Flashcards in Water On The Land Deck (30)
What is the long profile?
Shows how the gradient changes of the different courses of a river.
What is the cross profile?
Shows what the cross section of a river looks like.
Characteristics of the upper course?
Steep, v-shaped valley, steep sides, narrow, shallow channel.
Characteristics of the middle course?
Medium gradient, gently sloping valley sides, wider, deeper channel.
Characteristics of the lower course?
Gentle gradient, very wide, almost flat valley, deep channel.
What do vertical and lateral erosion change?
The cross profile of a river.
What does vertical erosion do to the cross profile of a river?
It deepens the river valley and channel, making it v-shaped. It's dominant in the upper course of a river.
What does lateral erosion do to the cross profile of a river?
It widens the river valley and channel. It's dominant in the middle and lower courses.
What are the four processes of erosion?
What is hydraulic action?
When the force of the water breaks rock particles away from the river channel.
What is abrasion?
When eroded rocks picked up by the river scrape and rub against the channel, wearing it away. Most erosion happens by abrasion.
What is attrition?
When eroded rocks picked up by the river smash into each other and break into smaller fragments. Their edges also get rounded off as the rub together.
What is solution?
When river water dissolves some types of rock. E.g. Chalk and limestone.
What are the four processes of transportation?
What is traction?
When large particles like boulders are pushed along the river bed by the force of the water.
What is saltation?
When pebble-sized particles are bouncing along the river bed by the force of the water.
What is suspension?
When small particles like silt and clay are carried along by the water.
What is solution?
When soluble materials dissolve in the water and are carried along.
What is deposition?
When a river drops eroded material.
Why does deposition occur?
When a river slows down.
What are the reasons for a river slowing down?
The volume of water in it falls.
The amount of eroded material in the water increases.
The water is shallower - the inside of a bend.
The river reaches it's mouth.
How are channels and valleys formed?
Rivers form channels and valleys as they flow downhill. They erode the landscape, then transport the material to somewhere else as it is deposited.
When a rivers eroding and depositing material it can form?
Meanders and ox-bow lakes.
Where are meanders formed?
In the middle and lower courses.
How and why material is deposited on the outside of a bend?
The current is faster on the outside of the bend because the river channel is deeper. Less friction to slow the water down. More erosion takes place on the outside of the bend forming river cliffs.
How and why is material deposited on the inside of the bend?
The current is slower on the inside of the bend because the river channel is shallower. There's more friction to slow the water down. Material is deposited on the inside, forming slip - off slopes.
How are ox-bow lakes formed?
When meanders get larger.
Erosion causes the outside bends to get closer until there's only a bit of small land left. The river breaks through this land during a flood so the river flows along the shortest course. Deposition eventually cuts off the meander forming and ox-bow lake.
How are waterfalls formed?
Form where a river flows over an area of hard rock followed by an area of softer rock. The softer rock is eroded more creating a step in the river. The water goes over the step and erodes it more and more.
How is the plunge pool formed?
When the hard rock is eventually undercut by erosion. It becomes unsupported and collapses. The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion. Therefore creating a plunge pool.