Limestone Uplands

Higher GeographyPhysical Environments: Lithosphere

Limestone Uplands Outline

1. Characteristics and location of carboniferous limestone in the British Isles.

2. Formation of limestone landforms on the surface.

3. Formation of limestone landforms beneath the surface.

4. Identifying limestone landforms on O.S. Maps.

Aims of the lesson

• To learn about the characteristics of carboniferous limestone and where it is found in the UK.

• To be able to describe the formation of a limestone pavement using diagrams.

Limestone

Limestone is a sedimentary rock.

It is created when sediments containing large amounts of dead sea creatures are turned into rock.

Contains large amounts of calcium carbonate (CaCO3).

Karst Landscapes

Carboniferous limestone creates distinctive landscapes called Karst.

The main Karst areas of the British Isles are:– Midland Scotland– South Wales– Yorkshire Dales– The Burren, Ireland

Yorkshire Dales

The Burren

Brecon Beacons, South Wales

Factors Influencing Karst Scenery

1. Rock Structure– the rock is divided into

blocks as a result of breaks between the rock beds (bedding planes) and vertical cracks (joints).

2. Permeability– water passes easily

through the rock by following the bedding planes and joints.

3. Carbonation & Solution

bedding plane

joint

Permeability

Carbonation

Limestone = Calcium CarbonateRainwater = Carbonic Acid

Carbonic Acid dissolves Calcium Carbonate

This is called CARBONATION, a type of solution weathering.

Or … H2O + CO2= H2CO3

CaCO3 + H2CO3 = Ca(HCO3)2Calcium Carbonate Dilute Carbonic Acid Calcium

Hydrogen Carbonate

Karstic Landforms

Limestone Pavement

One of the most obvious features of an upland limestone landscape.

Limestone is exposed to weathering by glacial erosion.

Diagram Memory Activity

On the front desk is a series of diagrams showing the formation of a limestone feature.

One person at a time from each group will come up to the front and study the diagrams.

He/she will then report back to the group. By the end of the activity you should all have an exact copy of this diagram in your notes.

Limestone Pavements

1. Limestone is exposed to weathering by glacial erosion.2. Carbonation and freeze thaw weathering exploit cracks in

the rock called joints and bedding planes.

3. These gaps are widened until a series of rectangular blocks is created. This is the limestone pavement. The blocks are called clints and the joints are called grykes.

Limestone Pavements

Clint

Clint

ClintClint

Clint

Gryke

Gryke

Gryke

E.g. Malham Cove, Yorkshire Dales

Summary

So far we have learnt:1. Limestone is a sedimentary rock that contains large amounts

of calcium carbonate (CaCO3).2. Carboniferous limestone forms karst landscapes in the British

Isles e.g. Yorkshire Dales, The Burren, Brecon Beacons.3. Limestone is made up of blocks separated by joints and

bedding planes.4. Limestone is permeable – water can pass through it.5. Limestone is vulnerable to chemical weathering – carbonation.6. A major surface karst landform is the limestone pavement e.g.

Malham Cove.

Revision Question

With the aid of annotated diagrams, explain the formation of a limestone pavement. (6 marks)

Use you notes & p111 of the P&H Environments textbook to help you (diagram on p114).

Tips: • Ensure you include a fully annotated

diagram• Include the processes involved e.g.

explain the process of carbonation and freeze-thaw.

• Ensure your written answer is well structured and takes the reader through the formation process step by step.

1. Limestone exposed to surface by glacial erosion.

2. Structure of limestone.3. Processes of chemical & physical

weathering.4. How is limestone changed?5. Named example.

Sample Answer: Limestone PavementLimestone pavements are a karstic landform made from carboniferous limestone. This sedimentary rock formed 350 million years ago and contains a high quantity of the calcium carbonate (1). A limestone pavement begins to form when a glacier erodes the topsoil and exposes the limestone beneath to the surface (1). At this point it is vulnerable to attack from both chemical and physical weathering processes.Weak carbonic acid is created when carbon dioxide mixes with water in clouds (1). This acid rain falls onto the limestone and exploits natural breaks in the rock called joints and bedding planes (1). Over time the acid rain dissolves the limestone and widens the gap between the joints (1). This process is called carbonation (1). Eventually the surface is divided into a series of rectangular blocks called clints separated by gaps called grykes (1).Freeze-thaw weathering can also contribute to the formation of this landform (1). Rainwater falls into the vertical joints and then freezes during cold nights (1). Once it freezes the water expands by 10% and exerts pressure on the sides of the rock, widening them over time (1).An example of this landform is Malham Cove in the Yorkshire Dales (1).

