1. Basal sliding: This occurs when the glacier's ice base slides over the underlying bedrock. Melting water beneath the glacier helps to lubricate the surface and reduce friction. Basal sliding is the fastest mode of glacier movement and is most common in warm, temperate glaciers.

2. Internal deformation: Ice is a brittle material and can break under stress. When a glacier is subjected to stress, such as the weight of the ice above, it can deform internally. This type of movement is called internal deformation and occurs when ice crystals within the glacier slide past each other.

3. Surging: Some glaciers experience sudden, rapid movements called surges. Surges can occur when a large amount of water builds up at the base of the glacier, reducing friction. They can also be caused by changes in the glacier's geometry or by the presence of obstacles in the glacier's path. Surges can move glaciers at speeds of up to several kilometers per day and can cause significant damage to infrastructure and ecosystems.