Geography 4.3 Flashcards
What types of rocks are found at concordant coastlines?
Soft rocks such as sand or clay, erode more quickly
Hard rocks like chalk and sandstone are stronger and dont erode as easy
What features are found in a CONCORDANT coastline?
Where different layers of hard and soft rocks make up the coastline stacked on top of each other along its length
What features are found on a DISCORDANT coast?
A discordant coastline occurs where bands of different rock type run perpendicular to the coast. The differing resistance to erosion leads to the formation of headlands and bays.
Examples of discordant and concordant
Dorset has both both discordant and concordant coastlines. The discordant coastline is studland bay, ballard point, swanage bay and durlston head. After Durlston Head, the strata stop alternating and the coastline is made up of hard rock. This concordant coast has fewer features.
Difference between Joints and faults and how they effect erosion?
Joints and faults are types of fractures. A joint is a fracture along which no movement has taken place, usually caused by tensional forces. A fault is a fracture or break in the rock along which movement has taken place. One might expect more earthquakes to occur near faults.
Difference between hard and soft rock?
Soft rock is easier to erode than hard.
Soft rock like chalk and clay
Hard rock like granite and chalk
Headlands and bays
Headlands are formed when the sea attacks a section of coast with alternating bands of hard and soft rock.
The bands of soft rock, such as sand and clay, erode more quickly than those of more resistant rock, such as chalk. This leaves a section of land jutting out into the sea called a headland.
The areas where the soft rock has eroded away, next to the headland, are called bays.
Wave cut platforms?
Where concordant coastlines get eroded by the sea. The sea attacks the base of the cliff forming a wave-cut notch.
The notch increases in size causing the cliff to collapse because of the layers of soft rock.
The backwash carries the rubble towards the sea forming a wave-cut platform.
Arch/stack/stump characteristics and how their formed:
Caves occur when waves force their way into cracks in the cliff face. The water contains sand and other materials that grind away at the rock until the cracks become a cave. Hydraulic action is the predominant process.
If the cave is formed in a headland, it may eventually break through to the other side forming an arch.
The arch will gradually become bigger until it can no longer support the top of the arch. When the arch collapses, it leaves the headland on one side and a stack (a tall column of rock) on the other.
The stack will be attacked at the base in the same way that a wave-cut notch is formed. This weakens the structure and it will eventually collapse to form a stump.
Factors that effect wave energy:
The size and energy of a wave is influenced by:
how long the wind has been blowing
the strength of the wind
how far the wave has travelled (the fetch)
Where in the uk has the biggest waves and why?
In Cornwall the prevailing wind is inward, has narrow shelfs and steep slopes
Destructive waves
Destructive waves are created in storm conditions.
They are created from big, strong waves when the wind is powerful and has been blowing for a long time.
They occur when wave energy is high and the wave has travelled over a long fetch.
They tend to erode the coast.
They have a stronger backwash than swash.
They have a short wave length and are high and steep.
Mass movement
Different mass movements occur on slopes under different conditions. We’ll look at four types; rockfall, mudflow, landslip and soil creep.
Rockfall is the rapid, free-fall of rock from a steep cliff face
Mudflow occurs on steep slopes over 10°. It’s a rapid sudden movement which occurs after periods of heavy rain.
Landslips or landslumps are occasional, rapid movements of a mass of earth or rock sliding along a concave plane.
Soil creep is a very slow movement, occuring on very gentle slopes because of the way soil particles repeatedly expand and contract in wet and dry periods.
How dose rock fall breaks down cliffs?
Rockfall is the rapid, free-fall of rock from a steep cliff face. Rock fragments fall from the face of the cliff because of the action of gravity. This is made worse by freeze-thaw action loosening the rock. Bare, well-jointed rock is very vulnerable to rockfall - water enters the joint, freezes and expands, cracking the rock. A scree slope of fallen rock is formed at the bottom of the cliff.
Weathering (biological, chemical and freeze thaw weathering.
Freeze thaw
Water expands slightly when it freezes into ice. The formation of ice can also break rocks. If water gets into a crack in a rock and then freezes, it expands and pushes the crack further apart. When the ice melts later, water can get further into the crack. When the rock freezes again, it expands and makes the crack even bigger.
Biological
Animals and plants can wear away rocks. This is called biological weathering. For example, burrowing animals such as rabbits can burrow into a crack in a rock, making it bigger and splitting the rock.
Chemical
The weathering of rocks by chemicals is called chemical weathering. Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it. Minerals in rocks may react with the rainwater, causing the rock to be weathered.
