Weathering and Erosion
National Curriculum (information shown in red):
To understand, through the use of detailed place-based exemplars at a variety of scales, the key processes in physical geography relating to rocks and weathering.
GCSE (information shown in green):
AQA (A):
- Rocks are susceptible to weathering. The type of weathering that is most effective is determined by the composition of the rock and the climate.
- Mechanical weathering – freeze thaw weathering and exfoliation. Chemical weathering – solution, carbonation. Biological weathering.
- Different rocks create contrasting landforms and landscapes – a study of granite; chalk and clay and Carboniferous limestone.
AQA (B):
- Weathering and erosion are important physical processes in coastal areas.
- Describe and explain the processes of weathering and erosion that affect coastal environments.
OCR (B):
- Understand how physical processes of weathering can change coastlines and river basins.
- How weathering, erosion, transport and deposition operate in a river basin.
- How weathering, erosion, transport and deposition operate along constructive and destructive coastlines.
Edexcel (A):
- The impact of weathering, erosion and mass movement on the coast
- The impact of weathering, erosion and mass movement on river landscapes.
A-Level (information shown in blue):
OCR:
- Weathering, erosion, transportation and deposition give rise to distinctive types of coastal landform and river features.
- The study of a river basin and costal area, including practical research and out-of-classroom work – fieldwork, to illustrate: the processes responsible for distinctive features, including weathering, mass movement, erosion and deposition.
To understand, through the use of detailed place-based exemplars at a variety of scales, the key processes in physical geography relating to rocks and weathering.
GCSE (information shown in green):
AQA (A):
- Rocks are susceptible to weathering. The type of weathering that is most effective is determined by the composition of the rock and the climate.
- Mechanical weathering – freeze thaw weathering and exfoliation. Chemical weathering – solution, carbonation. Biological weathering.
- Different rocks create contrasting landforms and landscapes – a study of granite; chalk and clay and Carboniferous limestone.
AQA (B):
- Weathering and erosion are important physical processes in coastal areas.
- Describe and explain the processes of weathering and erosion that affect coastal environments.
OCR (B):
- Understand how physical processes of weathering can change coastlines and river basins.
- How weathering, erosion, transport and deposition operate in a river basin.
- How weathering, erosion, transport and deposition operate along constructive and destructive coastlines.
Edexcel (A):
- The impact of weathering, erosion and mass movement on the coast
- The impact of weathering, erosion and mass movement on river landscapes.
A-Level (information shown in blue):
OCR:
- Weathering, erosion, transportation and deposition give rise to distinctive types of coastal landform and river features.
- The study of a river basin and costal area, including practical research and out-of-classroom work – fieldwork, to illustrate: the processes responsible for distinctive features, including weathering, mass movement, erosion and deposition.
Subject knowledge:
Weathering involves the breakdown of rocks on the earth's surface. There are three types of weathering: physical, chemical and biological.
- Physical: changed by physical factors such as temperature.
- Chemical: chemicals in the rain react with the rock and cause it to weather.
- Biological: caused by plants and animals burying in the rock.
Physical (mechanical) weathering: Physical weathering is caused by physical changes such as changes in temperature, freezing and thawing, and the effects of wind, rain and waves. There are two main types of physical weathering: Freeze-thaw weathering and onion-skin weathering.
1) Freeze-thaw weathering takes place when water is trapped in the cracks of a rock and freezes.If the air temperature drops below freezing, the water will freeze and expand by 9-10 per cent putting pressure on the rock which then expands and enlarges the cracks. The process of freeze-thaw weathering occurs until the rock is weakened and shattered. It is most effective where the temperature fluctuates around 0°C, eg on north-facing high altitude slopes in Snowdonia.
Weathering involves the breakdown of rocks on the earth's surface. There are three types of weathering: physical, chemical and biological.
- Physical: changed by physical factors such as temperature.
- Chemical: chemicals in the rain react with the rock and cause it to weather.
- Biological: caused by plants and animals burying in the rock.
