The swales are the depressions between the ridges. Flanking the high central ridges are two lower plateaus. Most islands have ridges ranging from , though Cat Island has a ridge in height. It consists of gently rolling countryside frequently broken by hills or low mountain ridges. Iturup consists of volcanic massifs and mountain ridges. This area is characterized by swampy lowlands punctuated by low hills, ridges, and volcanoes. Transverse ridges are formed by the union of two triangular ridges on posterior teeth. The species follows leading lines, migrating along inland ridges and coastlines. Pines predominate on the south sides of the ridges. It may have several concentric ridges or zones. The range includes the Ilmensky Mountains separated from the main ridges by the Miass River. The knee cap sliding across the bony ridges of the femur can cause some pain. These outer ridges are called cuestas. The soft sandstone is fragile, especially the ridges and ribbing of the Wave. These forests occur on the eastern ridges from .