Summer Revision 2025 (river, The Sea,glaciation) Flashcards
(24 cards)
How does a waterfall form?
River flows over hard rock and soft rock .
This creates a vertical drop = waterfall.
The force of falling water and rocks creates a plunge pool at the base (hydraulic action + abrasion).
The hard rock above gets undercut and eventually collapses.
As this repeats, the waterfall retreats upstream.
E.g Powerscourt waterfall, Co. Wicklow.
What’s a source ?
Where the river begins
How does a river transport its load?
A river moves its load in four main ways:
Traction – Large stones are rolled along the river bed.
Saltation – Small pebbles are bounced along the bed.
Suspension – Tiny particles float in the water.
Solution – Minerals (like limestone) are dissolved in the water and invisible.
When does River Deposition occour?
Rivers deposit or drop their load when they begin to slow down and lose energy.
(i)
This happens:
when a river reaches flat ground when a river enters a lake or the sea
How are meanders formed?
Meanders form in the middle and lower course of a river (like the Shannon or Boyne) through erosion and deposition:
Outside bend – Water flows faster and erodes the bank (hydraulic action + abrasion).
Inside bend – Water flows slower and deposits material.
This creates a curving bend in the river called a meander.
How are levees formed?
Levees are natural raised banks found along the sides of a river, created by deposition during flooding. They are a feature of the old stage (lower course) of a river and can be seen along the River Liffey and the River Moy, Co. Mayo.
Formation:
During normal (low) flow, the river drops some of its load onto the bed, slowly raising it.
During floods, the river overflows its banks and spreads over the floodplain.
As the water spreads, it slows down and loses energy, causing it to drop its load.
Heavier materials (like sand and gravel) are dropped first, close to the riverbanks.
Finer materials (like silt and clay) are carried further out onto the floodplain.
After many floods, these repeated deposits build up raised banks, called levees.
What’s a Tributary?
A small river that joins a larger river.
What is a Confluence?
The point where a smaller river joins a larger river.
What is the Estuary?
Part of the river mouth that is tidal.
How is a delta formed?
A delta is a fan-shaped (or triangular) area of land at the mouth of a river, formed by deposition. It is a feature of the old stage (lower course) of a river.
Formation:
As the river reaches the sea or a lake, it slows down and loses energy.
This causes the river to deposit sediment (like sand, silt, and clay) at its mouth.
If waves and tides are not strong enough to carry all the sediment away, it builds up.
Over time, these deposits block the river’s main channel.
The river then splits into several smaller channels, called distributaries, to reach the sea.
These processes create a flat, low-lying delta that often looks like a fan or triangle.
Example:
The Nile Delta in Egypt
What are the five main processes of coastal erosion?
Hydraulic action: The power of water as it crashes against the coast.
A brasion: Waves pick up stones and throw them against the coast. These stones abrade the coast.
Compressed air: Air in rocks becomes trapped by the incoming waves.
The trapped air puts pressure on the rocks. When the water retreats (moves out), the air expands and the pressure drops. This repeated compression and release causes the rock to shatter.
Attrition: Stones carried by the waves hit off each other. Over time they are worn down and smoothed.
Solution: Certain rocks, such as limestone, are dissolved by the water.
How do headlands and bays form?
Bays and headlands are formed on coastlines where an area of soft rock is eroded more quickly than the hard rock in the headland. This is known as differential erosion.
Soft rock, such as sandstone, is more easily eroded and begins to form a hollow in the coast known as a bay.
The area of hard rock, such as granite, is left jutting out on either side into the sea. This is called the headland.
How is a sea cliff formed?
A sea cliff is formed by the erosion of coastal rock, mainly through the processes of hydraulic action, abrasion, and compressed air.
Formation Process:
Waves erode a notch at the base of the cliff.
As the notch enlarges, the overhanging rock becomes unstable and collapses.
The notch continues to erode, causing the cliff to retreat slowly inland.
As the cliff retreats, a wave-cut platform (a flat rocky area) forms at the base of the cliff, visible at low tide.
How are sea caves, arches, stacks, and stumps formed?
Sea Cave – Strong waves erode cracks at the base of a cliff through hydraulic action, abrasion, and compressed air, forming a sea cave over thousands of years.
Sea Arch – If the cave erodes through a headland (or two caves meet), a sea arch forms – an archway through the rock.
Sea Stack – When the roof of the arch collapses, a pillar of rock is left standing in the sea – this is a sea stack.
