Portland’s Geology

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

Nicodemus Knob

This 10 meter high pillar of rock stands on the cliff edge at the back of Waycroft Quarries. It marks the extent to which the convicts hand cut the stone from the Admiralties Quarries for use in the construction of the Portland Harbour Breakwaters. In all 6 million tonnes of stone was used in the scheme, most of it supplied by the free labour the convicts provided.

Bunnies

It is deemed unlucky to say “Rabbits” on Portland as they were often thought to be responsible for creating accidents by their digging undermining the stability of quarry workings. But despite being unpopular, their numbers thrive amongst the Great Southwell Landslip and the numerous disused quarries on the Isle.

Quarry Wildlife

Many of the disused quarries on Portland are protected, being sites of Special Scientific Interest. The habitat the old quarry workings provide to wildlife is unique. The abundance of limestone plants, rare orchids, grasslands and flowers that thrive here attract a host of insect life, many of which live amongst the damp rocks. The insects in turn attract a host of birdlife, for which Portland is famous.

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!

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.

The Portland Railway

The slopes of East Weare were the unlikely route for Portland’s public railway that transported passengers, goods and stone to the mainland.

High Angle Battery

The High Angle Battery was built to house fifteen canon to defend the approaches to Portland Harbour. They were strategically placed out of sight from the sea to prevent enemy ships from targeting them. Some of the guns weighed in excess of 20 tonnes and could engage the new breed of ironclad battleships at a distance of 5 miles (8 km).