Physical (mechanical) weathering: Physical weathering is caused by physical changes such as changes in temperature, freezing and thawing, and the effects of wind, rain and waves. There are two main types of physical weathering: Freeze-thaw weathering and onion-skin weathering.
1) Freeze-thaw weathering takes place when water is trapped in the cracks of a rock and freezes.If the air temperature drops below freezing, the water will freeze and expand by 9-10 per cent putting pressure on the rock which then expands and enlarges the cracks. The process of freeze-thaw weathering occurs until the rock is weakened and shattered. It is most effective where the temperature fluctuates around 0°C, eg on north-facing high altitude slopes in Snowdonia.
2) Onion-skin weathering takes place in hot desert climates. During the heart of the day the surface of the rocks heats up and expands. At night it is cold and the rocks contract. This causes this layers of the rock to peel off (much like an onion). Using an actual onion could help students visualise this weathering method.
Examples of rocks weathered by physical weathering:
Chemical Weathering:
This occurs when weak acids in rainwater attack and break down rock surfaces. Some types of rock are easily weathered by chemicals. When acidic rainwater falls on limestone or chalk, a chemical reaction occurs and the rock is weathered.
1) Limestone solution (Carbonation):
Limestone consists of calcium carbonate. When carbon dioxide is dissolved in rainwater, it makes a weak acid known as carbonic acid. When carbonic acid comes into contact with limestone and passes through joints, it reacts with the rock to form calcium bicarbonate. This is soluble and is carried away in solution, gradually weathering the limestone.
Acid rain makes chemical weathering happen more quickly. Buildings and statues made from rock are damaged as a result. This is worse when the rock is limestone rather than granite. Acid rain also kills trees and fish.
Examples of chemical weathering:
This occurs when weak acids in rainwater attack and break down rock surfaces. Some types of rock are easily weathered by chemicals. When acidic rainwater falls on limestone or chalk, a chemical reaction occurs and the rock is weathered.
1) Limestone solution (Carbonation):
Limestone consists of calcium carbonate. When carbon dioxide is dissolved in rainwater, it makes a weak acid known as carbonic acid. When carbonic acid comes into contact with limestone and passes through joints, it reacts with the rock to form calcium bicarbonate. This is soluble and is carried away in solution, gradually weathering the limestone.
Acid rain makes chemical weathering happen more quickly. Buildings and statues made from rock are damaged as a result. This is worse when the rock is limestone rather than granite. Acid rain also kills trees and fish.
Examples of chemical weathering:
The central image demonstrates that it is not just natural scenery that is shaped by weathering. Weathering and erosion can affect buildings, statues, roads and pavements too.
Chemical weathering can be visible in many places. Dunstanburgh Castle in Northumberland is a fantastic example of this in the UK.
Biological Weathering:
This involves both plants and animals. For example, burrowing animals such as rabbits can burrow into a crack in a rock, making it bigger and splitting the rock. Plant seeds can begin to grow in the cracks of a rock. As the roots expand, the cracks in the rock expands, the rock weakens and pieces break off. Paths can become damaged because of all the boots and shoes wearing them away. Therefore this is biological weathering caused by human activity.
Once rocks have been broken down they may be eroded or transported. Erosion is the wearing away of the land by water, ice or wind. This is common in the drainage basin of the river and the coastline.
While all of the information is highlighted in green, it is important to note that KS3 requires a basic understanding of all of this information (including definitions and impacts).
Chemical weathering can be visible in many places. Dunstanburgh Castle in Northumberland is a fantastic example of this in the UK.
Biological Weathering:
This involves both plants and animals. For example, burrowing animals such as rabbits can burrow into a crack in a rock, making it bigger and splitting the rock. Plant seeds can begin to grow in the cracks of a rock. As the roots expand, the cracks in the rock expands, the rock weakens and pieces break off. Paths can become damaged because of all the boots and shoes wearing them away. Therefore this is biological weathering caused by human activity.
Once rocks have been broken down they may be eroded or transported. Erosion is the wearing away of the land by water, ice or wind. This is common in the drainage basin of the river and the coastline.
