Although this section is mostly about chemical weathering (carbonation), you could be asked a question about both physical and chemical weathering, and you will need to be able to write 6-7 SRPs about mechanical weathering (freeze thaw action), so make sure you learn this. Hydrolysis and exfoliation are often mentioned in the short questions so be able to recognise photographs of this process. You should know how limestone is formed, and it's structure, be able to explain carbonation and how it weathers limestone. You should be able to write about the formation of a limestone pavement for a surface feature, and a limestone pillar for an underground feature. It is also possible to use your knowledge of The Burren to answer the question of unique geomorphological areas if it comes up in the Regional Geography section.
1. Hydrolysis (Chemical Weathering)
Hydrolysis is a type of chemical weathering where minerals in rocks react with water, causing them to break down into clay and other substances.
It commonly affects rocks like granite, where feldspar turns into clay.
2. Exfoliation (Physical/Mechanical Weathering)
Exfoliation is a type of physical weathering where outer layers of rock peel off due to temperature changes between hot days and cold nights.
It is most common in desert climates, where rocks expand in heat and contract at night, causing layers to crack and fall off.
3. Freeze–Thaw Action (Physical/Mechanical Weathering)
Freeze–thaw action is physical weathering that occurs when water enters cracks in rocks, freezes and expands.
This expansion puts pressure on the rock, gradually causing it to split and break apart over time.
4. Carbonation (Chemical Weathering)
Carbonation is a type of chemical weathering where carbon dioxide in the air dissolves in rainwater to form weak carbonic acid.
This acid reacts with calcium carbonate in limestone, dissolving the rock and helping form karst landscapes.
The Next 3 Videos Revise Physical Weathering - Learn Freeze Thaw Action Well
Weathering Questions (1).pdfWeathering Questions with marking-scheme (1).pdfYou should know Limestone Formation & Structure for this section:
1.
Limestone is a sedimentary rock made from the remains of marine organisms
(S) These remains, such as shells and skeletons, accumulate on the seafloor.
(D) Over millions of years, they form thick layers called strata.
(SE) This leads to the formation of limestone layers.
2.
As more layers build up, the weight compacts the sediments
(S) Calcite from the organisms acts as a natural cement, binding the particles together.
(D) This process, called lithification, turns soft sediments into solid limestone.
(SE) This forms compact limestone rock layers.
3.
Carboniferous limestone in Ireland was formed around 350 million years ago
(S) During this time, Ireland was covered by shallow tropical seas.
(D) The Burren in Co. Clare is an exposed example of Carboniferous limestone.
(SE) This period shaped much of Ireland’s limestone geology.
4.
Limestone is composed mostly of calcium carbonate (CaCO₃)
(S) This makes it susceptible to chemical weathering through carbonation.
(D) This reaction helps create features like limestone pavements.
(SE) This process shapes karst landscapes like the Burren.
5.
Carbonation occurs when rainwater absorbs CO₂ from the atmosphere, forming weak carbonic acid
(S) This acid reacts with calcium carbonate in limestone, dissolving it.
(D) This leads to features like grikes and clints.
(SE) The Burren's landscape is a prime example of this process.
6.
In Ireland, limestone can also form distinctive underground features
(S) Carbonation can create caves, stalactites, and stalagmites over time.
(D) An example is Aillwee Cave in Co. Clare.
(SE) These underground features are common in karst regions.
7.
Limestone is a pervious rock, meaning water can pass through its joints and bedding planes
(S) Unlike porous rocks, limestone allows water to flow through cracks.
(D) This contributes to the development of karst landscapes.
(SE) Water seepage through limestone forms underground features.
Limestone Pavement - A Surface Feature In The Burren, Co Clare (A Karst Region)
Physical Weathering: Freeze-Thaw Action (7 SRPs)
1.
Freeze-thaw action occurs in areas where temperatures fluctuate above and below freezing
(S) This process is common in high-altitude regions like Croagh Patrick in Co. Mayo, where daily cycles of freezing at night and thawing during the day are frequent.
