夷平面是指各种夷平作用形成的陆地平面。夷平作用是外营力作用于起伏的地表，使其削高填洼逐渐变为平面的作用。自距今530万年到现在，冠豸山地区经历了多次间歇性抬升运动，每次抬升过后，便开始了新的风化侵蚀，或改造已形成的地貌，或形成新的地貌。这些地壳抬升的痕迹被系统地记录在了本区发育的四级夷平面上。 Planation surface refers to the land surface formed by various planation processes. The planation is the action of external forces acting on the undulating surface, which gradually cuts the higher part to fill in the lower part and finally turns into the flat surface. Since 5.3 million years ago, the Guanzhishan area has experienced intermittent uplift movements. After each uplift, new weathering erosion has been initiated, or the existing landforms have been transformed, or new landforms have been formed. These marks of crustal uplift are systematically recorded on the fourth level planation plane developed in this area.