How do glaciers cause physical weathering of rocks?
Glaciers cause physical weathering of rocks through a process called abrasion. This kind of weathering occurs when rocks and sediments get embedded in the bottom of a glacier as it moves over the landscape. As the glacier advances, these rocks and sediments act like sandpaper, scraping against the underlying rocks. Over time, this friction and grinding action smoothens and polishes the rocks and breaks them into smaller pieces.
Additionally, glaciers exert great pressure on the rocks, further enhancing the physical weathering. As the glaciers advance, they push against the rocks and apply immense force to them. This constant pressure causes the rocks to crack, fracture, and break apart. As a result, the exposed surfaces of the rocks become more susceptible to other forms of weathering, such as frost wedging or chemical weathering.
Moreover, glaciers undergo a process called freeze-thaw or frost wedging. Water can seep into cracks and crevices in the rocks. When this water freezes, it expands, exerting pressure on the surrounding rock and causing it to crack. Over time, repeated freezing and thawing cycles widen and deepen these cracks, leading to the physical disintegration of the rocks.
In summary, glaciers cause physical weathering of rocks primarily through abrasion, where rocks embedded in the glacier scrape against the underlying rocks, and through the pressure they exert on the rocks, leading to cracking and fracturing. Additionally, freeze-thaw or frost wedging can further contribute to the physical weathering process.