(D) This temperature fluctuation drives the freeze-thaw cycle, breaking down the rock over time.
(SE) Freeze-thaw weathering is a significant force in the physical breakdown of rock in cold climates.
2.
Water enters cracks in rocks during warmer periods
(S) Rainwater or melting snow seeps into cracks and joints in the rock.
(D) The water remains in these cracks when temperatures drop, allowing the freeze-thaw process to begin.
(SE) This repeated process is key in disintegrating large rock formations.
3.
When temperatures fall below freezing, the water in the cracks freezes and expands
(S) The water expands by roughly 9%, exerting pressure on the surrounding rock.
(D) This pressure forces the cracks to widen, gradually breaking the rock apart.
(SE) This expansion and contraction lead to gradual fragmentation of the rock.
4.
Repeated freezing and thawing cause cracks to grow larger over time
(S) The continued cycle of freezing and thawing weakens the rock, causing it to fracture.
(D) Over time, the repeated action leads to the formation of rock fragments.
(SE) This cycle is responsible for the creation of scree slopes at the base of mountains.
5.
The broken fragments of rock are called scree or talus
(S) These loose pieces of rock accumulate at the base of steep slopes.
(D) On mountains like Croagh Patrick, large scree slopes are visible as a result of freeze-thaw action.
(SE) These rock fragments contribute to the characteristic landscape in high-altitude regions.
7.
Freeze-thaw action is a type of mechanical weathering
(S) This process breaks rocks down physically, without changing their chemical structure.
(D) It is especially effective in high-altitude regions where temperature fluctuations are common.
(SE) Mechanical weathering like freeze-thaw action plays a vital role in the breakdown of rock material.
8.
Diagram of freeze-thaw weathering:
A labelled diagram can illustrate how water enters cracks, freezes, expands, and causes the rock to fracture.
Chemical Weathering: Carbonation (7 SRPs)
1.
Carbonation is a type of chemical weathering
(S) Carbon dioxide from the atmosphere dissolves in rainwater to form weak carbonic acid.
(D) This acid reacts with calcium carbonate in limestone, causing it to dissolve.
(SE) This process plays a key role in breaking down limestone in regions like the Burren in Ireland.
2.
The chemical reaction between carbonic acid and calcium carbonate breaks down limestone
(S) The reaction forms calcium bicarbonate, which is easily washed away by rainwater.
(D) This gradually erodes the limestone over time.
(SE) This results in the formation of distinctive karst landscapes.
3.
Carbonation is most effective in areas with high rainfall
(S) The Burren in Co. Clare, which experiences frequent rainfall, is an ideal location for carbonation.
(D) The rainfall accelerates the weathering process.
(SE) Over time, carbonation contributes to significant landscape changes in these areas.
4.
Carbonation enlarges the joints and bedding planes in limestone
(S) The acid seeps into cracks, dissolving the rock and widening the fissures.
(D) This process forms landforms like limestone pavements.
(SE) Such features are characteristic of karst landscapes, where carbonation has been extensive.
5.
Limestone is particularly susceptible to carbonation because it is made of calcium carbonate
(S) Calcium carbonate reacts readily with carbonic acid, making limestone more prone to chemical weathering.
(D) Other rocks are less affected due to their different compositions.
(SE) This explains why areas rich in limestone, like the Burren, are particularly vulnerable to this process.
6.
Carbonation contributes to karst landscape formation
(S) The Burren, with its characteristic clints, grikes, and underground caves, is an example of a karst landscape shaped by carbonation.
(D) These features are typical of limestone areas.
(SE) The landscape of the Burren is a prime example of how carbonation transforms the earth's surface.
7.
Diagram of carbonation:
A relevant diagram is necessary to get full 30 marks. Ensure it has a title, a frame and label. Keep it simple, don't waste time, it is only worth 2 marks.
