Weathering PowerPoint PDF

# Weathering - Describe what chemical and physical weathering can do - Investigate how different rocks are affected by weathering ## What is weathering? Rocks are different shapes and sizes because they are changed by the conditions in their environment. The breakdown of rocks into smaller fragm...

# Weathering - Describe what chemical and physical weathering can do - Investigate how different rocks are affected by weathering ## What is weathering? Rocks are different shapes and sizes because they are changed by the conditions in their environment. The breakdown of rocks into smaller fragments is called **weathering**. Eventually the fragments become soil. Can you think of anything that could cause weathering? Rocks can be weathered by temperature change, water, frost and even plants and animals. ## Types of weathering There are three types of weathering: - physical weathering - biological weathering - chemical weathering. Which type of weathering is caused by each of these: - temperature change - acid rain - plants and animals? ## Rocks and Weathering **Contents** - Using rocks - Physical weathering - Biological weathering - Chemical weathering - After weathering - Summary activities ## Physical weathering Physical weathering occurs when rock is broken down into smaller pieces by the effects of temperature and water. - **Exfoliation weathering** (or 'onion-skin' weathering) is caused by very hot weather. - **Freeze-thaw weathering** is caused by the melting and freezing of water. Exfoliation and freeze-thaw weathering tend to occur in very different types of landscapes. Which type of weathering do you think will primarily occur in the desert, and which will occur in the mountains? ## Exfoliation weathering in action What is exfoliation weathering? Exfoliation weathering is the repeated heating and cooling of rock that causes the surface layers of the rock to flake off. Click "play" to find out more. ## Freeze-thaw weathering in action What is freeze-thaw weathering? During the freeze-thaw process, rocks exposed to the weather undergo physical changes and break apart. Click "play" to find out more. ## How can freezing water cause damage? You can see freeze-thaw weathering in action if you leave a bottle full of water in the freezer for too long. The water inside the bottle expands as it freezes. The ice that is formed creates huge forces on the bottle, which then cause it to break! Because water expands as it freezes it can create immense pressure in confined spaces. Does this explain why water pipes often burst in winter? ## Plants and weathering in action How does biological weathering work? Biological weathering is the disintegration of rock due to the actions of organisms such as bacteria, plants and animals. Click "play" to find out more. ## What is chemical weathering? **Slow chemical weathering** - Rainwater is naturally a weak acid because carbon dioxide in the air reacts with rainwater to form carbonic acid. - This weakly acidic rain reacts with minerals in rocks and slowly wears them away. **Rapid chemical weathering** - The burning of fossil fuels produces oxides of sulphur and nitrogen, which make rainwater more acidic. - Acid rain reacts quickly with minerals, so the rocks get weathered more rapidly. ## Examples of chemical weathering How has chemical weathering affected these rocks? ## Which type of weathering? Which type of weathering is likely in each situation? 1. A rock sitting on an alpine mountain 2. A seedling growing in the cracks between paving slabs 3. A rock sitting on a sand dune in the dessert 4. A mole digging a burrow 5. Acid rain falling on a headstone in a cemetery ## Test the different rocks to see how they are affected by weathering.