Many of the stunning landscapes we enjoy today were formed through glacial erosion; examples include lush New England pastures and rolling Midwest farmland.
Ice itself may not be particularly efficient at erosion, but embedded rock fragments within glaciers may do considerable damage – this scoring of bedrock surfaces by these fragments is known as striation.
Plucking
Glacial plucking, glacial quarrying and joint-block removal are terms used to refer to the incorporation by ice of relatively large fragments of rock. This method can be an extremely efficient form of erosion when bedrock has numerous fractures or cracks present in it.
Glacial erosion works similarly to rubbing sandpaper against wood surfaces: rock particles stuck to glacial ice scrape against rocks beneath, gradually wearing away at them and leaving distinctive grooves known as glacial striations that distinguish the landscape.
Plucking, one of the key processes involved with plucking, can also shape the landscape by creating bowl-shaped corries and smoothed off peaks known as horns. While its rate may be difficult to anticipate due to rock breaking down under ice, its impact will depend on lithology of bedrock; particularly how many and wide-spaced its cracks are. Some rocks are more resistant than others to erosion.
Abrasion
Abrasion erosion occurs when glacier rock surfaces scrape against surfaces beneath. While ice itself doesn’t do much abrasion damage, small bits of rock called tools embedded within it act like sandpaper and act like sandpaper abrasion produces grooves in bedrock called “striations,” characteristic features of landscapes once covered by glaciers.
Glacial striations is often taken to be evidence of where glacier ice moved, since striations usually parallels its movement.
Horns form when multiple glaciers erode a single mountain peak at once. Additionally, horns may form when glaciers flow into U-shaped valleys called cirques originally created by rivers. Other features formed by glacial erosion include drumlin fields, eskers and kettle lakes.
Freeze-thaw weathering
Frost wedging occurs when water freezes and thaws repeatedly, gradually eating away at rocks through frequent freeze-thaw cycles, creating fractured surfaces on them that eventually crack and fracture into larger fractures over time. It is most frequently seen in glacial environments due to glacier debris being regularly dumped onto them by their glacier.
Erosion rates depend on whether or not a glacier is melting, with thickness having an effect. Erosion rates tend to be highest in areas where surface melt can reach bed through moulins unimpeded by supercooling constraints.
These factors mean that rapid erosion occurs only at locations and times where rock can be readily eroded, but nonetheless such erosion can create distinctive landforms like moraines and drumlins and increase sensitivity of other geological processes to glacier motion.
Melting
Glacial erosion is the gradual wearing away of rock by glacial processes, producing various landforms like U-shaped valleys, eskers, drumlin fields, and horns. Furthermore, glacial erosion leaves behind scratches known as glacial striations on rock surfaces that remain visible for years after.
Glacier erosion differs from wind or water erosion in that its effects take time to manifest themselves; you won’t immediately observe changes to your landscape.
Glacial erosion is limited by the availability of clasts for abrasion. Clasts are fragments of rock that range in size from silt to cobbles – these factors act to speed up glacial erosion rates.