Chemical Weathering and the Surface Karst Landscape
Carbonation is the primary type of chemical weathering that shapes karst landscapes
(S) Carbonation occurs when carbon dioxide from the atmosphere dissolves in rainwater, forming weak carbonic acid.
(D) This acid reacts with limestone and shapes the landscape.
(SE) The Burren in Ireland is an example of a landscape formed through this process.
The carbonic acid reacts with calcium carbonate in limestone
(S) The reaction forms calcium bicarbonate, which is soluble in water and easily washed away.
(D) This process gradually dissolves and breaks down the limestone, shaping the landscape over time.
(SE) Limestone pavements are created as a result.
Carbonation is particularly effective in areas with high rainfall
(S) In places like the Burren in Co. Clare, where there is frequent rain, carbonation significantly accelerates the weathering process.
(D) Rain increases the rate of dissolution.
(SE) This makes the Burren an ideal location for karst landscape formation.
Surface karst landscapes are characterised by features such as limestone pavements
(S) Limestone pavements form when overlying soil or rock is eroded.
(D) This exposes the limestone beneath, leading to its weathering.
(SE) Features like clints and grikes are formed as a result.
Clints and grikes are the defining features of a limestone pavement
(S) Clints are flat blocks of limestone, while grikes are the deep fissures between them.
(D) These fissures are formed by the widening of joints through carbonation.
(SE) This creates the characteristic blocky appearance of limestone pavements.
Grikes are created by the process of carbonation
(S) Rainwater, made slightly acidic by carbon dioxide, seeps into the joints in the limestone.
(D) Over time, this dissolves the limestone along these joints, widening them into grikes.
(SE) This forms the fissures seen in karst landscapes like the Burren.
Clints are the remaining blocks of limestone between the grikes
(S) These blocks are gradually eroded by carbonation.
(D) This contributes to the distinctive pattern of limestone pavements.
(SE) Over time, the landscape is altered by the process.
Limestone pavements are typical features of karst landscapes
(S) They are common in areas with exposed limestone, such as the Burren.
(D) These pavements are shaped by thousands of years of carbonation.
(SE) The landscape continues to evolve under the influence of weathering.
The permeability of limestone aids the formation of limestone pavements
(S) Water easily seeps through the joints and bedding planes in limestone.
(D) This speeds up the weathering process.
(SE) This leads to the formation of clints and grikes, which define karst landscapes.
In karst regions, carbonation can also lead to the formation of swallow holes
(S) Swallow holes form when surface water enters a joint or crack in the limestone.
(D) Gradually, the rock is dissolved, creating an underground passage.
(SE) These passages are common in karst areas and contribute to underground drainage.
Swallow holes are important in the development of dry valleys
(S) Over time, as rivers disappear underground through swallow holes, they leave dry valleys on the surface.
(D) This is a typical feature of karst landscapes.
(SE) Dry valleys are evidence of past river flow that now travels underground.
Surface karst features like clints, grikes, and swallow holes are all products of carbonation
(S) The acidic rainwater dissolves the limestone and gradually transforms the landscape into unique karst terrain.
(D) These features are common in areas such as the Burren.
(SE) The Burren’s landscape is a testament to the power of chemical weathering.
The Burren in Co. Clare is an example of a surface karst landscape shaped by carbonation
(S) The flat limestone pavement, characterised by clints and grikes, was exposed through a combination of glacial activity and chemical weathering.
(D) This landscape showcases the effects of carbonation over thousands of years.
(SE) The Burren remains a striking example of a karst landscape in Ireland.
Diagram of a limestone pavement and carbonation process:
A relevant diagram is necessary to get full 30 marks. Ensure it has a title, a frame and label. Keep it simple, don't waste time, it is only worth 2 marks.
Surface & Underground Features
You could be asked about the formation of surface features only, or underground features only, or as a combination question, so learn limestone pavements for surface, and limestone pillar for underground. I suggest learning pillar, as you can talk about stalactites and stalagmites during this process, which will give you lots to write about.
Formation of a Limestone Pavement
1.