While all of the information is highlighted in green, it is important to note that KS3 requires a basic understanding of all of this information (including definitions and impacts).
Erosion:
There are four main processes of erosion: - Hydraulic action- The force of the water breaking rock particles away from the river channel. - Abrasion- Eroded rocks picked up by the river scrape and rub against the channel wearing it away. Most erosion happens by abrasion. - Attrition- Eroded rocks picked up by the river smash into each other and break into smaller fragments. Their edges also get rounded off as they rub together. - Solution- River water dissolves some types of rock, e.g. chalk and limestone. |
Rocks and landscapes:
Granite landscapes have Tors and Moorland: Granite has lots of cracks which aren't evenly spread. This allows freeze-thaw and chemical weathering to wear down parts of the rock quickly due to the amount of cracks for water to get into. Sections of granite that have fewer joints are weathered more slowly than the surrounding rocks and stick out at the surface forming tors. Granite is also impermeable (doesn't let water through) which creates moorlands- these are large areas of waterlogged and acidic soils with low-growing vegetation. An example of this is in Dartmoor which attracts tourists.
Chalk and clay landscapes have escapements and vales: Horizontal layers of chalk and clay are sometimes titled slightly by earth movements. Clay is less resistant than chalk so is eroded faster. The chalk is left sticking out forming escarpments (hills). Where the clay has been eroded it forms vales- wide areas of flat land.
Granite landscapes have Tors and Moorland: Granite has lots of cracks which aren't evenly spread. This allows freeze-thaw and chemical weathering to wear down parts of the rock quickly due to the amount of cracks for water to get into. Sections of granite that have fewer joints are weathered more slowly than the surrounding rocks and stick out at the surface forming tors. Granite is also impermeable (doesn't let water through) which creates moorlands- these are large areas of waterlogged and acidic soils with low-growing vegetation. An example of this is in Dartmoor which attracts tourists.
Chalk and clay landscapes have escapements and vales: Horizontal layers of chalk and clay are sometimes titled slightly by earth movements. Clay is less resistant than chalk so is eroded faster. The chalk is left sticking out forming escarpments (hills). Where the clay has been eroded it forms vales- wide areas of flat land.
Rivers:
Erosion can be vertical or lateral- both types happen at the same time, but one is usually dominant over the other at different points along the river. Vertical erosion deepens the river valley (and channel), making it V-Shaped. Its dominant in the upper course of the river. Lateral erosion widens the river valley (And channel). It's dominant in the middle and lower courses. The faster the river is flowing, the more erosion happens (see diagram to the right). |
Coasts:
The coastline is weathered and eroded to create different landscapes. The waves that carry out erosional processes are called destructive waves; these have a high frequency and are high and steep. These occur on destructive coastlines. Erosion by waves form many coastal landforms over long periods of time. An example of this are caves, arches, stacks and stumps.
Headlands can be eroded to from caves, arches, stacks and stumps. Headlands are usually made up of resistant rocks that have weaknesses like cracks. Waves crash into the headlands and enlarge the cracks- mainly be hydraulic power and abrasion. Repeated erosion and enlargement of the cracks causes a cave to form. Continued erosion deepens the cave until it breaks through the headland- forming an arch. Erosion continues to wear away the rock supporting the arch until it eventually collapses. This forms a stack. The stack is eventually worn away to give it a stump which can be covered by the water at high tide.
The coastline is weathered and eroded to create different landscapes. The waves that carry out erosional processes are called destructive waves; these have a high frequency and are high and steep. These occur on destructive coastlines. Erosion by waves form many coastal landforms over long periods of time. An example of this are caves, arches, stacks and stumps.
Headlands can be eroded to from caves, arches, stacks and stumps. Headlands are usually made up of resistant rocks that have weaknesses like cracks. Waves crash into the headlands and enlarge the cracks- mainly be hydraulic power and abrasion. Repeated erosion and enlargement of the cracks causes a cave to form. Continued erosion deepens the cave until it breaks through the headland- forming an arch. Erosion continues to wear away the rock supporting the arch until it eventually collapses. This forms a stack. The stack is eventually worn away to give it a stump which can be covered by the water at high tide.
