A Car Free Day Out around St Austell EA03
Typical Cornish coastal scenery, old mines and 100,000 years of climate change (about 3km)
Take service bus 525 (every hour) from St Austell (Duke Street or bus/railway station) to Carlyon Bay Golf Course/Carlyon Bay Hotel bus stop. Walk down the road towards ‘The Beach’ and, after 250m turn left and proceed in an easterly direction on the South West Coast Path, which continues along the top of the cliffs.
Previous to 1835 high tides reached the cliffs below the path and a stream originating at Carclaze china clay works (near the conical tip on the skyline) brought waste sand down from the works across the low ground on your left and flowed into Par harbour. This caused unmanageable problems due to the sand blocking the harbour. So a tunnel was driven under the golf course to divert the sand-laden stream into Carlyon Bay. In a little over 100 years the beach was created; discharge of sand into the stream has now ceased.
In the 1930s the buildings on the beach formed part of an exclusive club, frequented by the Prince of Wales and others of his set. At the time of writing there are plans for a major development on the beach.
In the centre of the beach is a small stack known as ‘Crinnis Island’. Coastal erosion is very approximately a few metres per century, so several thousand years ago this stack could have been much larger, perhaps as much as 100m across, forming a highly defensible position for a settlement; so this may explain the proper Cornish name for this area, which is ‘Crinnis’, which is short for Caer Ennis – the camp on the island.
On your left is the golf course, which is on the site of an important copper mine – Pembroke Mine’, active in the first half of the 19th century. There is little sign of the mine workings now, although there are some mine shafts here, which you see marked by clumps of trees and bushes. One hundred and fifty years ago this would have been a scene of the utmost industrial dereliction.
At the far end of the sandy bay a footpath leads down from the coastal path onto a small headland known as Fishing Point. When you get down onto the solid rocky platform look back at the sediments resting on the bedrock, those immediately on top of the rock contain rounded pebbles of quartz, and this is the remains of a beach formed in the last temperate interlude between the colder periods of the Ice Ages, when sea level was about 8m higher than now, about 120,000 years ago.
Above the beach material is a brown material with angular slate fragments in it. The fragments are angular because they were formed by frost shattering, so this represents material known as ‘Head’ formed during the last Ice Age. Cornwall was not glaciated, but was very cold at that time. On top of the Head is a silty bown material with only a few stones in it – you climbed down a small gully in this material. This is the relic of a period from 20,000 to 15,000 years ago when the climate was very cold and dry. Due to the cold, large amounts of water were locked up in ice on land, which had the effect of lowering sea level by over 100m. This exposed large areas of what is now sea bed around Cornwall and the fierce dry winds picked up the silty sediments and blew huge dust clouds over Cornwall, which settled out to form this brown silty material, known as ‘Loess’.
Continue along the coastal path to Spit Beach where the raised beach is again spectacularly displayed. There are some features here of exceptional interest to climate scientists, as they show that at the height of the last Ice Age 20,000 years ago, the climate here was very cold – equivalent to the present day climate in northern Siberia or northern Canada.
A tarmaced path behind Spit beach leads northwards back to a footbridge over former clay works drying installations. Par harbour is just the other side of these drying units.
The valley at the footbridge was the site of the ‘Happy-go-Lucky’ tin stream works in the late 18th/early 19th centuries and the great mineralogist Philip Rashleigh in 1792 drew a wonderful section of the layers of sediment exposed in the tin opencast work. In the closing stages of the last Ice Age a kind of muddy flow moved down this valley during the summer thaws, which contained large amounts of tin. Overlying this ‘tin ground’ were a series of sands and peats. Sea level would have been much lower then. Remains of giant ox and deer were found in these sediments.
The old men worked this in an open pit which gradually migrated down the valley until, at about the site of the pedestrian bridge, the pit was over 30 feet below sea level. In 1801 a terrible storm broke through the bank which separated the tin pit from the sea and flooded the workings. Nothing daunted, the miners brought up iron rings 6 feet in diameter and placed one on the sandy beach. A barge full of rocks was brought up at high tide and moored on top of the ring. As the tide went out the weight of the barge pushed the ring down into the sand; then another ring was bolted on and the process repeated. Eventually the column of rings was 60 feet deep and resting on bedrock. The miners then excavated out the sand inside the rings and went down to work the ‘tin ground’ resting on the bedrock. At high tide this shaft stuck out of the water like a chimney. Working this loose sandy material under tidewater must have been very risky, but contemporary accounts tell that no lives were lost, although it was said some miners were ‘singed’ by the combustion of firedamp coming from the overlying bed of peat.
Just before a small bridge under the railway line continue straight on along the footpath alongside the main railway line. This brings you out alongside the main entrance to Par Docks. Continue into Par village where it is possible to catch the service bus 525 back to St Austell, alternatively continue to Par Station and catch a train.
At the end of this the participants should be thoroughly convinced that climate is not only possible but highly likely, because the evidence of what has happened in St Austell Bay over the last 120,000 years is so clear!
Colin Bristow, November 2009