Machair
On the western seaboard, low and flat windswept sand plains known as Machair are found. Machair consists of a mixture of siliceous sand derived from the shells of animals which lived on the offshore platform.
This machair plain lies behind a shingle beach and a system of low dunes. The wetter areas of machair support low-growing mats of mosses and liverworts. To the South-East of this plain the ground rises sharply and these hills are covered by a blanket bog and heath. This vegetation is unusual for its community of mosses and liverworts known as the Northern Atlantic Hepatic Mat community.
On Achill this community descends to its lowest altitudinal level in Ireland. On the seaward side, the land slopes steeply to the sea, forming impressive cliffs. Here the damp rocks support rich communities of mosses and liverworts.
The Keel Machair/Minaun Cliffs site is of ecological interest due to the range of habitats to be found there and particularly for population of Whooper Swans which frequent Keel Lough. The coastal oceanic and montane communities of mosses and liverworts are of international importance.
Behind the dunes is usually a gently sloping plain whose degree of flatness is a reflection of age. The level of the machair plain is controlled by the underlying water table. This is the reason that many machair areas are flooded during winter. A seaward escarpment marks the landward limit of the plain. Machair is a completely vegetation covered coastal plain, marram and lyme grass being the most common varieties found.
Sand Dunes
Sand carried inland by onshore winds is deposited in a streamline form around some obstacles. Plants then colonise these small mounds of sand. As sand deposition proceeds, their foliage creates even more deposition and the root network binds the sand into low embryo dunes. As these dunes grow in height they coalesce parallel to the shoreline. In turn they are colonised and stabilised by other establishing plants and the dunes continue to grow.
Dune Erosion
Almost all dunes are subject to erosion, most commonly caused by “Blow-outs”. This happens when the wind gains access to the sand beneath the vegetation at the crest and rapidly erodes the surface causing a depression. As the wind is channelled into is the depression grows until its width reduces the channelling effect of the wind, leaving low-lying rolling dune pasture called Machair.
Frontal erosion occurs when the entire seaward face of the dune system is cut back by storm waves. This can be recognised by a steep slope of loose sand and slipping clumps of crestal vegetation.
Storm Beaches
In times of storm, the erosional function of waves is greatest but it is also during storms that Storm Beaches are created. Cobbles, pebbles and boulders are hurled up on to the shore, usually further inland than the level usually reached by high spring tides. The coarseness of this material usually ensures that the backwash of the retreating waves is reduced so that smaller material moves back down the beach. When the storm subsides, the deposited boulders remain where they were thrown, out of reach of the sea.
Deposited material is never sorted by size and so storm beach material is varied in size although the stones and boulders are usually rounded and smooth from the abrasive action of the waves and the finer material suspended in water.
Bird Life
Waders such as the Snipe, Lapwing and Oystercatcher are frequently spotted in this area.
The Gull family is well represented with the Common Gull, Kittiwake, Blackheaded Gull, Great Black-backed Gull, Lesser Black-backed Gull and Herring Gull all visitors to the beach.
Terns are also sighted with the Arctic Tern, Common Tern and Sandwich Tern being the most commonly noted.
Cormorants and Shags have also been spotted.
Extracted from: www.mayo.ie