How do cracks affect the rate of weathering

Imagine holding a pencil at each end and trying to break it. If you apply a much lower stress — enough to bend the pencil — and continue over a longer time you will still eventually break the pencil. Loads of experimental data from rock physicists have demonstrated the same thing is true of rock. Are any particular processes of mechanical weathering more significant than others?

The stresses that lead to mechanical weathering vary from location to location. Tensional pulling stresses are most efficient in the critical or subcritical cracking of any material, and tensional stresses in bedrock due to gravity, for example, will be larger on slopes than flat terrane. The environmental stresses that any rock experiences will also vary by geography, for example between the equator and the poles, or between the side of a boulder that experiences more sunshine and the other that is mostly in shadow.

In contrast, the suite of actual processes that break bonds, subcritically grow cracks and thus mechanically weather rock are likely universal for any given rock type. Thus by recognizing that most mechanical weathering is facilitated by subcritical cracking, we open the door to better understanding which combination of stresses, rock and environmental properties will lead to more significant mechanical weathering.

We are not there yet. This is true, but this limited view does not take into account the fact that mechanical bond-breaking at crack tips actually involves chemical reactions when stresses are low. The result is that those bonds become weaker just at that location and can therefore then be broken by the low stresses.

The process repeats, and slow subcritical cracking occurs. Because it is a chemo-physical process, any condition like temperature or humidity that might influence chemical reactions strongly influences the rate and efficacy of subcritical cracking.

Thus climate may have an enormous influence on mechanical weathering styles and rates above and beyond the influence that it has on which stresses may or may not be present. Freeze-thaw occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart.

Without weathering, geologic features would build up but would be less likely to break down. Weathering is the process that changes solid rock into sediments.

Sediments were described in the Rocks chapter. With weathering, rock is disintegrated. Begin typing your search term above and press enter to search. Press ESC to cancel.

Skip to content Home Physics Why does surface area affect the rate of weathering? Ben Davis May 14, Why does surface area affect the rate of weathering? What are 2 factors that cause differential weathering? Certain types of rocks are more vulnerable to chemical weathering, while others are more stable. Calcite is a type of rock that weathers quickly, due to the fact that it is rich in calcium. Rocks containing iron and magnesium also tend to weather rapidly, while quartz is a stable type of rock.

Biological interactions with bacteria and other organisms can increase the rate of chemical weathering. Chemical weathering can also help physical weathering by weakening the composition of rocks. This synergistic relationship works in the other direction too, as physical weathering can augment chemical weathering by creating smaller chunks of rocks and increasing the surface area available for chemical reactions.

Weathering is a natural phenomenon that is part of the carbon cycle of the planet. Ultimately, physical and chemical weathering lead to the production of soil , a process that takes millions of years. Soil is essential for all life on earth, as it provides water and nutrients to plants, which are at the lowest level of all food chains on the planet. However, human activities can and do accelerate the rate of weathering. Human activities like agriculture and construction can accelerate weathering and lead to erosion and flooding by breaking rocks and soils up, increasing the surface area of the ground that is vulnerable to weathering.

Burning fossil fuels also increases the rate of weathering by adding carbon dioxide to the atmosphere.