Diagram to follow
2. Describe the processes in the formation of a river gorge. (4)
As a river passes from a resistant rock onto less resistant rocks it is able to erode the river bed at a faster rate. This creates a steep in the river channel, increasing the velocity of the river at this point. The increased velocity adds to the erosive capacity of the river eroding a plunge pool at the step and deepening it into a waterfall. Undercutting of the resistant rock leads to its collapse allowing the waterfall to retreat upstream. This process is repeated and over thousands of years the upstream retreat creates a steep-sided channel, called a gorge, downstream of the waterfall.
3. Outline the processes of erosion that may occur within a river. (4)
Rivers may erode their bed, banks and sediment in several ways. Abrasion is the wearing away of rock by other rocks, as either the bedload or suspended load is moved by the water. Hydraulic action is the wearing away of rock by the sheer force of the moving water. Attrition is the breakdown of sediment via collisions with other moving sediment particles. Finally, solution is the dissolving and removal of soluble rocks by the water itself.
4. Describe the way that a river can transport its load. (4)
The load is the term used to describe the rocks moved within a river channel. Rivers can transport their load through four processes. Traction is the rolling or dragging of large bedload along the river bed, while saltation is the bouncing of sand grain along the bed. Suspension is the movement of fine silts and clays held in the water column while solution is the movement of ions dissolved in the river water.
2. Describe the processes in the formation of a river gorge. (4)
As a river passes from a resistant rock onto less resistant rocks it is able to erode the river bed at a faster rate. This creates a steep in the river channel, increasing the velocity of the river at this point. The increased velocity adds to the erosive capacity of the river eroding a plunge pool at the step and deepening it into a waterfall. Undercutting of the resistant rock leads to its collapse allowing the waterfall to retreat upstream. This process is repeated and over thousands of years the upstream retreat creates a steep-sided channel, called a gorge, downstream of the waterfall.
3. Outline the processes of erosion that may occur within a river. (4)
Rivers may erode their bed, banks and sediment in several ways. Abrasion is the wearing away of rock by other rocks, as either the bedload or suspended load is moved by the water. Hydraulic action is the wearing away of rock by the sheer force of the moving water. Attrition is the breakdown of sediment via collisions with other moving sediment particles. Finally, solution is the dissolving and removal of soluble rocks by the water itself.
4. Describe the way that a river can transport its load. (4)
The load is the term used to describe the rocks moved within a river channel. Rivers can transport their load through four processes. Traction is the rolling or dragging of large bedload along the river bed, while saltation is the bouncing of sand grain along the bed. Suspension is the movement of fine silts and clays held in the water column while solution is the movement of ions dissolved in the river water.
