Glaciers:
* Erosion: Glaciers are like giant bulldozers, grinding and scraping the bedrock they move over. This process, called glacial abrasion, can break down rocks into smaller fragments, creating glacial till - a heterogeneous mix of rock debris.
* Transportation: Glaciers transport these rock fragments over long distances. As they melt, they deposit the debris, creating moraines (ridges of sediment) and outwash plains (flat areas of sorted sediment).
* Weathering: The freeze-thaw cycles within glaciers can also contribute to physical weathering, breaking down rock into smaller pieces.
Rivers:
* Erosion: Rivers carve channels through rock, using the force of flowing water and the abrasive power of the sediment they carry. This process can create features like canyons and valleys.
* Transportation: Rivers transport sediment downstream, often depositing it in different locations. This process can create alluvial fans, deltas, and floodplains, which are areas with distinctive sediment types.
* Chemical weathering: Dissolved minerals in river water can contribute to chemical weathering, altering the composition of rocks.
New Rock Forms:
Although glaciers and rivers don't create new minerals, their actions can lead to the formation of new rock types, particularly sedimentary rocks. Here's how:
* Glacial Till: The unsorted, heterogeneous mix of rock fragments in glacial till can be cemented together by natural processes, forming a type of sedimentary rock called tillite.
* Outwash Deposits: The sorted sediment deposited by glacial meltwater can form sandstone, conglomerate, or claystone, depending on the size and composition of the sediment.
* River Deposits: The sediment deposited by rivers can form a variety of sedimentary rocks, including sandstone, conglomerate, mudstone, and limestone.
Key Point: The processes of erosion, transportation, and deposition by glaciers and rivers are responsible for shaping the landscape and creating new rock forms, but they don't fundamentally change the chemical composition of minerals within the rocks. They are powerful forces of change, but the new rock types they create are formed from existing mineral materials.
