Slickensided surface usually areas appear in clays, especially in extremely plastic clays, due to slip on critical shear planes. Due to shear displacement on unique planes, realignment of clay particles occurs parallel to the critical plane of slip. This leads to the development of a smooth surface with a dull luster known as a slickenside. The surface areas of the slickenside surface are weaker than the surrounding clay and the friction angle is very low. Therefore, the shear strength of slopes reduces significantly in that region, leading to an unstable slope.