How does weathering vary according to climate? Weathering is a natural process involving the breakdown of minerals, rocks, and soils into smaller particles.
Changing temperatures have a fracturing effect on rocks, leading to physical weathering.
Water can be used as a catalyst in this procedure. But, really, how does climate affect physical weathering? It does it in many ways actually.
Climate dictates weathering rate and type, as cold climates promote physical weather with arid regions having much slower weathering rates.
Different Types of Weathering
It is possible for rocks to be weathered in one of three ways:
- Physically, through processes like freezing and thawing
- Biologically, through the roots of living organisms breaking rocks
- Chemically, through the combination of carbon dioxide and water
Chemical weathering is rather complex and occurs after combining CO2 in the soil and air with water and certain rock miners.
The combination forms a weak acid, which eventually transforms the rocks into soil, silt, and sediment.
Fact: Rocks in hot and rainy regions undergo chemical weathering at quicker rates than rocks in cold and dry climates, as chemical weathering accelerates with rising temperatures.
Understanding More about Physical Weathering
Expansion and contraction of the top layer of rocks heated by the sun, or the periodic melting and freezing of water can cause physical weathering.
Physical weathering can be divided into two categories:
- Freeze-thaw is the process by which water gradually seeps into crevices in a rock, freezes and expands, and eventually breaks the rock apart.
- Exfoliation happens when fractures grow parallel to the soil surface because of the decrease in pressure during uplift and erosion.
Areas with scarce soil and few plants, such as mountainous terrain and hot deserts, are particularly susceptible to physical deterioration.
How Does Weathering Vary According to Climate?
Due to the differing rates of expansion and contraction of the various minerals within rocks, physical weathering is more common in cold regions.
Cracks form in rocks after they have been subjected to repeated heating and cooling cycles.
Extreme day-to-night temperature swings in arid and mountainous regions are responsible for the physical weathering that causes rocks to erode.
To put it simply, when organisms decompose rocks, this process is known as biological weathering.
Rocks, for instance, can be fractured by tree roots in the same manner that pavement can be buckled by them.
The Effects of Climates on Physical Weathering
Climates that are warm and humid are ideal for supporting life.
Think about the abundance of life in a rainforest vs. the dearth of life in the Sahara or the Antarctic.
Hence, warm humid climates like those found in the tropics have the highest rates of biological weathering, and the changing climate also directly impacts physical weathering.
Climate Affecting Weathering
Seasonal trends in a region’s weather are defined by annual averages of temperature, precipitation, wind, and sunshine.
Certain rocks weather more quickly in humid regions, whereas others are more easily damaged by erosion in dry climes.
In wetter regions, precipitation reacts with carbon dioxide in the soil to make a weak acid that dissolves the limestone, quickly forming fissures and valleys.
In contrast, sandstone deteriorates more rapidly in arid regions.
It is because its quartz content makes it resistant to chemical weathering but sensitive to cracking due to ice generated when water freezes and expands in the stone’s cracks.
Let’s talk more about these factors in detail to better understand how weathering varies according to climate:
Freeze-Thaw Cycles
Water that seeps into crevices in rocks or the spaces between soil particles freezes and then thaws, causing freeze-thaw weathering.
Because of the strong pressures caused by the water’s expansion, the fissures may enlarge or the soil particles may be pushed further apart.
The forces at work during frost breaking make it clear how this deterioration process might take place.
When water freezes, it expands by a little more than 9% in volume.
And the pressures created by this expansion, if contained, can exceed 220 MPa, which is more than enough to fracture the rock.
Thermal Expansion and Contraction
The weathering of rocks is affected by a wide range of climatic factors, including average temperature, precipitation, and insolation.
The rate at which rocks deteriorate due to mechanical and chemical weathering processes is influenced in large part by the ambient temperature.
Indirectly, temperature influences outcomes through influencing water-content fluctuations.
Several studies have shown that extremes in temperature, particularly those in the freezing and thawing ranges, considerably accelerate rock deterioration.
Thermal Stress and Physical Weathering
Thermal stress weathering causes a rock to break down due to expansion and contraction.
It contributes to the development of Earth’s landscapes alongside aeolian, fluvial, and chemical weathering.
Salt weathering as well as freeze-thaw are the most common forms of rock breakup on Earth.
Nonetheless, the thermal fracture is crucial in processes such as:
- Massive crack development
- Exfoliation
- Granular disintegration of larger rocks with water
An Important Consideration
Damage from thermal stress is primarily controlled by the rate of temperature change, or dT/dt.
Rocks are subjected to less extreme thermal strains when an atmosphere is present due to the attenuation of heating and cooling rates caused by sensible heat exchange and radiative processes.
Fact: Thermal stress and physical weathering are extremely common in the desert and in places where rocks are subjected to direct sunshine or heating due to wildfires.
Precipitation and Physical Weathering
Humid badlands see more quick and intense weathering, as well as higher rates of denudation, compared to arid or semiarid badlands.
The term “humid badlands” refers to a subset of badlands characterized by annual precipitation in excess of 700 m.
It also includes the dominance of freezing-thawing and wetting-drying cycles as the primary weathering mechanisms.
How quickly and severely a region’s physical environment ages depends largely on the frequency and nature of its precipitation.
For instance, in places where temperatures rise and fall frequently, heavy rains can increase the entry of water into rock cracks.
This increases the likelihood of freeze-thaw weathering.
An Important Thing to Remember
Physical weathering may proceed more slowly in areas with low precipitation rates.
Yet, even in arid regions, even trace amounts of precipitation can trigger weathering processes.
Condensation, such as dew or rain, can collect in cracks in the granite and contribute to freeze-thaw cycles, albeit more slowly.
Fact: Erosion and the subsequent migration of rock fragments can also be caused by strong rainfall events, which in turn can lead to even more fragmentation and abrasion.
Acid rain and Physical Weathering
Although climate change and acid rain are separate phenomena, they are intimately connected.
Rapid industrial and agricultural activity growth has increased the likelihood of acid deposition from SOx and NOx emissions.
This calls for more research into the impact of pH on water-rock interaction.
The degree to which soils and rocks are affected by acid rain is largely determined by their mineral makeup.
Soil with a low concentration of weatherable minerals will be unable to successfully neutralize incoming acid deposits through the release of base cations.
On the other hand, soil with a high concentration of weatherable base minerals will be able to do so.
An Important Thing to Know
Rocks high in quartz and muscovite are resistant to weathering regardless of the pH of the fluid, while rocks high in calcium (or magnesium) carbonate are more vulnerable to acid deposits.
Wind and Physical Weathering
Wind can also affect physical weathering, especially in locations with little vegetation and exposed rock.
Sand and other small particles the wind carries can abrade rocks and other geological structures over time.
The presence of sand particles makes desert and coastal habitats particularly vulnerable to wind erosion.
In addition, high winds can uproot loose rock pieces, carrying them for short or long distances and adding to the abrasion and fragmentation as they crash onto other surfaces.
Fact: Particle size and kind, as well as the frequency and direction of the wind, all play a role in how much of an impact wind has on physical weathering.
Takeaway
So, how does weathering vary according to climate?
Chemical weathering is more prevalent in regions with warmer, wetter temperatures, while physical weathering is more common in regions with colder, drier climates.
While weathering rates are lower in arid environments, mechanical erosion can be caused by flash floods.
What’s more, rocks and minerals undergo several types of weathering with varying degrees of intensity depending on the climate.
