Mutton Cove is a popular climbing area. The cliff top has the remains of fossilized algal burrs that once surrounded the base of trees in a Jurassic forest. If you’re feeling adventurous, you can climb down the cliff a little way to where the blocks of quarried stone are stacked, to look at a remarkable deposit of calcite on the cliff face, “Flow Stone”.
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Flow Stone Calcite Crystals and The Portland Jewel
Calcite crystal formations found on the Isle of Portland
Hotspots: Portland’s Fossil Forest, Fossil Sea Bed
Portland’s Fossil Forest
Today there are very few trees on Portland but 140 million years ago there were forests growing here. The sea levels had lowered allowing soil to form which became colonized by plants and trees. Evidence of this remains today in the layer of fossilized soil “Dirt Bed”. This deposit of the “Purbeck Beds” contains the remains of a flooded forest floor. Fossilised rings of algae that grew around the base of the trees are often all that remain, though occasionally the wood itself has been petrified. A prime example of a fossilized tree graces the gardens outside the “Portland Heights Hotel”.
Fossil Sea Bed
Ripples of sand are frozen in time all over the Island. One of the best examples can be found on the cliff edge at West Weares, though seeing these is safest from the footpath.
Coastal Features: Portland’s Geology, Calcite Crystals and The Portland Jewel, Flow Stone
Calcite Crystals and The Portland Jewel
Rainwater flowing through Portland’s cracks and gullies slowly dissolves limestone from the rocks. Where a concentration of this Calcium rich water builds up, a deposit is formed, known as “Flow Stone”.
Pockets of this water may remain undisturbed allowing crystals of Calcite to develop. The crystals come in many different forms, the most spectacular being that of the “Portland Jewel”.
Rainwater flowing through Portland’s cracks and gullies slowly dissolves limestone from the rocks. Where a concentration of this Calcium Carbonate rich water builds up, a deposit is formed, known as “Flow Stone”. One of the best examples can be seen part way down the cliff at Mutton Cove, close the stacked quarry blocks of stone.
Portland’s dramatic landscape is shaped by the stresses placed upon it by the Weymouth Anticline, a huge fold thrown up during the mountain building period that created the Alps when the continents of Africa and Europe collided around 30 million years ago. The uplifting process tilted the Isle and created cracks and gullies that shape the towering cliffs to the west and the boulder strewn landslides in the east.
The uplifting of Portland has tilted the Isle so the cliffs on the west side are higher than those on the east.
This means the western cliffs erode in a completely different way from those on the opposite side.
The cliffs of East Weare are subject to large sprawling landslides, such as the Great Southwell Landslip, where the cliffs have fallen “down dip”, while the cliffs on the western side of the Isle tend to topple into the sea where they have fallen “up dip”.
All the falls and slides on either side of the island are parallel, following the cracks and fissures created
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Portland Bill Visitor Centre
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in this Area: Limestone Grassland, Butterflies and Moths
The limestone habitat of Portland’s grasslands creates colourful summer meadows full of wildflowers and butterflies. The dandelions and plantains that grow here are food for around 20 species of caterpillar.
Butterflies and Moths
Portland’s disused quarries, grassy wildflower meadows and landslips are a good place to see butterflies and moths. Of Britain’s 2,500 species of moth, over 800 have been recorded on Portland. In addition to moths, over half of Britain’s 57 different species of Butterfly have also been found here. While many live out their short lives on Portland, not all are permanent residents. Some are migrants, heading to our country from the continent to breed, while others are just incidental visitors, having been blown out into the English Channel until they reach the landfall of Portland - some have even been carried all the way from Africa!
Interest: The Portland Estate
The Portland Estate
Around 250 hectares of land on Portland are currently managed by the Crown Estate. This is part of the “Royal Manor of Portland” which has been in the of the Crown’s possession since Saxon times.
Around 160 hectares of the Estate is common land, which was traditionally used by the locals for the grazing of their animals and the removal of stone. The land is supervised by one of the last surviving Courts Leet in Britain, having been in operation since 800AD. Portland’s Court Leet meets on the third Friday of November every year, when matters involving income derived from fines and rents for the encroachment onto common land can be administered.