Sample Answer: Limestone PavementLimestone pavements are a karstic landform made from carboniferous limestone. This sedimentary rock formed 350 million years ago and contains a high quantity of the calcium carbonate (1). A limestone pavement begins to form when a glacier erodes the topsoil and exposes the limestone beneath to the surface (1). At this point it is vulnerable to attack from both chemical and physical weathering processes.Weak carbonic acid is created when carbon dioxide mixes with water in clouds (1). This acid rain falls onto the limestone and exploits natural breaks in the rock called joints and bedding planes (1). Over time the acid rain dissolves the limestone and widens the gap between the joints (1). This process is called carbonation (1). Eventually the surface is divided into a series of rectangular blocks called clints separated by gaps called grykes (1).Freeze-thaw weathering can also contribute to the formation of this landform (1). Rainwater falls into the vertical joints and then freezes during cold nights (1). Once it freezes the water expands by 10% and exerts pressure on the sides of the rock, widening them over time (1).An example of this landform is Malham Cove in the Yorkshire Dales (1).

Mark Your Work

Using the sample answer you have been given, mark your own work out of 6 marks.

Any points you have not included should be added as bullet points beneath your original answer.

Aims of the lesson

1. We will be able to describe the formation of a shake hole.

2. We will be able to describe the formation of a pothole and give a named example.

Shakeholes

A shakehole is a depression in the limestone landscape. In some limestone areas there is a covering of boulder clay about two or three metres thick. Shakeholes are formed where surface water washes the boulder clay away. They are usually found in groups.

Potholes (Sink Holes or Swallow Holes)

Surface and rain water do not flow far on exposed limestone, but infiltrate rapidly into the rock and soil. A stream travelling over an impermeable rock will very quickly disappear when it has to travel over limestone. These potholes can be many metres deep leading down to a series of subsurface features.Pothole Formation

Pothole

Pothole

Gaping Gill: Second largest pothole in the UK

Review Questions

1. What is the difference between a shakehole and a sink hole?

2. What sort of type of material is found blocking a shakehole and how is it removed?

3. What is our named example of a pothole?

4. What factors could lead to a pothole growing in size?

Summary

In this lesson we have:• Learnt that a shakehole is formed when

boulder clay deposited in a limestone hollow (doline) is removed by rivers.

• Learnt that a pothole is created by a river flowing over permeable limestone and flowing underground e.g. Gaping Gill.

Aims of the lesson

To carry out your own research on the following landforms:

1. Shakeholes2. Potholes3. Scars & Scree Slopes4. Dry Valley5. Gorge

Glaciokarstic Features

BBC Website Research

Go to the following website: http://www.bbc.co.uk/scotland/education/int/geog/limestone/index.shtml

Collect information in your notes on:1. What is a glaciokarstic feature?2. Shakeholes, Potholes, Scars & Scree Slopes,

Dry Valley, Gorge.a) How was the feature formed?b) Named example of landforms.

Glaciokarstic Features

That glaciokarstic landforms have been influenced by both limestone and glacial processes.

Scars & Scree Slopes

During the last ice age huge ice sheets scraped away the soil covered spurs in many valleys in the Yorkshire Dales. Steep cliffs of bare rock were exposed. Because these scars are more liable to frost shattering and other forms of erosion they usually have scree slopes of broken rock below them.

Dry Valleys

During the last ice age the limestone was frozen to great depths. When the ice melted it carved out valleys over the frozen rock. When the limestone thawed out the surface water was able to infiltrate down through the rocks and the dry valleys were left with no surface water.