Sedimentary structures such as bedding planes and joints play a key role in shaping landforms
(S) Bedding planes are the horizontal layers of sedimentary rock, while joints are vertical cracks in these layers.
(D) These structures influence how rocks weather and erode.
(SE) This affects the landscape’s development.
2.
Bedding planes are formed as sediments are deposited in layers
(S) These horizontal planes separate different layers of sediment, with each layer representing a period of deposition.
(D) Over time, the compaction and lithification of sediments turn these layers into solid rock, like limestone or sandstone.
(SE) This leads to the formation of distinct landforms.
3.
Joints are vertical cracks that occur as sedimentary rocks undergo stress
(S) These cracks form due to tectonic forces or the drying and shrinking of sediments during lithification.
(D) Joints increase the permeability of the rock.
(SE) This makes the rock more susceptible to weathering.
4.
Limestone formations, such as the Burren in Co. Clare, are characterised by distinct bedding planes and joints
(S) In limestone pavements, bedding planes and joints form patterns of clints and grikes, where the joints widen due to carbonation.
(D) The acid dissolves the limestone, widening the joints.
(SE) This creates the characteristic blocky landscape of limestone pavements.
5.
Bedding planes control how water flows through rock layers
(S) Water travels along these planes, leading to selective erosion.
(D) This process is particularly evident in karst landscapes, where water seeps through bedding planes.
(SE) This results in the formation of underground caves and swallow holes.
6.
In karst regions, joints provide pathways for water to infiltrate the rock
(S) Rainwater, which is slightly acidic, reacts with the calcium carbonate in limestone along joints and bedding planes.
(D) The acidic water dissolves the rock.
(SE) This forms distinctive landforms such as swallow holes and caves.
7.
Clints and grikes in limestone pavements are formed along joints
(S) Grikes are widened joints that develop as acidic rainwater dissolves the limestone, while clints are the remaining blocks of limestone between the grikes.
(D) As the joints widen, the characteristic patterns form.
(SE) These features define karst landscapes like the Burren.
8.
The permeability of joints allows for the formation of caves in sedimentary rock
(S) As water infiltrates through joints, it gradually dissolves the rock along these cracks.
(D) Over time, the cracks widen into caves.
(SE) This can create large underground cave systems like Aillwee Cave in the Burren.
9.
In sandstone landscapes, joints and bedding planes also play a significant role in landform development
(S) Sandstone contains both bedding planes and joints that guide weathering processes.
(D) The erosion along these features shapes the landscape.
(SE) This has contributed to the formation of the Munster Ridge and Valley Province in Ireland.
10.
The erosion of sedimentary rock is often concentrated along bedding planes
(S) In coastal environments, wave action exploits these planes, causing the rock to erode in horizontal layers.
(D) This leads to the formation of cliffs and wave-cut platforms.
(SE) Bedding planes play a key role in the development of these coastal features.
11.
Joints also affect how sedimentary rocks respond to mechanical weathering
(S) In cold climates, freeze-thaw action can cause water in joints to freeze and expand.
(D) This widens the cracks and leads to the breakdown of the rock.
(SE) This process shapes mountain landscapes, such as those seen in Croagh Patrick.
12.
Sedimentary structures are vital in the development of valley and ridge landscapes
(S) Sedimentary rocks erode along bedding planes and joints, with softer rock layers weathering more quickly than harder layers.
(D) This creates alternating valleys and ridges.
(SE) The Munster Ridge and Valley Province is an example of this landscape.
13.
Swallow holes and dry valleys in karst landscapes are shaped by the presence of joints
(S) As water moves through the joints, it dissolves the rock and creates underground drainage systems.
(D) Over time, rivers disappear underground.
(SE) This leaves behind dry valleys on the surface.
14.
The exposure of sedimentary structures to chemical weathering further shapes the landscape
(S) Carbonation, the chemical reaction between rainwater and calcium carbonate in limestone, primarily occurs along joints and bedding planes.
(D) This leads to the gradual breakdown of the rock.
