Wherever basal sliding takes place, the rock beneath the glacier is abraded and modified. As meltwater works into cracks in bedrock and refreezes, pieces of the rock are broken loose and frozen into the base of the moving glacier, a process known as plucking. While being dragged along by the moving ice, the rock within the glacier grinds away at underlying rock. The thicker the glacier, the more pressure on the rocks and the more effective the grinding and crushing. Pebbles and boulders that are dragged along are faceted, given a flat surface by abrasion. Bedrock underlying a glacier is polished by fine particles and scratched by larger, sharper particles. Striations and grooves on bedrock indicate the direction of ice movement. Grinding of rock across rock produces a powder called rock flour. Rock flour is composed largely of very fine particles of unaltered minerals. When meltwater washes rock flour from a glacier, the streams draining the glacier appear milky. Wherever basal sliding takes place, the rock beneath the glacier is abraded and modified. As meltwater works into cracks in bedrock and refreezes, pieces of the rock are broken loose and frozen into the base of the moving glacier, a process known as plucking. While being dragged along by the moving ice, the rock within the glacier grinds away at underlying rock. The thicker the glacier, the more pressure on the rocks and the more effective the grinding and crushing. Pebbles and boulders that are dragged along are faceted, given a flat surface by abrasion. Bedrock underlying a glacier is polished by fine particles and scratched by larger, sharper particles. Striations and grooves on bedrock indicate the direction of ice movement. Grinding of rock across rock produces a powder called rock flour. Rock flour is composed largely of very fine particles of unaltered minerals. When meltwater washes rock flour from a glacier, the streams draining the glacier appear milky.Wherever basal sliding takes place, the rock beneath the glacier is abraded and modified. As meltwater works into cracks in bedrock and refreezes, pieces of the rock are broken loose and frozen into the base of the moving glacier, a process known as plucking. While being dragged along by the moving ice, the rock within the glacier grinds away at underlying rock. The thicker the glacier, the more pressure on the rocks and the more effective the grinding and crushing. Pebbles and boulders that are dragged along are faceted, given a flat surface by abrasion. Bedrock underlying a glacier is polished by fine particles and scratched by larger, sharper particles. Striations and grooves on bedrock indicate the direction of ice movement. Grinding of rock across rock produces a powder called rock flour. Rock flour is composed largely of very fine particles of unaltered minerals. When meltwater washes rock flour from a glacier, the streams draining the glacier appear milky.Wherever basal sliding takes place, the rock beneath the glacier is abraded and modified. As meltwater works into cracks in bedrock and refreezes, pieces of the rock are broken loose and frozen into the base of the moving glacier, a process known as plucking. While being dragged along by the moving ice, the rock within the glacier grinds away at underlying rock. The thicker the glacier, the more pressure on the rocks and the more effective the grinding and crushing. Pebbles and boulders that are dragged along are faceted, given a flat surface by abrasion. Bedrock underlying a glacier is polished by fine particles and scratched by larger, sharper particles. Striations and grooves on bedrock indicate the direction of ice movement. Grinding of rock across rock produces a powder called rock flour. Rock flour is composed largely of very fine particles of unaltered minerals. When meltwater washes rock flour from a glacier, the streams draining the glacier appear milky.Wherever basal sliding takes place, the rock beneath the glacier is abraded and modified.