Sediments of Carboniferous age occur in Kintyre in the district between the high ground of Southern Kintyre and the ridge of Northern Kintyre. The low ground stretching from Machrihanish to near Campbeltown is known as the Laggan of Kintyre. The Laggan runs in a series of terraces from the Atlantic to within a mile of Campbeltown, where the terraces give place to higher rounded knolls rising to a general height of 200 feet, and separated from each other by the highest raised beach. The chief platform in this plain is formed by the Machrihanish Water and its tributaries, the Backs and Chiscan Waters, and on both sides of this platform are the three terraces separating the 25-foot, 50-foot, and 100-foot raised beaches from each other and from the alluvial plain of the rivers. The 100-foot beach runs a considerable distance up the valleys leading to the higher ground to the north and south of the Laggan. To the extreme west, 3½ miles of sand dunes, higher than the plain behind them, give slight protection to the greatest stretch of cultivated land in Kintyre. Near the centre of the plain is a circular peat moss known as the Durry Moss.