EROSION

What is Erosion? Erosion is the removal and breaking down of soil and rock from the Earths surface by natural processes The movement of weathered material from one point to another is known as erosion

As pieces of rock are moved , ATTRITION & ABRASION ATTRITION As pieces of rock are moved , they knock against each other and are broken down into smaller pieces . This process is called attrition

ABRASION As these small pieces of rock are moved across the surface , the rocks become smoother or they cut into the surface , this process is known as abrasion

The forces that cause rock to break up : Agents of erosion Flowing Rivers Sea Moving Ice Wind

DIFFERENCE BETWEEN WEATHERING , EROSION AND DEPOSITION Weathering is the process of breaking up a rock into smaller pieces . During this process the smaller pieces of rock remain at the point they have been weathered and are not moved . Erosion is the process by which the weathered material is moved, and the rock breaks down further while being moved. Deposition is the putting down or dropping of smaller rock pieces to make new landforms.

RIVERS – FEATURES OF EROSION AND DEPOSITION ALONG A RIVER COURSE

Rivers are one of the most important geographical landforms created, they are an interaction in both human and physical geography. In the river the processes of erosion and deposition occur. A river flows from it source, the point of its origin a high lying area with steep gradients eg. a mountain top, towards the mouth a low lying area with a rarely flat surface eg. a dam or the sea

The movement of water in a river occurs at different stages and can be at a fast moving speed or a generally slow speed or in between. As the river flows this force of water and pressure that exists moves the rock ,stone ,sand and other sediments along the river this is erosion occurring.

The three sections of a river The three sections of a river are called river courses and are described as : Upper course : A steep slope with a narrow valley Middle course : This has a medium slope and a wider valley Lower course : This has a gentle slope or is flat and a wide valley.

Features of the upper course Narrow v- shaped valley This part of the river has a lot of energy because of the steep slope. The energy is used to erode a steep and deep river channel . The river has lots of large rocks in the river bed.

Potholes Potholes are round deep holes found in the bed of a river , they are formed when a rock gets stuck in the bed of a river. The force of the water causes the rock to spin or turn . The turning of the rock is like a drilling action causing the rock to erode a round hole in the river bed forming a pothole .

Rapids and Waterfalls A rapid is formed when resistant rock in the river bed causes water to flow over and around the rocks .

Waterfall A resistant layer of rock does not erode easily A waterfall is formed when a hard or resistant rock layer in a river bed causes a steep slope or vertical drop. A resistant layer of rock does not erode easily

Subject Teacher : Social Studies IN THE NEXT LESSON We going to look at the features of the middle course and lower course We going to look at how the Sea and wave action acts as an agent of erosion. THANK YOU Compiled by : A Ellan Subject Teacher : Social Studies Geography