Gorge

During the meltwater phase of the last ice age, underground streams eroded vast caverns as huge volumes of water travelled through the limestone. Sometimes the roofs of these caverns can collapse exposing the "underground stream" in a very steep sided gorge

Summary

So far we have learnt:– That glaciokarstic landforms have been influenced

by both limestone and glacial processes.– Examples of glaciokarstic landforms:• Scars & Scree Slopes e.g. Twistleton Scar or Raven Scar• Dry Valley• Gorge Trow Gill Gorge

ODD ONE OUT

Sedimentary Igneous Metamorphic

Carbonation Exfoliation Freeze-thaw

Soil Creep Rockfall Landslide

Dry Valley Pothole Shakehole

The Burren Yorkshire Dales Loch Lomond

Aims of the lesson

• We will be able to describe the formation of a cavern.

• We will be able to describe the formation of a stalactite, stalagmite and pillar.

Limestone Landforms Beneath the Surface

Underground Landforms

Caverns & Caves

Water dissolves the rock.

River flows down pot-hole

Joints & bedding planesclose together.

Caverns & Caves

Limestone dissolvedby the water to forma cavern

Limestone Pillar

Stalagmites

Stalactites

Cavern Formation

River flows down pot-hole and works its way through the joints and bedding planes.This water is still acidic and so dissolves the limestone by carbonation.Where the joints and bedding planes are close together, the limestone may be completely worn away to form a cavern.

Stalactites, Stalagmites & Pillars

Sequencing ActivityRead p113 of the P&H textbook.

In your groups, read the statements on the next slide carefully.

As a group try to decide what order you would put the cards into to describe the formation of stalactites, stalagmites & pillars.

Stalactites, Stalagmites & Pillars1. Water that has worked its way through joints & bedding planes enters the cavern and

comes into contact with air. This causes it to lose some CO2 and become less acidic.

2. This less acidic water cannot hold onto as much of the dissolved calcium hydrogen-carbonate.

3. As water drips down from the cavern roof some of it evaporates. This leaves some calcium carbonate behind, which is deposited on the roof.

4. These deposits build up over time to form finger like growths pointing downwards called stalactites. Some calcium carbonate also evaporates on the cavern floor forming a stalagmite.

5. These are known as dripstone features that grow at a rate of around 7mm every year. If the two connect, this forms a pillar. Excellent examples of these features are found in the Ingleborough Caves.

Stalactites, Stalagmites & Pillars

Water containing CaCO3

CaCO3deposited

CaCO3Deposits build up over time

Stalactite

Stalagmite

Pillar

REMEMBER!

Stalactites grow down from the cavern roof.

Stalagmites grow up from the cavern floor.

Stalactites, Stalagmites & Pillars

• http://www.youtube.com/watch?v=IKZ9EHewjZg

Review Questions

Describe and explain the formation of stalactite, stalagmites and pillars (dripstone features). You may wish to use diagrams in your answer. (6 marks)

Structure:• Water moving through limestone – cavern formed.• Water enters cavern – loses CO2 .

• Calcium carbonate deposits build up.• Finger like growth coming down from ceiling.• Deposits build up on cavern floor.• Eventually connect.• Named example – Ingleborough Caves

Sample Answer: Stalactites, Stalagmites & Pillars

Water that has worked its way through joints & bedding planes present in the limestone enters a cavern and comes into contact with air (1). This causes it to lose some CO2 and become less acidic (1).

This less acidic water cannot hold onto as much of the dissolved calcium hydrogen-carbonate (1). As water drips down from the cavern roof some of the calcium carbonate evaporates and is deposited on the roof of the cavern (1).

These deposits build up over time to form finger like growths pointing downwards called stalactites (1). Some calcium carbonate also evaporates on the cavern floor forming a stalagmite (1).

These are known as dripstone features that grow at a rate of around 7mm every year (1). If the two connect, this forms a pillar (1). Excellent examples of these features are found in the Ingleborough Caves of the Yorkshire Dales(1).

Sample Answer: Stalactites, Stalagmites & Pillars

Water that has worked its way through joints & bedding planes present in the limestone enters a cavern and comes into contact with air (1). This causes it to lose some CO2 and become less acidic (1).

This less acidic water cannot hold onto as much of the dissolved calcium hydrogen-carbonate (1). As water drips down from the cavern roof some of the calcium carbonate evaporates and is deposited on the roof of the cavern (1).

