The Aberystwyth grits consist of a series of interbedded grits and shales, of lower Silurian age, that are now exposed for about 30 miles on the western coast of Wales. Cliff sections are found over half the distance and provide the key to the structure. The grits were folded during the Caledonian orogeny, and most of the folds trend northeast. Compression was followed by a period of tension giving rise to joints and normal strike faults. During Armorican time, the primary compression was northeast-southwest and resulted in tension in a northwest-southeast direction, with formation of wrench faults, rejuvenation on Caledonian shear planes, and, later, development of joints. All the tectonic features are described.