1. Upper Course Landforms Flashcards
What is Cap Rock?
A layer of hard rock underlaid by a layer of softer rock
Cap rock plays a crucial role in the formation of various geological features.
Define Gorge.
A steep-sided valley downstream of a waterfall
Gorges are often formed by the erosional processes of rivers.
What is differentiated erosion?
Differences in the rate of erosion due to differences in rock resistance
This process leads to the formation of various landforms.
What is a Plunge Pool?
A deep basin shape where water pools below a waterfall
Plunge pools are critical in the erosion process of waterfalls.
Define Overhang in the context of waterfalls.
A ledge of cap rock caused by the plunge pool undercutting it
Overhangs can eventually collapse due to erosion.
What does Undercut refer to?
The cave-like feature eroded behind the waterfall
Undercutting is a significant part of the waterfall formation process.
What energy transformation occurs in the upper course of a river?
Gravitational potential energy is converted into kinetic energy
This transformation enables the river to erode its channel effectively.
Describe the typical landscape features found in the upper course of a river.
V-shaped valleys, waterfalls and interlocking spurs
These features result from the river’s erosion and the resistance of different rock types.
What are interlocking spurs?
Sections of the valley that the river bends around
They form as a result of more resistant rock.
What is vertical erosion?
The process where the river erodes downwards into the channel
Vertical erosion is responsible for creating features like steps, rapids, and potholes.
What is hydraulic action?
The force of the water that presses air into cracks
This process contributes to the erosion of river beds.
Define abrasion in the context of river erosion.
The sandpaper effect of load on the bed
Abrasion is a key erosional process that shapes river landforms.
What is solution in terms of erosion?
The dissolving of minerals
This process contributes to the overall erosion and landscape shaping.
What is the sequence of waterfall formation?
Differentiated erosion leads to the formation of a plunge pool, undercutting the cap rock, creating an overhang that collapses
This process occurs over hundreds of years.
True or False: The waterfall increases in height and retreats upstream over thousands of years.
True
This process is a result of continuous erosion.
Fill in the blank: Waterfalls form in the upper course of the river due to _______.
[differentiated erosion]
This process is essential for understanding river landform development.
What happens to the plunge pool over time?
It deepens further due to the force of water
This deepening contributes to the overall erosion and waterfall formation.
Model Response: Explain and describe the formation of waterfalls (4)
Waterfalls form in the upper course of the river due to differentiated erosion. Softer layers of rock underlying a harder layer are vertically eroded. Processes such as hydraulic action (the force of the water that presses air into cracks), abrasion (the sandpaper effect of load on the bed) and solution (the dissolving of minerals) combine over hundreds of years to form a deep plunge pool. Over time the force of the water deepens the plunge pool further and it undercuts the hard cap rock above. This creates an overhang that eventually is left unstable and collapses. Hard angular rock further deepens the plunge pool through abrasion and the waterfall increases in height and retreats upstream. Over thousands of years, this leaves a steep steep-sided downstream.