These deposits build up over time to form finger like growths pointing downwards called stalactites (1). Some calcium carbonate also evaporates on the cavern floor forming a stalagmite (1).

These are known as dripstone features that grow at a rate of around 7mm every year (1). If the two connect, this forms a pillar (1). Excellent examples of these features are found in the Ingleborough Caves of the Yorkshire Dales(1).

Summary

Today we have learnt…

– How to describe the formation of a cave.

– How to describe the formation of stalactites, stalagmites and pillars, with reference to named examples.

On the Wall

Using the post-its on your desk, stick your answers to each question on the wall.Fastest Team Wins!1. What speed do stalactites grow on average?2. What is our named example of:– Limestone Pavement– Cave– Pothole

3. Describe the process of carbonation on limestone.4. Name the 3 important characteristics of limestone.5. What is the name given to a river that reappears from

underground?

Aims of the lesson

• To give feedback on your progress so far.

• To describe the formation of gours in limestone caverns.

Gours

• These are ridges of calcium carbonate formed on cave floors.

• Formed as CO2 is lost from streams flowing along the surface.

• Calcium carbonate is deposited.

Evaluation

On lined paper answer the following questions:1. Why did you choose Higher Geography?2. What grade are you hoping to gain?3. How do you prefer to learn? Discussion?

Activities? PPQ? Notes from the board?4. Is there anything you would change about

the way your are learning in Geography?

Geography Pictionary

RULES:

– One person per group will come up to the board and be given a word.

– Draw images to get your team to guess the word.

– Drawer cannot talk or write words!

What we have learnt so far…

Types of rock

Physical & Chemical Weathering Processes

Mass Movement

What we have learnt so far…

Characteristics of carboniferous limestone

Surface Features

Underground Features

Tell me someone who…

1. Can name all 3 types of rock.2. Knows the difference between erosion and

weathering.3. Can name 2 types of physical weathering.4. Can name 2 types of chemical weathering.5. Can name 3 factors that influence mass movement.6. Can name a process of mass movement.7. Can list 3 factors that influence karst scenery.8. Can give a named example of a limestone pavement.9. Can describe what a glaciokarstic landform is.

Aims of the lesson

• To revise the content that we learnt before the holidays.

Group Answer

Working in your groups, you are going to create the perfect answer to one of the questions on the whiteboard.

Before writing your answers, you should agree upon a plan that you must show to me.

Use the resources on your tables to help you.

Questions

1. Describe and explain the formation of stalactite, stalagmites and pillars (dripstone features). You must use diagrams in your answer. (6 marks)

2. With the aid of annotated diagrams, explain the formation of a limestone pavement. (6 marks)

3. Describe and explain the conditions and processes which encourage the formation of scree slopes. (6 marks)

Peer Marking

Pass your answer to another table.

You must now give another groups question a mark out of 6.

Use your sample answers & textbooks to help you.

Summary

So far we have…

• Revised what we have learnt in Higher Geography so far.

Identifying Limestone Landforms on OS maps

Identifying landforms on an OS map is one of the key skills you will need to develop.

There will be questions based on this in your exam.

Lesson Aim: To learn how to identify limestone landforms on an OS map.

OS Map Questions

You could be asked to look at the map and recognise the evidence of limestone features.

You may also be asked to explain how these features have formed.

You must use grid references (6 figure) and only refer to what you can see on the map.

What can you see?

Swallow Hole

Limestone PavementLimestone Scar

Resurgence Points

Activity

Turn to p112 in the Higher Textbook.

Study the map extract of Ingleborough.

Describe the evidence that suggests that Ingleborough is an area of Carboniferous Limestone. (8 marks)

Tips: • Identify various

features shown on the map and ensure you name them and provide grid references

• You can also make general comments about the area that suggests it is limestone.

Extension

Choose one of the carboniferous limestone features you mentioned in Q1, and with the aid of annotated diagrams, explain its formation. (6 marks)

Summary

So far we have…– Learnt how to recognise limestone landforms on

O.S Maps.

– Practiced how to answer O.S. Map PPQs.