  LO: To compare the different types of weathering  Can you locate any of the images below? What has happened to the rock formations? Weathering

 Types of Weathering  Rocks are different shapes and sizes because they are changed by the conditions in their environment  Rocks gradually wear away – this is known as weathering  There are three types of weathering: - 1.Physical weathering 2.Chemical weathering 3.Biological weathering

  Biological weathering Watch the demos of physical and chemical weathering

 Physical Weathering Freezing and thawing

 Physical Weathering temperaturefreezing and thawingwindrain waves  Physical weathering is caused by changes such as changes in temperature, freezing and thawing, and the effects of wind, rain and waves…  Temperature  Temperature - when a rock gets hot it expands a little, and when a rock gets cold it contracts a little. If a rock is heated and cooled many times, cracks form and pieces of rock fall away (this type of physical weathering happens a lot in deserts, because it is very hot during the day but very cold at night)

 Physical Weathering  Wind rain waves wind  Wind, rain and waves – the wind can blow tiny grains of sand against a rock wearing the rock away and weathering it F The rain can lash against a rock and wear it away F Waves F Waves can crash against a rock and wear it away

 Chemical Weathering Chemical weathering

 Chemical Weathering  Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it chemical weathering  Minerals in rocks may react with the rainwater, causing the rock to be weathered – this is chemical weathering  Some types of rock are easily weathered by chemicals, such as limestone and chalk  Some types of rock are not easily weathered by chemicals, such as granite and gabbro

 Chemical Weathering  The burning of fossil fuels produces oxides of sulphur and nitrogen, causing rain to become more acidic (acid rain)  This type of acid rain reacts more quickly with rock minerals, weathering them more rapidly…

 Biological Weathering

 biological weathering  Animals and plants can wear away rocks – this is biological weathering  Burrowing animals such as rabbits can burrow into a crack in a rock, making it bigger and splitting the rock F Plant roots can grow in cracks – as they grow bigger, the roots push open the cracks and make them wider and deeper, eventually causing pieces of rock to fall away F People can cause biological weathering by walking. Over time, paths in the countryside become damaged due to the boots wearing them away

  Produce a cartoon strip to describe (L5) and explain (L6) the different types of weathering

Safety check Jake works at a outdoor adventure centre. The centre closes in October for winter and reopens at the end of March. Jake must check to see if the mountain bike trail and rock climbs are safe before the centre reopens. These photos were taken last October just before the rock climbing faces were closed to the public. Predict whether each rock face will still be safe to climb after the winter months. Explain the reasons for your prediction. You should include in your explanation: The type of weathering that could have affected the rocks to make the face dangerous. Evidence from the weather data opposite that helps to explain why this would have happened during the months between October and March. How the weathered rock from the walls would be eroded. Weather data He decides that it may need to be closed down for repairs. Use ideas about weathering and erosion, as well as the weather data below, to explain why Jake is concerned. Jake takes a photo to record the state of the bridge that runs across the river. The bridge is attached to rocks on the river bank. MonthMinimum temperature  C Maximum temperature  C Rainfall cm* October November December January February March *Rainfall has been much higher than normal this year. Extension

L5 predicts that on the first rock climb pieces of rock may have either fallen off or be loose dues to freeze–thaw weathering suggests that the low temperatures would mean that the rocks on the climbing faces would have been weathered this process is a type of physical weathering. L6 As Above: predicts that the smooth crack-free surface of the second rock climb should mean that it will not have undergone freeze–thaw weathering as there were not places for water to gather and then freeze explains that water in the cracks in the rock expanded as it froze. This process would take place during the winter months when temperatures were below zero the rocks from the climbing walls could have been eroded by wind or gravity Jake is concerned about the bridge because it is attached to rocks on the river bank that may have been weathered and eroded over the winter.

Plenary Saving our castles This castle is built on top of basalt rock. The basalt formed inside a volcano. Over millions of years the rock around it has been eroded away until only the hard basalt is left. This castle is built near the edge of a cliff. At beach level the cliff is formed from soft clay and silt. Above this are layers of stronger sandstones and grit. The sea defences around Portland Harbour, which were built in 1903, have reduced wave height in the area. The last stonework from the castle fell 50 years ago. Many organisations are involved in preserving our historic castles but looking after these ancient buildings costs money. It is important to prioritise any work carried out. Read the information about the three castles shown below and list them in order of priority for preservation work. You should consider both the long-term stability of the castle structures and the safety of people visiting the sites. Explain your order by using the ideas of weathering and erosion. This castle is built from soft silt stone. The site is still in its natural state with plants such as ivy growing over the walls. Castle 3: Edinburgh Castle Castle 2: Sandsfoot Castle, Dorset Castle 1: Wigmore Castle, Hereford and Worcester