother and father until the death of her father when she was aged 11. Mary took on the family business, becoming one of the most skilled of collectors, with an impressive knowledge of Anatomy. Her record of fossil 'firsts' is remarkable, leading to many eminent geologists of the day visiting the coast to learn from her work

Source: text
S0urce: graphics

Thursday, November 16, 2006

Lulworth Cove and Stair Hole

The coast around Lulworth Cove demonstates all stages in the development of bays and headlands, and how that development is controlled by the underlying geology. Along this section of the coast, the rocks have been tilted into a near vertical position

The oldest rocks, Portland Limestone, provides a barrier to the sea, behind which are progressively softer rocks, Purbeck Limestone, Lower Greensand, Wealdon Clay and Upper Greensand. The youngest rocks are chalk, which although soft are massive in thickness

The river that runs into the cove at one time reached the sea, through a cut in the hard Portland Limestone barrier. This allowed the sea to erode the Limestone. Once the sea reached the softer rocks behind, especially the Wealdon Clay, rapid erosion took place. Once the sea reched the chalk, erosion slowed, forming the perfect bay

To the west, the sea has been eroding the Portland Limestone at Stair Hole and the process of bay formation has just begun. Eventually lulworth Cove and Stair Hole will form one larger cove

Source: text

Wednesday, November 15, 2006

The Ammonite Path

Saturday, November 11, 2006

Gateway-Towns - Lyme Regis

The Jurassic Coast by its very nature is 95 miles long, but only a few metres wide. It is served by a handfull of towns, known as gateway towns. They are located very close to the Coast, providing serves for visitors such as hotels, guest-houses, restaurants, shopping facilities, museams and information

The clay cliffs around Lyme Regis are about 200 million years old, marking the start of the Jurassic period, capped by sandstone of about 100 million years in age. After heavy winter rains, huge mudslides flow onto the beach, where they are washed away by rough seas, uncovering the fossils

Lyme Regis is served by a Tourist Information Centre and Museum. You can also take boat trips from here, enabling the viewing of the Jurassic Coast from the sea, possibly the best way to see it

Saturday, November 04, 2006

Old Harry!

Silently Sleeping is the rock formation known as Old Harry's Rocks, located on the extreme South east of the Jurassic Coast