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

Lime Kiln Sea Cave

The powerful stormy seas that batter this stretch of the Jurassic Coastline during the winter have undercut the limestone cliffs forming a series of spectacular sea caves. In one, Limekiln Cave, the sea has eroded the stone so thin that a section of the roof has fallen away. This is now covered with iron bars and gives an interesting view when the sea is really rough and demonstrates the forces of nature at work on this ever changing landscape.

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!

Limestone Grassland

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.

Birds

Over 300 bird species have been recorded around the Isle of Portland. Jutting out into the English Channel by 5 miles it is a magnet for migrating birds, the Bill provides a welcome resting point before moving on (The lighthouse seems to be a favorite perch!). The coastal cliffs provide a good vantage point to see many migratory seabirds as they move up channel to their northerly breeding grounds. Many other seabirds nest within the cliffs, while the abundance of food provided by the open grasslands and disused quarries are an ideal place to see insect and seed eaters.

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.

Derricks and Cranes

Portland has been heavily quarried, and there are several derricks and cranes scattered about the Island. Once used daily to load the stone on to barges, those that still work are are now tasked with the much lighter duty of launching the local fishermen’s boats.

Culverhole Mesolithic Site

Some of Portland’s earliest inhabitants lived at Culverhole in the Middle Stone Age around 7,500 years ago. Evidence of a settlement has been found in the form of a stone floor, walls and fireplaces. Interestingly, beneath a triangular stone in the floor, archaeologists found a pierced scallop shell, an axe head and a pebble. Part of a sacred ritual perhaps?

Medieval Strip Field Systems

Ancient Strip Field Systems cover Portland where crops would have been grown. They are generally found on hillsides, where the earth has been moved to maximise the drainage of the soil. They allowed crops to be grown in places that would otherwise have been difficult.