Weathering And The River Valley Flashcards
What is weathering?
The breakdown of rocks where they are
How are rocks in a drainage basin broken down?
Weathering
What are the main types of weathering?
Mechanical, chemical and biological
What is mechanical weathering?
The breakdown of rock without changing its chemical composition
Freeze-thaw weathering = mechanical weathering. What happens?
Temperature alternates above and below 0
Water gets into cracks in rock
Water freezes and expands - pressure
Water thaws and contracts - releases pressure
Repeated freezing and thawing - cracks widen - rock breaks
What is chemical weathering?
Breakdown of rock by changing its chemical composition
Carbonation weathering = chemical weathering. What happens?
Rain water contains CO2 - weak carbonic acid - reacts with rock that contains calcium carbonate - rocks dissolved by rainwater
What is biological weathering?
Breakdown of rocks by living things
An example of biological weathering
Plant roots grow into cracks and push cracks apart - rock breaks
What is the path of a river as it flows downhill called?
Course
The upper course is closest to the…
Source of the river
The middle and lower course are closest to the…
Mouth of the river
Rivers flow in channels…
In valleys
What do rivers do?
Erode landscape - wear it down
Transport material to somewhere else - then deposit it
What causes the shape of the valley and channel to change along the river?
Erosion or deposition - whichever has the most impact
What does the long profile of a river show?
How the gradient changes over different courses
What does the cross profile of a river show?
What a cross-section of the river looks like
What is the upper course gradient and valley and channel shape like?
Gradient - steep
Valley shape - v shaped, steep sides
Channel shape - narrow and shallow
What is the middle course gradient and valley and channel shape like?
Gradient - medium
Valley shape - gently sloping
Channel sides - wider and deeper
What is the lower course gradient and valley and channel shape like?
Gradient - gentle
Valley shape - very wide, almost flat
Channel shape - very wide, deep