Sea Stump – Over time, the stack is eroded, leaving a small, low stump of rock called a sea stump.
How are sand dunes formed
Dry sand on the beach is blown inland by the wind (because it is lighter).
The sand becomes trapped by vegetation or obstacles like rocks or driftwood.
Over time, the trapped sand builds up and forms sand dunes.
Marram grass is often planted to stabilise sand dunes.
It has deep roots, is thick and coarse, and is resistant to salt.
It helps prevent sand from blowing further inland
How is a spit formed?
A spit is a narrow ridge of sand or shingle that is formed by coastal deposition, usually at a sheltered bay or river mouth.
Formation Process:
Longshore drift transports material along the coast.
When it reaches a sheltered area (like a bay), it loses energy and deposits material.
These deposits build up over time, forming a spit that extends out into the water.
As the spit grows, it may curve due to wave direction, and vegetation may begin to grow on it, helping to stabilise it.
What are the main methods of coastal protection and how do they work?
Groynes
Concrete or wooden fences built at right angles to the coast.
They trap sand moved by longshore drift, helping to build up the beach.
Example: Rosslare, Co. Wexford.
Sea Walls
Solid walls built along the shore to break the power of incoming waves.
Often curved at the top to deflect waves back out to sea.
Example: Bray, Co. Wicklow.
Gabions
Steel cages filled with stones, stacked like a wall.
They absorb wave energy and help prevent coastal erosion.
Example: Lahinch, Co. Clare.
What is plucking in glacial erosion?
Plucking is a process of glacial erosion where the glacier pulls pieces of rock from the ground as it moves.
Process:
As the glacier moves, friction between the ice and the ground creates heat.
This heat causes ice at the base to melt, forming meltwater.
The meltwater enters cracks in the rock and then refreezes, sticking the rock to the glacier.
When the glacier moves forward again, it plucks chunks of rock out of the ground and carries them away.
What is abrasion in glacial erosion?
Abrasion is a process where rocks embedded in the base of a glacier scrape and smooth the surface it moves over.
Process:
Plucked rocks become embedded in the glacier as it moves.
As the glacier advances, these rocks scrape against the ground, causing abrasion.
This scraping smooths and polishes the surface beneath the glacier, creating features like striations
What are the main features of glacial erosion?
Glaciated Valley
A V-shaped valley transformed into a U-shaped valley by the movement of a glacier, which straightens and flattens it.
Cirque (Corrie)
A large, hollow on the side of a mountain with three steep sides, formed as the birthplace of a glacier.
Tarn
A lake that forms inside a cirque.
Pyramidal Peak
A steep-sided, pyramid-shaped mountain formed by the erosion of many cirques on all sides.
Arête
A narrow, steep ridge that forms between two cirques.
Paternoster Lakes
A series of ribbon lakes (long, narrow lakes) linked together in a glaciated valley.
Truncated Spur
A cut-off part of an interlocking spur, eroded by the glacier as it moves through the valley.
Hanging Valley
A small tributary valley that is elevated above the main glaciated valley, often with a waterfall at its mouth.
How is a cirque (corrie) formed?
1.Snow accumulates in a hollow on the mountain’s side, often in a sheltered area.
2.Over time, the snow turns to ice due to pressure.
3.The ice moves and erodes the rock beneath through abrasion (scraping) and plucking (pulling out rocks).
4. This erosion carves out a bowl-shaped hollow with steep sides, forming a cirque (or corrie).
5. After the ice melts, a tarn (lake) can form at the bottom of the cirque
What are supraglacial, englacial, and subglacial materials?
Supraglacial
Materials found on the surface of the glacier (top or sides).
These materials have usually fallen from the mountain and landed on the glacier as it moves.
Englacial
Loose material trapped inside the glacier.
This includes material that has fallen into cracks in the ice and is carried within the glacier.
Subglacial
Material trapped beneath the glacier.
This loose regolith is dragged along the bottom of the glacier as it moves.
What is a terminal moraine and how is it formed?
Terminal Moraine is found at the front of a glacier.
It marks the furthest point the glacier has reached.
Formed from material that has been pushed ahead by the glacier.
Indicates the glacier’s maximum advance
What are drumlins and how are they formed?
Drumlins are oval-shaped hills made of deposited boulder clay (a mixture of sand and clay).
They are formed by the glacier moving over the land and depositing material beneath it.
Drumlins often occur in large groups, known as drumlin swarms.
