Mount's Bay

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Mount's Bay and St Michael's Mount
View across Mount's Bay from Mousehole

Mount's Bay is a large, sweeping bay on the English Channel coast of Cornwall, in the far west of that county. It stretches from Lizard Point to Gwennap Head on the eastern side of the Land's End peninsula. Towards the middle of the bay (and probably the origin of the name) is St Michael's Mount. Several towns and villages on the shore of the bay are popular with holidaymakers, and a number of seaside resorts are found here.

Presenting a benign aspect to summer visitors of a large, scenic, natural harbour; in an onshore winter gale it presents a great danger to shipping as a "maritime trap". Especially in the days of sailing ships with an excess of 150 known wrecks in the nineteenth century.[1]


Mount's Bay is the biggest bay in Cornwall. The coast is approximately 42 miles from Lizard Point to Gwennap Head.

The half-moon shape of the bay is similar to that of Donegal Bay in Ireland and Cardigan Bay, although, unlike the aforementioned bays, Mount's Bay is relatively sheltered from the prevailing Atlantic westerlies.

Shipping hazard

The bay is capacious, sheltered and inviting. It is, however, a danger to shipping during onshore southerly and south-easterly gales.[1]

Storm beating Penzance

Sir Arthur Conan Doyle wrote in the Sherlock Holmes tale The Adventure of the Devil's Foot:

we looked down upon the whole sinister semi-circle of Mount's Bay, that old death-trap of sailing vessels, with its fringe of black cliffs and surge-swept reefs on which innumerable seamen have met their end. With a northerly breeze it lies placid and sheltered, inviting the storm-tossed craft to tack into it for rest and protection. Then comes the sudden swirl round of the wind, the blustering gale from the south-west, the dragging anchor, the lee shore, and the last battle in the creaming breakers. The wise mariner stands far out from that evil place.

Notwithstanding Conan Doyle's observations, Mount's Bay is a place of sailors and contains major fishing harbours, at Porthleven, Penzance and Newlyn.


Heading north and west from Lizard Point, the serpentine and hornblende schist cliffs reach a maximum height of 233 feet at Vellan Head and are only broken by small streams and coves such as at Kynance Cove, Gew-grade and Mullion Cove.[2] After Gunwalloe Fishing Cove the cliffs have the softer look of Devonian Meneage Formations of greywacke and mélange, with erosion a problem west of the naturally dammed ria of Loe Pool.

West of Porthleven there are high Devonian slate and granite cliffs to Rinsey Head after which the cliffs are topped by Pleistocene periglacial head and have eroded to form sandy beaches such as those at Praa Sands and Kenneggy. These beaches are in deficit and the cliff line is retreating.[3] With the exception of the harder Devonian dolerite and gabbro of Cudden Point, the low, eroding cliffs and beaches continue to Mousehole. This part of the bay is the most populated with the towns of Penzance and Marazion and the villages of Newlyn and Mousehole. Beyond Mousehole the granite cliffs, rise to 200 feet, and are broken by small streams such as at Lamorna Cove and Penberth.


There are small sand dune systems at Church Cove and Poldhu Cove, Porthleven Sands, Praa Sands and from Marazion to Eastern Green, Penzance. The former sand dunes of the Western Green are now covered by Penzance promenade. All, but Marazion to Penzance, are examples of bay dune systems which develop where there is a limited supply of sand trapped within the shelter of two rocky headlands.

Church Cove and Poldhu Cove are Sites of Special Scientific Interest[4] and also have associated climbing dunes which occur when sand is blown inland of the main dune system.[5]


Evidence of higher sea-levels in the past can be seen at Marazion where the town is built on a raised beach. A second example is the road between Newlyn and Mousehole. Sea levels rise and fall as the ice sheets advance and retreat, and raised beaches now mark the interglacial periods when sea levels were higher.[5]

Either side of Penzance, on the beaches at Ponsandane and Wherrytown, evidence of a 'submerged forest' can be seen at low tide in the form of several fossilised tree trunks. Geologists believe that a forest may have existed here before the most recent sea level rise. This correlates with the Cornish name of St Michael's Mount, Carrack Looz en Cooz — literally, "the grey rock in the wood".[6]

Raids from the sea

On 2 August 1595, a Spanish fleet under Carlos de Amésquita entered Mount's Bay and four galleys landed men at Mousehole. The Spaniards burnt Mousehole, Paul, Newlyn and Penzance; of Mousehole only one building was left standing.

In August 1625 "Turks took out of the church of Munigesca in Mounts' Bay about 60 men, women and children and carried them away captives".

The Lisbon Earthquake, 1755

On 1 November 1755, the Lisbon earthquake caused a tsunami to strike the Cornish coast at around 14:00. At Mount's Bay the sea rose ten feet at great speed and ebbed at the same rate. Little damage was recorded.

RFA Mount's Bay

Commissioned by the Royal Fleet Auxiliary in 2006, RFA Mount's Bay is the latest-design Landing Ship Dock, the Bay Class used by the Royal Navy. Mount's Bay has good affiliations with the Sea Cadet Unit TS Zephyr in Caterham, Surrey.

Outside links


  1. 1.0 1.1 Corin, J and Farr, G. (1983) Penlee Lifeboat. Penzance: Penzance and Penlee Branch of the RNLI.
  2. Lawman, J. (1994) A Natural History of the Lizard Peninsula. Pool: Institute of Cornish Studies.
  5. 5.0 5.1 Tonkin, B., Covey, R. and Moat T. (1997) Start Point to Land’s End Maritime Natural Area. A Nature Conservation Profile. Truro: English Nature.
  6. Pool, P. A. S. (1974) The History of the Town and Borough of Penzance. Penzance: The Corporation of Penzance.