Please be aware that the outer jetty does get spray from stormy seas. Please approach with caution (or not at all) at high tides and poor weather conditions. Coordinates are for the inner jetty which is much safer.
Stroller / Wheelchair access with caution, and possibly a bit of determination.
The Harbour.
Boscastle, with its little harbour, handled a large proportion of the trade between Bristol and the south western ports. In fact, the district between Boscastle, Tintagel, Camelford and Delabole was mainly dependent on the harbour at Boscastle for its supplies of coal and other imports. This trade was, at the time, carried out by sailing ships of up to 90,100 and 200 tons. These ships were mostly registered at the old port of Appledore. Some of their names were Saint Mary, Francis Drake, Whynot, Lively and Beddoe.
When ships entered the harbour it was fairly safe to enter in calm weather, provided the vessel was small and answered the helm quickly. If, however, there was a westerly or north-westerly gale there was no hope, for the entrance of the harbour would be a seething cauldron, waves lashing themselves against the confining rocks and them against each other, as in savage impatience at their inability to widen the passage.
In the days when ships carried cargoes to different ports and returned with coals, and sometimes timber, the approach was often difficult. It was never safe for ships to enter under their own sail, so on their arrival, a boat with nine men called “hobblers” would go out to meet them and tow them in to their berth.
It is very probable that the Phoenician traders came to Boscastle in the first or second millennium before Christ. It would be very interesting indeed if the truth of this could be established. No considerable tin mines are known to have been worked in the ancient world except those of Cornwall and a few of the Indian islands.
This was at the time before the island of Mechard Rock was disconnected from the mainland, when the cove was snuggled in what was then a natural breakwater,standing against the pounding, roaring and lashing of the heavy seas, which can beat with such terrific force all along the coast. When the outer part, which is now the island, became separated off is not known, but to the onlooker it can be seen that this was not an impossibility, with the constant lashing and power of the terrible seas. The Blowhole, or Devil's Bellows, will prove in time what the sea can do when the part with Profile Rock is separated from the mainland, the sea will then have full access to the harbour.
The Blowhole.
It is fascinating to see the force of water coming through a small hole at the bottom of the cliff situated inside of Penally Point. It is best seen when the tide is low, what is known as half tide, and if the sea is rough outside the Harbour, then it will show itself at its best.
When there are spring tides, that is when there are extremely low and high tides, the sea recedes almost level with Profile Rock or Penally Point and still the water will blow out. This goes to prove that there is a hole right through the cliff. Inside is a large cavern and when the water comes through from the outside, it strikes up against the side above the hole some feet above the exit, then with a rebound falling on the water which is still flowing toward the inside of the hole, and this is what causes the rush of water and the boom, sometimes it is a terrific bang. When you stand looking at the water coming through, first of all before the exit of the water, you can hear a dull thud and following that the blow through. When the sea is rough and at half tide the water and spray can blow almost across to the other side of the Harbour.
There is also a small blowhole on the inside of the island outside the Harbour. This can be seen when the sea is rough.Formation.
The rocks on this stretch of coastline are of Lower Carboniferous age, the result of storm dominated shelf deposition at the edge of the Rheic Ocean. The Rheic Ocean was one of the most important oceans of the Paleozoic Era. It lay between Laurentia and Gondwana from the Early Ordovician and closed to produce the vast Ouachita-Alleghanian-Variscan orogen during the assembly of Pangea.
In geology, a blowhole is formed as sea caves grow landwards and upwards into vertical shafts and expose themselves towards the surface, which can result in blasts of water from the top of the blowhole if the geometry of the cave and blowhole and state of the weather are appropriate.
There are 4 main processes that can lead to the formation of a blowhole.
Hydraulic action: The force of the waves compresses air pockets in small cracks in the rock, which upon withdrawal of the water expand rapidly causing the rock to crack further and eventually break.
Abrasion or Corrasion: Caused by waves bashing sea load (rocks, pebbles, sand, etc) into the cliff. The sea load dislodges loose and weak rock.
Corrosion or solution/chemical weathering: Rock, particularly limestone –which largely is composed of calcium-carbonate, is dissolved by acids in the seawater.
Attrition: Wave action causes loose rock debris to collide with each other, resulting in smaller and rounder particles, which in turn have a sandpapering effect on the rest of the rock.
Other possible processes are biological and volcanic processes or even human activity, but these are not applicable to the Boscastle Blowhole.
You may log this earthcache immediately after visiting, but the answers to the questions below are required within a reasonable time frame.
|
1. Of the four mentioned erosional processes, which is least likely to have contributed to the creation of the blowhole and why?
2. The nearby 'Profile Rock' is so named because of its resemblance to which famous person?
3. The island of Mechard Rock just off the coast was once attached to the mainland. Suggest a reason for its formation.
4. The sedimentary rocks approaching the viewpoint are unusual. Describe their appearance. Bonus points [optional] for suggesting why they are like this.
5. [Optional] Take a picture of a blow-out and upload with your log. Estimate the size of the blow-out; for this it might be helpful having something/-one (you?) of a known height in the picture.
|
Placed with kind permission of the National Trust. Also in a Site of Special Scientific Interest (SSSI).
The most exciting way to learn about the Earth and its processes is to get into the outdoors and experience it first-hand. Visiting an Earthcache is a great outdoor activity the whole family can enjoy. An Earthcache is a special place that people can visit to learn about a unique geoscience feature or aspect of our Earth. Earthcaches include a set of educational notes and the details about where to find the location (latitude and longitude). Visitors to Earthcaches can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth. To find out more click HERE.