清水河两岸地形起伏,地面呈丘状或垅岗状,地表相对高差2—5米,有些垅丘已被风沙覆盖,植被茂密;而大多数垅丘上植被稀疏,灰白色亚粘土裸露,结构致密,表层干燥,丘顶偶见被砂及植物根系所充填的裂缝。这种地形发育在河两岸宽300—500米,顺河延伸10公里的范围内。经1980年现场调查,已确认上述的垅丘是高原上又一种类型的冻胀丘(图1)。 The topography of the Qingshui River is undulating. The ground surface is mound or jagged. The relative elevation of the surface is 2-5 meters. Some mound has been covered by wind and sand, and the vegetation is dense. Most of mound vegetation is bare with gray and white clay exposed. Dense, dry surface, the hilltop occasionally sand and plant roots filled by the cracks. This topography develops 300-500 meters wide on both banks of the river and stretches for 10 kilometers along the river. After 1980 field investigation, it has been confirmed that the above mound is another kind of frost heave on the plateau (Figure 1).