River Processes - Erosion, Transportation & Deposition | AQA GCSE 9-1 Geography

Summary

This script delves into the intricate processes of river erosion, distinguishing between vertical and lateral erosion. It explains four erosional processes: hydraulic action, ablation, attrition, and solution, highlighting how water's force and chemistry shape riverbeds and banks. The script also covers four types of sediment transportation: suspension, saltation, traction, and solution, detailing how sediment moves differently based on its size and the river's energy. Finally, it touches on the deposition of sediment when the river's energy wanes, typically at the mouth or where water volume decreases.

Takeaways

• 🌊 Erosion in rivers is categorized into vertical and lateral erosion, with vertical erosion occurring downwards and lateral erosion occurring sideways.
• 💧 Hydraulic action is the primary erosional process in rivers, where the shear force of water impacts the riverbed and banks.
• 🔍 Air becomes trapped in cracks and crevices, causing the banks to break apart due to the pressure of water.
• 🏞 Ablation is the process where the load carried by the river is hit against the bed or banks, leading to erosion.
• 🌌 Attrition is the process where rocks carried by the river hit against each other, becoming smaller and rounder.
• 🍂 Solution is the process where slightly acidic river water flows over rocks like limestone or chalk, dissolving them.
• 🚰 There are four types of sediment transportation in rivers: suspension, saltation, traction, and solution.
• 🌀 Suspension is the transportation of the lightest sediment within the water, common in the lower course.
• 🏖 Saltation involves larger pebbles that are bounced along the riverbed, too heavy to be suspended.
• 🛤 Traction is the rolling of even larger pebbles along the riverbed, common in the upper course.
• 🏝 Solution transportation involves the dissolving of soluble particles into the river.
• 🗺 Deposition is the process where river sediment is dropped, occurring when the river loses energy and velocity, typically at the mouth or where water volume decreases.

Q & A

What is the process of wearing away of the riverbed and banks in rivers called?

The process is called erosion, which can be categorized into vertical and lateral erosion.

What are the two main types of erosion that occur in rivers?

The two main types of erosion are vertical erosion, which occurs downwards, and lateral erosion, which occurs sideways.

What is hydraulic action in the context of river erosion?

Hydraulic action refers to the shear force of the water hitting the riverbed and banks, causing erosion.

How does air contribute to the erosion of river banks?

Air becomes trapped in cracks and crevices in the banks, and when it expands, it causes the banks to break apart, contributing to erosion.

What is ablation in the context of river erosion?

Ablation is when the load being carried by the river is hit against the bed or banks, causing erosion.

What is attrition in the process of river erosion?

Attrition occurs when rocks being carried by the river are hit against each other, making them smaller and rounder.

What is solution in the context of river erosion?

Solution happens when slightly acidic river water flows over rocks such as limestone or chalk, dissolving them.

What is suspension in the process of river sediment transportation?

Suspension is the transportation of the lightest sediment, which is carried within the water, and it is most common in the lower course of the river.

What is the difference between suspension and saltation in river sediment transportation?

Suspension involves the lightest sediment being carried within the water, while saltation involves larger pebbles being bounced along the riverbed.

What is traction in the context of river sediment transportation?

Traction is when even larger pebbles that are too heavy to be picked up are rolled along the riverbed, and it is most common in the upper course.

What is the position where river sediment is typically dropped?

River sediment is typically dropped when the river loses energy and velocity, often in shallow water at the mouth or where water volume decreases.