In this weeks lessons we will be investigating what is the nature of weathering and mass movement? By the end of today’s lesson you will be able to describe and explain: Physical weathering. The formation of scree slopes

Weathering is the disintegration and decomposition of rocks in situ. Weathering unlike erosion, does not involve the movement of material. Rewrite the above sentence changing the words in bold for more simple terms. So that a Year 8 pupils would understand it.

Weathering is the breaking up and decay of rocks in their place of origin. Weathering unlike erosion, does not involve the movement of material

Physical Weathering is the disintegration of rocks into smaller pieces by physical processes without any change in the chemical composition of the rock. It is most likely to occur in areas of bare rock where there is no vegetation to protect the rock from extremes of weather. 1.Draw two sketches one of a cliff side where physical weathering will take place and one where physical weathering will not.

This is an example of physical weathering which occurs in cold climates where temperatures move above and below freezing point and the exposed rock contains many cracks.

Water enters the cracks during the day. During the colder night the water turns to ice, expands and exerts pressure on the surrounding rock. When temperatures rise, the ice melts and the pressure is released. Repeated freezing and thawing widens the cracks and causes pieces of rock to break off.

Scree slopes are made of the loose, sharp rocks, which have fallen down a cliff (scree) due to the process of weathering. They often fall down a narrow gully, to form a fan shape at the foot of the cliff. As the material is weathered by freeze-thaw it falls on top of the existing scree and so the scree slopes gradually becomes higher and spreads further out into the valley.

1.Describe the scree slope in Figure 15.8 on p246 of ‘The New Wider World’. 2.Copy the diagram opposite and add labels to your diagram to show how a scree slopes develops as a result of freeze-thaw.

In desert areas rocks heat up quickly during the day and the outer layers expand. At night, the temperature drops considerably and the outer layers contract. The continual contraction and expansion of the outer layers of the rock break the outer layer into pieces. This process is called EXFOLIATION or ONION- SKIN WEATHERING. The pieces of broken rock are called SCREE.