Flashcards in 1.3-River landscapes Deck (50)
What are 2 physical processes that shape a river?
weathering and mass movement
What are the 3 types of weathering?
What is biological weathering?
Roots growing and animals burrowing into cracks in rocks causing them to split apart.
What is chemical weathering?
slightly acidic rainwater dissolves rocks
What is mechanical weathering?
freeze thaw action
What is the process of freeze thaw action?
water fills a crack
water freezes and the crack widens
repeated action increases the size of the crack
loose blocks if rocks are called scree
What are 2 processes of mass movement?
sliding and slumping
What is sliding?
where rock or material moves down a slope under the influence of gravity
what is slumping?
Where the river erodes the bottom of the valley slope causing the rock to become saturated and slump/collapse, making the slope steeper.
What does slumping cause?
material to slide downwards particularly if it's saturated with rainwater
What is hydraulic action?
where the force of the water of the bed and banks removes material
What is attrittion?
the load that is carried by the river bumps together and wears down into smoother pieces
what is solution?
some minerals dissolving in river water
What is abrasion?
material carried by the river rubs against the bed and banks
What are the 4 main types or river transportation?
What is it when large boulders are rolled along the river bed?
What is it when smaller pebbles are bounced along the river bed?
What is it when finer sand and silt particles are carried along in the flow?
What is it called when some minerals are dissolved in the water and carried along in the flow?
What shows how a river changes from source to mouth?
The Bradshaw model
what are charectaristics of the upper course of rhe river?
narrow steep sides
What are some charectaristics characteristics of the middle course?
flatter channel shape
What are some charectaristics of the lower course of a river?
very large discharge
What features are formed in the upper course?
What features are formed in the lower course?
ox bow lakes
What features are formed in the middle course?
What increases the frequency of storms?
more periods of heavy rain and overflowing rivers
What increases the risk of flooding?
frequency of storms
periods of hot dry weather
soil becoming inpermeable during cold conditions
how are waterfalls formed?
The soft rock erodes more quickly, undercutting the hard rock.
The hard rock is left overhanging and because it isn’t supported, it eventually collapses.
The fallen rocks crash into the plunge pool. They swirl around, causing more erosion.
Over time, this process is repeated and the waterfall moves upstream.
A steep-sided gorge is formed as the waterfall retreats.