Case study: coastal management in Holderness (would also be useful for GCSE coast topic)
The Holderness coast is in the north east of England. This is one of the most vulnerable coastlines in the world and it retreats at a rate of one to two metres every year. The problem is caused by: - Strong prevailing winds creating longshore drift that moves material south along the coastline. - The cliffs are made of a soft boulder clay. It will therefore erode quickly, especially when saturated. The village of Mappleton, perched on a cliff top on the Holderness coast, has approximately 50 properties. Due to the erosion of the cliffs, the village is under threat. In 1991, the decision was taken to protect Mappleton. A coastal management scheme costing £2 million was introduced involving two types of hard engineering - placing rock armour along the base of the cliff and building two rock groynes. - Mappleton and the cliffs are no longer at great risk from erosion. - The rock groynes have stopped beach material being moved south from Mappleton along the coast. However, this has increased erosion south of Mappleton. Benefits in one area might have a negative effect on another. The increased threat of sea level rise due to climate change, means that other places will need to consider the sustainability of coastal defence strategies for the future. VIDEO: http://www.bbc.co.uk/learningzone/clips/a-farm-is-threatened-by-coastal-erosion-at-holderness-east-yorkshire/3189.html |
For A-Level classes students would be required to use the information as well as using fieldwork techniques to show the changed. This could include a trip to the Welsh coast (see picture to the left) or a closer location that includes the required coastal or river features.
Fieldwork could include: - Photographs - Field sketch - GIS - Talks withs council/ coastal protection agencies - Questionnaires for local people - Measuring the basin of a river |
Teaching and pedagogy:
Starter activity at the beginning of the topic: Individually create a mind map of what you already know about rocks and weathering. For example, any names of rock types, types of weathering, weathering landforms. At the end of each lesson you shall add what you have learned. This will become a useful tool for revision.
KS3 CLASS (could also be adapted to fit a GCSE class)
Aim: To be able to explain the processes of weathering
Objectives:
a) To be able to identify the different effects of weathering processes.
b) To be able to explain how physical, chemical and biological weathering can alter rocks.
c) To be able to effectively use key terminology in the explanation of weathering processes.
Starter:
Match the following rock to its type of weathering. Once complete, write your own definition of each type.
Starter activity at the beginning of the topic: Individually create a mind map of what you already know about rocks and weathering. For example, any names of rock types, types of weathering, weathering landforms. At the end of each lesson you shall add what you have learned. This will become a useful tool for revision.
KS3 CLASS (could also be adapted to fit a GCSE class)
Aim: To be able to explain the processes of weathering
Objectives:
a) To be able to identify the different effects of weathering processes.
b) To be able to explain how physical, chemical and biological weathering can alter rocks.
c) To be able to effectively use key terminology in the explanation of weathering processes.
Starter:
Match the following rock to its type of weathering. Once complete, write your own definition of each type.
Main activity:
Create a cartoon strip of physical, chemical or biological weathering. More able students may be able to go onto creating a diary entry of this rock's life.
Plenary:
Using 3 post it notes, write a key word associated with each type of weathering. Stick them on the board under the correct process.
Resources:
- Powerpoint with images
- A3 paper
- Coloured pens
- post it notes
GCSE CLASS:
Aim: To create an in depth case study of a coastal region affected by weathering
Objectives:
a) To be able to label coastal landforms created by weathering.
b) To be able to explain how coastal landforms have been created.
c) To be able to understand the impacts of coastal weathering on a specific location.
Starter:
Using the play doh on your table, create a model of a cave, arch, stack and stump.
Main activity:
Create a case study of coastal weathering occurring in a specific location. Explain what type of weathering is occurring and describe how the process happens. Discuss any impacts this is having on the area. Remember to use images and diagrams.
Plenary:
On an exit card, write down 2 important facts about the area you have studies and 1 fact about your partner's.
