What Is A Frost Weathering?
What Is A Frost Weathering?
Frost weathering is the process by which water freezing in ice causes mechanical weathering, which can take various forms, such as frost shattering, frost wedging, and cryofracturing. It can occur over short or long periods and at different scales, from breaking apart individual mineral grains to shattering large boulders.
This type of weathering is commonly seen in cold, high-altitude or high-latitude regions, including alpine, periglacial, subpolar maritime and polar climates, but can also happen anywhere where the temperature falls below freezing and there is water present.
Processes Of Frost Weathering
When water freezes in certain frost-susceptible soils or within the pores of rocks, it can cause the soil or rock to expand or heave. This is because the freezing water creates ice lenses that attract liquid water from the surrounding pores, which leads to the growth of larger ice crystals.
Over time, these ice crystals weaken the soil or rock, causing it to break apart. This process, called frost spalling, is common in humid, temperate areas with exposed, porous rocks like sandstone.
It can also affect asphalt pavements, leading to cracking and other forms of distress that, when combined with traffic and water infiltration, can cause rutting, potholes, and other roughness in the pavement.
Frost weathering, or the process by which rock is broken down by the expansion of freezing water, was traditionally thought to be caused by the volume increase of ice as it freezes. When water becomes ice it expands by about 9%, and under certain conditions, this expansion can cause rock to fracture or be displaced.
At temperatures of -22°C the pressure created by the expansion of ice can reach up to 207MPa, sufficient to break any type of rock. For frost weathering to occur through a volumetric expansion the rock must be completely saturated with water and frozen quickly from all sides, so that there is no air present to compensate for the expansion of the ice and the pressure is applied directly to the rock.
This process is typically limited to the top few centimeters of a rock’s surface and to pre-existing water-filled joints in a process called ice wedging. However, not all volumetric expansion of freezing water is caused by the pressure of the ice itself; it can also be caused by stresses in unfrozen water.
If the expansion of ice leads to stresses in the pore water that break the rock, the process is called hydro fracture. Hydro fracturing is more likely to occur in rocks with large interconnected pores or large hydraulic gradients.
If the pores in the rock are small rapid freezing of the water within them may cause the water to be expelled, and if the water is expelled faster than it can migrate, the pressure may rise, causing the rock to fracture.
Prior to the 1980s, it was generally believed that volumetric expansion was the main process behind frost weathering. However, this view was challenged in the 1980s by the publication of research by Walder and Hallet.
Nowadays researchers such as Matsuoka and Murton consider the “conditions necessary for frost weathering by volumetric expansion” as unusual. However the bulk of recent literature demonstrates that that ice segregation is capable of providing quantitative models for common phenomena while the traditional, simplistic volumetric expansion does not.
Effects Of Frost Weathering
Frost weathering is a physical weathering process caused by the repeated freezing and thawing of water in rock joints and small cracks. This type of weathering can have destructive effects on all types of rocks, from igneous to sedimentary.
Frost weathering causes large pieces of rock to break off or crumble away, forming small fragments called clasts, which are swept away by winds and water. It can also create small depressions or “potholes” on rocky surfaces, known as frostwedging.
Lastly, frost weathering can cause rocks to expand due to the formation of ice wedges within cracks and joints in rocks, which eventually leads to their breakdown.
Prevention And Mitigation Of Frost Weathering
Frost weathering is an important factor in the process of soil erosion and can be damaging to infrastructure and agriculture. Fortunately, there are ways to prevent and mitigate its effects. Firstly, good water management practices, such as proper drainage and irrigation, can help reduce the possibility of frost damage.
Secondly, avoiding planting near freezing surfaces can minimize the severity of frost weathering. Finally, protective measures like anti-icing materials, rock splints or baffles can help to shield vulnerable areas from frost weathering.
With these strategies in place, you can protect your home or other buildings against frost weathering and its destructive impact.
In conclusion, frost weathering is a type of mechanical weathering caused by the expansion of water when it freezes in small cracks and pores. It typically occurs in areas exposed to extreme cold temperatures.
Frost weathering can have significant impacts on landscapes, leading to fracturing of rocks and soil particles, landslides and hill-slope erosion. Understanding how frost weathering works can help us identify areas susceptible to potential damage and make informed decisions on how best to protect the environment.