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Physical geography > Geomorphological processes > Flashcards

Geomorphological processes Flashcards

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1
Q

What is weathering?

A

The breakdown or disintegration of rock in situ by agents such as ice, salt, plant roots and acids.

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2
Q

What does weathering lead to?

A

The transportation/transfer of materials.

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3
Q

What are sub-ariel processes?

A

Processes that slowly break down the coastline, weaken the underlying rock and allow for sudden movement.

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4
Q

What is an example of negative feedback in weathering?

A

If removal of debris is slow and ineffective it leads to build up which reduces cliff exposure and prevents weathering to some extent.

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5
Q

What is an example of positive feedback in weathering?

A

If the rate of debris removal exceeds the rate of weathering and mass movement then there is an increased vulnerability of the rock and increased weathering.

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6
Q

What is mechanical weathering?

A

The break-up of rocks w/o any chemical changes taking place - physical constant movement.

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7
Q

What are the diff. types of mechanical weathering?

A
  • Freeze thaw
  • Salt crystallisation
  • Wetting and drying
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8
Q

What is freeze-thaw?

A

When water gets into cracks in the rocks and then freezes as the temp. drops. Expands as it freezes causing cracks to widen. This process repeats forcing the rock to break away and collect at base of cliff as scree.
These rock fragments can be used by the sea for marine erosion.

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9
Q

What is salt crystallisation?

A

When sea water that was in a crack in the rock evaporates leaving behind salt crystals. These can grow over time exerting pressure on the rock and causing it to break.

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10
Q

What is wetting and drying?

A

Occurs because rocks rich in clay such as shale expand when they are wet and contract as they dry causing rocks to crack and break.

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11
Q

What is biological weathering?

A

The breakdown of rocks due to organic activity.

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12
Q

How do plants cause weathering?

A

Plant roots grow into small cracks in rock beneath the surface or in cliff face. Cracks widen as roots grow. Cause rock to break up.

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13
Q

How does bio weathering contribute to chemical weathering?

A

Water running thro decaying veg becomes acidic - increased chem. weathering.

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14
Q

How do animals contribute to bio weathering?

A

Birds like puffins and sand martins and mammals like rabbits can burrow into cliffs causing rocks to crack.
Marine organisms like piddocks can also burrow into the rock.

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15
Q

What is chemical weathering?

A

Involves a chemical reaction where salts may be dissolved or clay like deposit may be a result which is easilt eroded.

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16
Q

What are the diff. types of chem. weathering?

A
  • Carbonation
  • Oxidation
  • Solution
17
Q

What is carbonation?

A

When rainwater absorbs carbon dioxide from the air to form a weak carbonic acid. This reacts w/ calcium carbonate in rocks (limestone, chalk) and forms calcium bicarbonate which is easily dissolved. Cooler rainwater, more CO2 absorbed.

18
Q

What is oxidation?

A

Reaction of rock minerals w/ oxygen to form a rusty powder. Leaves rocks more vulnerable to weathering.

19
Q

What is solution?

A

The dissolving of rock minerals e.g. halite (rock salt)

20
Q

What are marine processes?

A

Processes that operate along the coastline and are connected w/ the sea e.g. tides, waves, LSD

21
Q

What is hydraulic action?

A

The sheer force of water as it crashes against the coastline. Air becomes trapped and compressed in cracks in the rock.
Leads to cavitation.

22
Q

What is cavitation?

A

When water retreats compressed air expands weakening the cracks.
Bubbles formed in the water may implode under high pressure generating tiny jets of water which erode over time.

23
Q

What is wave quarrying?

A

The action of waves breaking against unconsolidated material like sands and gravel. Waves scoop out loose material and carry it away as sediment.

24
Q

What is corrasion?

A

When waves pick up sand and pebbles from the seabed and it is thrown at cliff face by waves. Slowly chips away at rock and smooths the surface.

25
Q

What is abrasion?

A

Similar to corrasion but has more ‘sandpapering’ effect. Sediment dragged up and down coastline eroding and smoothing rocky surfaces. Can result in formation of wave-cut platform.

26
Q

What is solution?

A

Weak acids in seawater can dissolves alkaline rock or the alkaline cement that bonds rock particles together.

27
Q

What is attrition?

A

When bits of rock in the water smash against each other and break into smaller rocks. Results in smooth and round stones in the water.

28
Q

In terms of transportation, what is solution?

A

Substances that can or are dissolved being carried along in the water.
E.g. limestone carried in water that is slightly acidic.

29
Q

What is suspension in terms of transportation?

A

Fine material such as clay or silt whipped up by turbulence and carried along in the water. This is how most eroded material is carried.

30
Q

What is saltation?

A

Larger particles like pebbles or gravel that are too heavy to be carried in suspension. They bounce along the seabed.

31
Q

What is traction?

A

When very large particles like boulders are pushed along the seabed by the force of the water.

32
Q

How does longshore drift transport sediment?

A

When swash carries sediment up the beach parallel to the prevailing wind and backwash carries sediment back down the beach at a right angle to the shore. Sediment is moved along the coast.

33
Q

What are the main factors affecting coastal erosion?

A
  • Waves
  • Rock type
  • Sub-ariel processes
  • Geological structures
  • Management
  • Absence or presence of beach
34
Q

What is marine deposition?

A

Sediment carried by seawater is deposited.

35
Q

What is aeolian deposition?

A

Sediment carried by wind deposited.

36
Q

When do marine and aeolian depos. occur?

A

When sediment load exceeds ability of water or wind to carry it. This can be because sediment load increases (landslide etc.) or wind or water flows slow down (has less energy).

37
Q

Why do wind and water flows slow down?

A

Friction increases - Waves enter shallow water or wind reaches land, friction between wind/water and ground = slow

Flow becomes turbulent - water or wind encounters obstacle (current in opposite direction, veg. etc.) flow becomes rougher and slower.

38
Q

How does the wind dropping affect waves?

A

Wave height, speed and energy decreases.

Physical geography (17 decks)

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