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Geography- C10-12
Erosion, Transportation and Deposition by Rivers, the Sea and Glaciers- Keywords
Term | Definition |
---|---|
Fluvial Erosion | Waterfall |
Waterfall | When a river flows over a vertical slope |
Flows over what area? | An area where hard rock lies on top of soft rock |
Which erodes faster? | Soft rock |
Why? | Through the fluvial erosional process of hydraulic action |
Hydraulic action | The power of the river hitting against the rock |
What is formed? | A vertical drop |
Where? | Where the hard rock and soft rock met |
Known as? | A waterfall |
What forms? | Plunge pool |
Where? | At the base |
Due to? | Hydraulic action and abrasion |
Abrasion | The river's load swirling around in the plunge pool, wearing away at the rock |
What happens to the rock above the plunge pool? | It is undercut and left hanging over the plunge pool |
What happens then? | The rock eventually collapses into the plunge pool |
Due to? | Hydraulic action and abrasion |
What happens to the process? | It repeats |
The waterfall does what | Gradually erodes its way upstream |
Example? | Powerscourt Waterfall, Co. Wicklow, or Torc Waterfall, Co. Kerry |
Fluvial Deposition | Levee |
Levee | A build-up of alluvium on the banks of a river |
Alluvium | Extremely fertile soil material deposited by rivers |
Feature of? | The old-stage river |
1st time | Low flow |
What happens? | Load is dropped onto the river bed |
What does this do? | Raises the height of the river bed |
2nd time | Flood |
What happens? | Water flows out more easily over the top of the channel and onto the surrounding land |
What happens the river on land? | Loses energy, deposits load |
What is deposited first, closer to the river? | The heavier, coarser material |
What is deposited further away from the river? | The finer material |
Where? | Flood plain |
3rd time | After many floods |
What is after happening? | The river builds up a bank on either side |
What is this called? | A levee |
Example? | Lower course of River Moy, Co. Mayo |
Sea Erosion | Sea cave, arch, stack and stump |
What kind of waves? | Destructive |
What do they attack | Weaknesses and cracks in the cliff |
Through what? | Hydraulic action, abrasion and compressed air |
Hydraulic action | The force of the water hitting off the rock |
Abrasion | The load of the sea hitting against the rock |
Compressed air | Air becomes trapped by incoming waves Puts pressure on the rock When water retreats, air expands back out and pressure drops suddenly Repeated, causing rock to weaken and shatter |
What happens to the cliff? | A cave forms |
What happens the cave? | It is widened further |
Through what? | The same erosion processes |
Until what? | The cave has been widened all the way through the headland |
What is this called? | An arch |
What happens then? | The arch is widened until the top of it collapses |
What is left? | A sea stack |
What happens the sea stack? | The same coastal erosion processes wear away the stack until it collapses into the sea |
What is left? | A sea stump |
Example | The Old Head of Kinsale, Co. Cork |
Sea transportation | Longshore Drift |
What materials? | Sand, silt, mud and pebbles |
What is this known as? | It's load |
Waves approach shore what way? | From the side |
Determined by what? | Prevailing wind |
What is prevailing wind? | The usual wind in an area |
What is Ireland's prevailing wind? | South westerly |
What force carries the waves up the shore? | Swash |
What force carries the waves back down the shore | Backwash |
At what angle does the swash carry the material back down the shore at? | A right angle |
What happens then? | The process is repeated |
In what pattern? | Zig-zag pattern |
Sea deposition | Beach |
Beach | A gently-sloping area of sand, shingle or stones that is found between high and low-tide levels |
Formed by what? | Longshore drift (swash and backwash movements of the waves) |
What kind of waves? | Constructive |
What happens to waves as they break? | They lose their energy |
What happens when this occurs? | The waves drop their load |
What carries it up the shore? | Swash |
What does the swash do then? | Deposit it |
Why is the backwash unable to carry all the material back out? | It is weaker than swash |
What is deposited first? | Heavier, coarser material |
What is carried closer to the shoreline by backwash? | Finer material |
What happens after this is repeated? | The material builds up |
What is formed? | A beach |
When are waves stronger? | During times of storms |
What are they able to do? | Carry material further up the shoreline |
To where? | The high-tide mark |
What happens to the material? | It is deposited |
What is now created | A storm beach |
Example? | Tramore, Co. Waterford |
Erosion by moving ice | Plucking and abrasion |
What occurs when ice goes over the ground? | Friction |
What is a result of this friction? | Heat |
What does this do the ice? | The ice at the bottom of the glacier is melted |
What is this called? | Meltwater |
Where does the meltwater go? | Into cracks in the rock |
What happens to the meltwater then? | It freezes when the temperature drops below 0 Degrees Celsius, sticking to the rock |
What happens when the glacier starts to move again? | The glacier plucks chunks of rock out of the ground, carrying them along with it at the base of the glacier |
What happens to the plucked rocks? | They become embedded in the base of the glacier |
What do these rocks do as the glacier moves on? | They abrade the surface over which they pass |
What does it mean to abrade? | To scrape and smooth |
Feature of Glacial Erosion | Glaciated valley/U-shaped valley |
Starts off as what? | V-shaped valley |
Definition | Originally a V-shaped valley that became straightened and deepened by a glacier filling it, making it look more u-shaped |
What glacial erosion processes occur? | Plucking and abrasion |
What is left behind after the glacier passes through? | A glaciated valley |
What changes are there to the V-shaped valley? | Flat valley floor Very steep sides |
Example | Glendalough, Co. Wicklow |
Glacial Transport | Transporting eroded material |
On top or sides of glacier | Supraglacial |
Where has the material usually come from? | From falling down the mountain |
Inside the ice | Englacial |
Including material that has what? | Fallen down cracks and into the ice |
Underneath the glacier | Subglacial |
What happens to the regolith? | It is dragged along the bottom of the ice |
Feature of Glacial Deposition | Drumlin |
Definition | Oval-shaped hills made of deposited boulder clay |
Boulder clay | Mixture of sand and clay |
How do glaciers deposit boulder clay | In irregular heaps |
What does the ice do? | It retreats and then advances again |
What does it do to the boulder clay? | It shapes and smooths it into rounded-shaped hills |
From where the ice advanced? | Steep side |
The direction the glacier was travelling in? | Gentle slope |
Large number of drumlins | Swarm |
Example | Clew Bay, Co. Mayo |
Feature of Glacial Meltwater | Esker |
When were they formed? | At the end of the ice age |
What happened at this point of time? | Temperatures began to rise |
What happened to the glaciers? | They began to melt |
What flowed out from the melting glaciers? | Glacial meltwater |
What did the glacial meltwater do? | It deposited material across the land surface |
What was dropped first? | Heaviest material, such as stones and gravel |
What was dropped later? | Lighter material, such as sand and silt |
Definition | A long, winding ridge of sand or gravel |
Where does the meltwater flow as the ice melts? | In tunnels beneath the ice |
What happens when it leaves an ice tunnel? | It stops immediately |
What is deposited? | Material |
Where? | At the mouth of the tunnel |
What happens to the ice? | It slowly melts back |
What is deposited? | The material |
In what form? | In the form of a long, narrow ridge of sand and gravel |
Example | Trim Esker, Co. Meath |