In general, erosion takes place under most of the accumulation zone, whereas deposition predominates in the ablation zone. Destructive landforms are the results of erosion or deformation in which material is removed from the local landscape. Constructive landforms are created by building up material due to deposition or deformation. Both glacier ice and glacial melt water are active agents of glacial landform genesis. Mechanisms of glacial erosion Glacial erosion occurs in several ways.
Abrasion is the result of stones and grit in the basal ice grinding over the substratum.
This mechanism implies basal sliding and, thus, a temperate thermal regime with water beneath the glacier. Large blocks of the substratum may be removed by a process called plucking or quarrying. This takes place when blocks of the substratum become frozen onto the ice base and are lifted up into the glacier. Subglacial melt water is another important agent of erosion. High-pressure water charged with sediment may be highly erosive, and can carve potholes and distinctive hydraulic channel forms.