Resources:
- Play doh
- Laptops/ iPads/ Computers
- Exit cards
- Handouts (differentiated task if students require help with the main activity)
A-LEVEL CLASS:
Aim: To start preparing for fieldwork on coastal weathering
Objectives:
a) To be able to list different techniques for managing coastal weathering and erosion.
b) To be able to create an in-depth case study profile on [name of area visiting]
c) To create questions to investigate when at [name of area visiting]
Starter:
As a class start to list as many different coastal management techniques. Starting at one end of the class, write down one technique and pass it on. Done in silence.
Main activity:
Using the available resources, create a profile on the area we will be visiting. You should include information on its location, how the coast is used by tourists, any strategies in place to manage the coast, satellite images etc. (pupils could be given a sheet of sections to fill out if they are struggling with the activity)
Plenary:
On a post-it note, write down one question that you would like to find out when visiting [name of are visiting].
Homework:
- Plan an answer to the following exam question:
Explain how to prevent weathering and erosion in coastal regions and what players would be involved in the decision making (10 marks)
- Consider what information you will need to find out to be able to answer the following question relating it to [area visiting]
Looking specifically at a coastal region, explain the impacts of weathering and erosion (8 marks)
Resources:
- laptops/ iPads/ computer room
- Worksheets (if required)
- Post-it notes
Create a cartoon strip of physical, chemical or biological weathering. More able students may be able to go onto creating a diary entry of this rock's life.
Plenary:
Using 3 post it notes, write a key word associated with each type of weathering. Stick them on the board under the correct process.
Resources:
- Powerpoint with images
- A3 paper
- Coloured pens
- post it notes
GCSE CLASS:
Aim: To create an in depth case study of a coastal region affected by weathering
Objectives:
a) To be able to label coastal landforms created by weathering.
b) To be able to explain how coastal landforms have been created.
c) To be able to understand the impacts of coastal weathering on a specific location.
Starter:
Using the play doh on your table, create a model of a cave, arch, stack and stump.
Main activity:
Create a case study of coastal weathering occurring in a specific location. Explain what type of weathering is occurring and describe how the process happens. Discuss any impacts this is having on the area. Remember to use images and diagrams.
Plenary:
On an exit card, write down 2 important facts about the area you have studies and 1 fact about your partner's.
Resources:
- Play doh
- Laptops/ iPads/ Computers
- Exit cards
- Handouts (differentiated task if students require help with the main activity)
A-LEVEL CLASS:
Aim: To start preparing for fieldwork on coastal weathering
Objectives:
a) To be able to list different techniques for managing coastal weathering and erosion.
b) To be able to create an in-depth case study profile on [name of area visiting]
c) To create questions to investigate when at [name of area visiting]
Starter:
As a class start to list as many different coastal management techniques. Starting at one end of the class, write down one technique and pass it on. Done in silence.
Main activity:
Using the available resources, create a profile on the area we will be visiting. You should include information on its location, how the coast is used by tourists, any strategies in place to manage the coast, satellite images etc. (pupils could be given a sheet of sections to fill out if they are struggling with the activity)
Plenary:
On a post-it note, write down one question that you would like to find out when visiting [name of are visiting].
Homework:
- Plan an answer to the following exam question:
Explain how to prevent weathering and erosion in coastal regions and what players would be involved in the decision making (10 marks)
- Consider what information you will need to find out to be able to answer the following question relating it to [area visiting]
Looking specifically at a coastal region, explain the impacts of weathering and erosion (8 marks)
Resources:
- laptops/ iPads/ computer room
- Worksheets (if required)
- Post-it notes
Exam questions:
Higher: a) Describe the process of chemical weathering (4 marks). b) Using a specific case study, explain the impacts of weathering and erosion (8 marks). Foundation: a) Explain the difference between weathering and erosion (4 marks) b) Describe the different types of weathering (8 marks) |
A-Level: a) Looking specifically at a coastal region, explain the impacts of weathering and erosion (8 marks). b) Explain how to prevent weathering and erosion in coastal regions and what players would be involved in the decision making (10 marks) |