Ice is an incredible force, capable of shaping entire ecosystems through physical erosion processes. One such landform created by glaciers’ movements is known as “striations.” Striations is defined as scratches in rocks caused by glaciers dragging along these rock surfaces.
Pluckeding and abrasion are other major forms of glacial erosion. Both processes create classic mountain landscapes such as corries, aretes, horns, ribbon lakes, mountain-chained rock outcrops and crag and tail formations.
Plucking
As glaciers move across land masses, they create erosion that takes various forms – from scouring and plucking to silting up rivers.
Plucking occurs when stress from a glacier causes bedrock to fracture, then being taken up by its moving glacier as sediment.
Glaciers often transport rocks of all shapes and sizes – from large boulders to fine silt. This material is known as glacial erratics and it often stands out from its surrounding bedrock in terms of type, appearance and origin.
These types of erosion form the basis for many interesting glacial landforms, including lakes. Lake Winnipeg, Athabasca and Great Slave Lake ring the Canadian Shield like glacial erratics created by moving glaciers; similar processes also produced eskers and drumlins found throughout mountain landscapes.
Abrasion
Glacial abrasion occurs when glacial rocks of all sizes chafe against the mountainside and act like sandpaper to wear away at its rocks, leaving behind classic glacial landforms such as striations or polished rock surfaces.
Conditions necessary for abrasion to occur are quite specific: it only works on cold-based ice (not warm-based ice), and cannot occur in glaciers that have become attached to bedrock (such as glacial valleys).
Also, the amount of pressure exerted by a glacier on rock surfaces and how fast the glacier moves can impact how quickly abrasion takes place. When pressure levels are high, rapid abrasion occurs more rapidly and large chunks of rock are cut away at an alarmingly fast pace; when pressure levels are low however, slow erosion occurs with smooth surfaces created.
Freeze-thaw weathering
Glaciers’ ice can erode bedrock into landscape features such as fjords and cirques, creating landscape features such as fjords and cirques. Erosion is most efficient when rocks traversed are not too hard (Mohs scale of 1 or 2 at 0degC).
Freeze-thaw weathering or frost shattering is one method of erosion that plays an integral role in shaping corries’ back walls and helping create glaciated areas’ often chaotic landscapes. Water seeps into cracks in rock during warmer daylight hours before freezing at night, expanding as it freezes and pressing against it until finally it forces it apart through pressure of expanding ice. It’s one way that erosion contributes to shaping back walls of corries while simultaneously contributing to its crumbling surfaces that come to define their back walls’ back walls as it forms back walls of corries as it creates its back walls along with many of their features like corries’ back walls as it forms its back walls in corrie backwalls while creating landscapes such as those often found in glaciated areas.
Glaciers also pick up and transport rock debris as they move, known as entrainment. This process can cause further erosion when rocks are pushed by the ice onto bedrock surfaces to form deep grooves known as moraines that create further wear on it.
Sliding
Glaciers erode mountains and produce vast quantities of sediment that enter rivers and oceans, altering global sediment and biogeochemical cycles. Yet glacial erosion remains poorly understood owing to its highly dynamic nature – with huge variations in rate.
Quarrying and abrasion are the two primary forms of glacial erosion. Quarrying involves glacial ice fractured and crushing bedrock to fragment it further, before collecting these fractured or crushed pieces (known as clasts).
Abrasion refers to the process of wearing away rock surfaces by glacial ice movement. This typically manifests itself through scoring (striations) on their surfaces as well as silt-sized sediment formation. The intensity of abrasion depends on both basal sliding velocity and bedrock type; its intensity also changes over time.