How does ice wedging weathers rock

Mechanical weathering also called physical weathering breaks rock into smaller pieces. These smaller pieces are just like the bigger rock, just smaller. That means the rock has changed physically without changing its composition.

The smaller pieces have the same minerals, in just the same proportions as the original rock. There are many ways that rocks can be broken apart into smaller pieces.

Ice wedging is the main form of mechanical weathering in any climate that regularly cycles above and below the freezing point figure 2. Ice wedging works quickly, breaking apart rocks in areas with temperatures that cycle above and below freezing in the day and night, and also that cycle above and below freezing with the seasons.

Ice wedging breaks apart so much rock that large piles of broken rock are seen at the base of a hillside, as rock fragments separate and tumble down. Abrasion is another form of mechanical weathering. In abrasion, one rock bumps against another rock. Figure 3. Bacteria Some bacteria and other organisms secrete acidic solutions, which helps chemical weathering.

Different Weathering Types Help Each Other Keep in mind that you really can't separate physical from chemical or biological weathering, because all three proceed at the same time though not at the same rates, necessarily. With more surface area exposed, chemical reactions happen faster. Think of dissolving sugar in water. Sugar lumps will dissolve more slowly than the same amount of sugar which is granulated because the surface area is higher for the granulated sugar.

Try it if you don't believe me. Also, if slopes are flattened by physical weathering, water and soil can build up and thus speed chemical weathering. Chemical weathering helps physical weathering by weakening the mineral grains which make up rocks. This makes the rocks easier to break up by mechanical means. Biological weathering helps both, as I described above.

Trees fracture rock with their roots, which makes them easier to break up physically and exposes more surface area for chemical weathering. Bacteria which secrete acid solutions speed chemical weathering. Roots can force their way into even the tiniest cracks, and then they exert tremendous pressure on the rocks as they grow, widening the cracks and breaking the rock Figure 5. Although animals do not normally burrow through solid rock, they can excavate and remove huge volumes of soil, and thus expose the rock to weathering by other mechanisms.

Mechanical weathering is greatly facilitated by erosion, which is the removal of weathering products, allowing for the exposure of more rock for weathering. A good example of this is shown in Figure 5. On the steep rock faces at the top of the cliff, rock fragments have been broken off by ice wedging, and then removed by gravity.

This is a form of mass wasting, which is discussed in more detail in Chapter Other important agents of erosion that also have the effect of removing the products of weathering include water in streams Chapter 13 , ice in glaciers Chapter 16 , and waves on the coasts Chapter This photo shows granitic rock at the top of Stawamus Chief near Squamish, B.

Identify the mechanical weathering processes that you can see taking place, or you think probably take place at this location. Skip to content Chapter 5 Weathering and Soil. Exercise 5. To a geologist, an outcrop is an exposure of bedrock, the solid rock of the crust.