(SE) The formation of karst features is heavily influenced by this weathering process.
15.
Diagram of sedimentary structures A relevant diagram is necessary to get full 30 marks. Ensure it has a title, a frame and label. Keep it simple, don't waste time, it is only worth 2 marks.
Formation of a Limestone Pillar
Formation of a Limestone Pillar
Carbonation is the primary process involved in the formation of limestone pillars
(S) This chemical weathering process occurs when carbon dioxide from the atmosphere dissolves in rainwater to form weak carbonic acid.
(D) The acid reacts with calcium carbonate in limestone, dissolving it.
(SE) This shapes the landscape by creating caves and underground features.
Limestone pillars are found underground in caves
(S) Caves are created by carbonation, which dissolves the limestone and enlarges underground passages.
(D) Over time, this process creates large caverns.
(SE) Limestone pillars form in these caverns.
The process begins with the formation of stalactites on the ceiling of caves
(S) Water containing dissolved calcium carbonate drips from the ceiling, leaving behind tiny deposits of calcite.
(D) These deposits build up over time.
(SE) This forms long, hanging features known as stalactites.
Stalagmites form on the cave floor beneath the stalactites
(S) Calcite-laden water drops from the stalactite and hits the cave floor, depositing calcite.
(D) These deposits grow upwards over time.
(SE) This creates stalagmites.
Over time, the stalactites and stalagmites grow towards each other
(S) When they eventually meet, they form a limestone pillar or column that connects the cave floor and ceiling.
(D) The pillar becomes a solid structure within the cave.
(SE) It is a prominent feature of karst caves.
The rate of pillar formation depends on the amount of water dripping and the concentration of calcium carbonate
(S) In areas with heavy rainfall, such as the Burren, more calcite is deposited as water drips frequently.
(D) This speeds up the rate of pillar formation.
(SE) The more water that drips, the faster the pillar grows.
Limestone pillars are common in karst landscapes such as the Burren in Co. Clare
(S) The Burren’s caves, including Aillwee Cave, contain many examples of these features.
(D) The dissolution of limestone over thousands of years creates these pillars.
(SE) Carbonation plays a key role in their formation.
In karst caves, carbonation continues to enlarge the joints and bedding planes in the limestone
(S) This allows more water to flow through the rock, which sustains the formation of stalactites, stalagmites, and pillars.
(D) Water flow ensures that these features continue to grow.
(SE) As long as water drips through the cave system, the pillars will develop.
The formation of caves and underground landforms is influenced by the permeability of limestone
(S) Water easily seeps through joints and bedding planes, dissolving the limestone.
(D) This process enlarges underground caverns.
(SE) It allows features like limestone pillars to form continuously.
Limestone pillars are examples of deposition rather than erosion
(S) Carbonation erodes the limestone to create the caves, but the pillars form through the deposition of calcite.
(D) Calcite is deposited as water drips onto cave floors.
(SE) This demonstrates how both deposition and erosion shape karst landscapes.
Stalagmites tend to be thicker and shorter than stalactites
(S) Water spreads out more when it hits the cave floor, leading to wider deposits of calcite.
(D) This difference in deposition shapes stalagmites differently from stalactites.
(SE) The distinction between stalagmites and stalactites is a key feature of cave systems.
Limestone pillars are unique to karst landscapes
(S) These landforms develop in regions where limestone is the dominant rock and carbonation is active.
(D) The Burren in Ireland is an example of such a landscape.
(SE) Extensive underground cave systems in these areas contain many limestone pillars.
Stalagmites and stalactites take thousands of years to form, making limestone pillars an indicator of the age of the cave system
(S) The older the cave, the larger and more developed the pillars tend to be.
(D) This slow process demonstrates the long-term development of karst landscapes.
(SE) Large limestone pillars can indicate the age and maturity of a cave system.
Diagram of limestone pillar formation
A relevant diagram is necessary to get full 30 marks. Ensure it has a title, a frame and label. Keep it simple, don't waste time, it is only worth 2 marks.
