Weathering, Erosion and Distinctive Landscapes

1. Explain the terms weathering and erosion.

2. Name and describe the process of chemical and mechanical weathering

3. Describe and draw a limestone pavement

4. Describe surface and underground landforms of a karst landscape

5. Understand how this topic appears on the exam papers.

Mind Map: Weathering

• Lets do a mind map to remember what you learn from junior cert geography

Key words

• Denudation

• Mechanical weathering

• Chemical weathering

• Biological weathering

Denudation

This is all processes involved in the shaping of the earths crust

Denudation = weathering and erosion

Weathering• Weathering is the breaking down and

decay of rocks that are exposed to the weather

• There are three types1. Mechanical – Frost and temperature

changes2. Chemical – Rocks are dissolved3. Biological – Plants and animals

Erosion

• Erosion is the breaking down and removal of the rock.

• Three types of erosion• Moving water (rivers and sea)• Moving ice (Glaciation)• Moving air (wind)

Mechanical Weathering

• 3 Types

• Freeze Thaw Action

• Exfoliation

• Crystallisation of salts – When salts in a rock grow they can split the rock apart.

Mechanical WeatheringFreeze Thaw Action

• Weathering by frost is called freeze thaw action

In order for freeze thaw action to occur you need to have…

• Temperatures that rise above and fall below freezing (0°C)

• A good supply of water from rain, snow, sleet or hail.

Freeze Thaw Action

• http://www.absorblearning.com/media/attachment.action?quick=131&att=2799

• Where do you think this action usually occurs???

Mechanical Weathering - Exfoliation

• ‘Onion Peeling’

• Major contrasts in temperature

• Rises very high during the day and drop very low at night

• The change in temperature expands and contracts the rock causing the outer skin to shatter.

Class Activity

• Summarise the three types of mechanical weathering into your copies.

Biological Weathering

• Action of plants, animals and man can speed up mechanical and chemical weathering

Chemical Weathering Keywords

• Carbonation

• Oxidation

• Hydration

• Hydrolysis

Chemical Weathering

• Four types of chemical weathering1. Carbonation2. Oxidation3. Hydration4. Hydrolysis

Research the types of chemical weathering..Teach the class.

Distinctive Landscape

• Granite Landscape

• Limestone Pavement – Karst Landscape. Burren Co. Clare

Karst Keywords

• Burren• Tower Karst Landscape• Carbonation• Calcium Carbonate• Calcite• Limestone Pavement• Swallow Hole• Cavern• Dripstone Formations

Karst Region

• These are bare limestone regions

• Ireland’s best known Karst region the Burren in Co. Clare

• Burren = Rocky place (An Boireann)

• Soil in the area removed by Erosion

• International Example – Tower Karst Landscapes

The Burren

Surface and Underground Landforms

• Surface

Limestone Pavements

Swallow holes

• Underground

Caverns

Dripstone formations

The Burren

Limestone Pavement

Examples

• Near Black Head in the Burren Co. Clare

• Marble Arch Uplands in Co. Fermanagh

Revision… Limestone

• In your groups do a limestone revision mindmap…

• Remember the characteristics of limestone!!

Limestone Pavement Formation

• Limestone pavements from from the process of carbonation ‘All the Cs!’

1. Carbon dioxide in the air + rain = Weak Carbonic Acid.

2. Lands on limestone rock creating a chemical reaction.

3. Hydrogen in the carbonic acid separates the calcium carbonate (limestone) into calcium and bicarbonate atoms

4. These are soluble and are washed away… as a result the limestone is dissolved.

Limestone Pavement

• An exposed area of limestone

• Limestone is permeable. When rainwater falls onto the surface of the limestone it moves underground through joints and cracks in the rock.

• It has grikes and clints

• A Limestone Pavement is just like a bar of dairymilk chocolate!!

• Each group will be given a bar of chocolate…. I’d like you to describe the physical features of the bar of chocolate…

• DO NOT EAT IT!! WE NEED IT FOR THE REST OF THE CLASS!!

Clints

• These are the top flat pieces of the limestone.

• These are formed by chemical weathering dissolving away some of the rock landscape.

Clints

Grikes

• These are the joints or cracks between the Clints

• These have been formed by chemical weathering.

• Carbonic acid (acid rain) expands the width and depth of the cracks

Grikes

Class Activity• Read page 59 of your book.

Exam QuestionDescribe the formation of any one rock typeand how it produces a distinctive landscape.

- Describe the formation of limestone… notes from rock chaper

- Describe formation of a karst landscape and limestone pavements

- Use two examples Burren Co. Clare and Tower Karst Landscape (page 63)

Sinkholes/Swallow holes

An opening in the bed of the river through

which a river disappears underground in a

limestone region

Swallow Hole

Bedding Plane

Grikes

Class Activity: Sinkholes

• Read the formation of a sinkhole on page 60 of your book.

• Summarise the landforms in grouop

CAVE

Cavern

Animation of a Cavern

• http://www.classzone.com/books/earth_science/terc/content/visualizations/es1405/es1405page01.cfm

Activity: Read page 61

• Write out caverns into your own words into your copies

Dripstone formations

• Include stalactites, stalagmites, pillars, columns and curtains.

• Formed from the mineral calcite. Calcium carbonate in its purest form.

• Read page 62 in your book. Summarise into your own words.

Stalagmites

• When the drops of water fall to the floor and evaporate, they also deposit calcite. These deposits build up in a conical shape to form Stalagmites

Stalagmites

Stalactites

• When water containing dissolved calcium carbonate seeps through the rock, some drops hang from the roof of the cave/cavern for a while. Some of the water evaporates leaving behind deposits of calcite. These deposits build up over thousands of years and hang from the roof

to form Stalactites.

Stalactites

Pillar

• In time, the Stalactites and Stalagmites grow and join up to form pillars.

Pillar

• Prepare questions to suit both surface and underground.

Exam Questions: Could be asked for Underground or Surface Landforms

Weathering, Erosion and Distinctive Landscapes

1. Explain the terms weathering and erosion.

2. Name and describe the process of chemical and mechanical weathering

3. Describe and draw a limestone pavement

4. Describe surface and underground landforms of a karst landscape

5. Understand how this topic appears on the exam papers.