Portland Bill Walk, Dorset

By Rebecca Coulson on March 4th 2010

This walk is taken from Walking the East Jurassic Coast – Portland to Studland by Robert Westwood. Published by Coastal Publishing at £4.95,
the book is available from mid-May 2010.

Distance 4 miles (6.5km)
Estimated time 21⁄2  hours
Difficulty An easy, level walk
Ascent 165ft (50m)
Map OS Explorer map OL15
Starting point SY693704

1 From the car park at Cheyne Weare follow the coast path south towards Portland Bill. You will have to follow the road for a short while before branching off on a track to the left marked ‘coast path’. Follow this all the way to Portland Bill, past a number of old quarry sites on the cliffs.

2 After exploring Portland Bill go round the lighthouse and follow the coast path to the west. Go across the grassy area next to the MoD buildings and then take the path that follows the coast.

3 At a stone marker just before the large buildings take the path to the right signed ‘East Cliff’. Follow this path, keeping left when it appears to split (follow the footpath signs). You will reach a road where you should bear right and then right again after a short while.
4 At the Eight Kings pub turn left at the mini-roundabout and follow the road back to the starting point.

The Isle of Portland is the classic location to see the Portland Stone. It is an ‘oolitic’ limestone, formed from millions of tiny spherical ooliths, created as layers of calcium carbonate grew around grains of sand or shell fragments, prompted by the rolling motion of waves and currents in a shallow, tropical sea. The layers would have formed as horizontal sheets on the sea floor, gradually accumulating over millions of years. As you walk past the limestone cliffs and the old quarry workings notice the varying thicknesses of the layers. Why do they vary so much? Layers occur because conditions alter. If sedimentation carried on consistently in an unchanging environment then a thick homogeneous layer would be the result. If conditions change this is reflected by a corresponding change in the sediment being deposited. It might be a variation in sea level or climate.The limestone layers of the Portland Stone, often over a metre thick, indicate relatively long periods of settled conditions. It is difficult to estimate the rate at which the sediment formed but typical rates are in the order of a few millimetres every thousand years. The Portland Stone was deposited in a high-energy environment, where strong currents rolled the sediment on the seabed backwards and forwards. One indication of this is the ‘cross-bedding’ that can sometimes be seen in the rocks. This appears as faint inclined layers cutting across other inclined layers, rather like the structure found in sand dunes. This is indicative of formation in a very shallow sea where the surface tidal movements extended down to the sea floor.

For more information:
Visit www.jurassiccoasttrust.org or www.jurassiccoast.com to download pictures of the Jurassic Coast on App for iPhones or iPod touch or download a podcast.
Charmouth Heritage Coast Centre has information about the Jurassic Coast and its fossils and runs guided fossil walks.
Lower Sea Lane, Charmouth
01297 560772, www.charmouth.org
Chesil Beach Centre is situated halfway along the Causeway from Weymouth to Portland, on the Portland Beach Road (A354); here you can learn about this remarkable barrier beach. The Centre also offers a variety of guided walks and talks for groups and families, a list of events can be found on the website.
01305 760579, www.chesilbeach.org
Lulworth Heritage Centre, Lulworth Cove, Wareham, is close to Durdle Door, Stair Hole and Lulworth Cove.
01929 400587, www.lulworth.com
Durlston Country Park, Lighthouse Road, Swanage  01929 424443

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