EQ1 Flashcards
Igneous rock?
Erode/weather very slowly due to their strong resistance (they have interlocking crystals) Few joints and weaknesses
2 examples of igneous rock?
Granite and Basalt
Metamorphic rock?
Changed from heat and pressure - mostly very hard
2 examples of metamorphic rock?
Marble, Slate
Sedimentary rock?
Formed from soil, very weak, moderate erosion rates
How does undercutting form?
Resistant strata erodes and weathers slowly, therefore will retreat less rapidly, leading to overhang above and collapse (undercutting)
Why do permeable rocks tend to be less resistant to weather?
because water percolating (the movement of water through the soil itself) comes into contact with a large surface area that cannot be chemically weathered
Emergence and submergence meaning?
emergence = getting bigger/growing
submergence = getting smaller/sinking
Case study about emergence and submergence?
10,000 years ago - ice age
As the ice flowed down, it covered half the UK
crustal loading? Ice pushed Scotland down, by dynamic equilibrium means south england rose (emergent).
Now isostatic rebound is happening where scotland is now emerging and south england is submerging
Features of a rocky/cliffed coastline?
destructive waves, has high relief, resistant rock, erosion is greater than deposition, high energy environments
Features of a sandy coastline?
Low relief areas generally flat, soft rock and low energy environments, deposition is greater than erosion, constructive waves
Features of an Eustuarine coastline?
Low relief areas with salt marshes and mudflats which are vegetated, river mouths, deposition greater than erosion, soft rock and low energy environment
3 short term coast classification criteria?
Energy inputs : tides, currents, rivers, precipitation cresting high and low energy coastlines (12.5 hour period)
Sediment inputs: Depostion and erosion rates, if the deposition is higher, it means the coastline is expanding and if erosion rates are higher, it means the coastline is
eroding
Advancing and retreating: Erosion and deposition affect whether a coastline is advancing or retreating, and also whether the coastline is emergent or submergent (sea level rising)
2 long term coast classification criteria?
Geology: The lithology (rock type) and structure (arrangement of rocks). Used to determine whether a coast is rocky, sandy or estuarine - and also concordant (parallel) or discordant (perpendicular)
Sea level change: Used to classify emergent and submergent coasts. Climate change (sea level rise) can cause a coast to become submergent. Also tectonic plate movement can lift or submerge sections of land
ROCKY COASTS VS COASTAL PLAINS:
ROCKY COASTS?
-1000km of mainly north and west coastlines
- Vary in height from high (Scotland) to low relief (Cornwall)
- Geology is resistant and they erode slowly
ROCKY COASTS VS COASTAL PLAINS:
Sandy plains?
- low relief often containing wetlands and salt marshes
- Low energy environment with high deposition
- Most of UK’s south and east coastlines (Swanage)
Concordant coastline?
When rock strata runs parallel to the coastline. One continuous layer of hard rock protecting the other layers behind it - SOUTH COAST
Discordant coastline?
Different layers of resistant and soft rock in bands which will form bays - EAST COAST (perpendicular to the coastline)
Faults?
major fractures created by tectonic plates, causing a fault line which increases the rate of erosion
joints?
and how do they form in igneous and sedimentary rock?
fractures created without the rock being moved, occur in most rocks.
In igneous rock they can form during magma cooling. in sedimentary rock they form through compression and stretching from overlying rock.
Fissures?
These are more open than fractures and can be found as a characteristic of most rocks on the earth surface.
Folding?
Bends in the rock. Produced by sedimentary rock layering - main types anticlines (folding is upward) and synclines (folding downward)
Permeable rocks?
allow water through them because they contain pores (e.g. chalk)
examples are sandstones and limestones
Longshore drift?
Swash is dependant on the prevailing wind
Largest deposition objects are rolled = traction
Smaller ones skip = saltation
Smallest is in the flow of the water = suspension
Floccuation?
A deposition process for small particles e.g. clay which are so small that they remain suspended in water. These particles clump together due to electrical or chemical attraction and become large enough to sink/deposit
4 geological factors affecting the shape of the coastline?
Horizontal dip
seaward dip, high angle
seaward dip, low angle
landward dip
Horizontal dip?
Vertical or near vertical profile with notches reflecting strata that are more easily eroded
Seaward dip, high angle?
sloping low angle profile with one rock layer facing the sea; vulnerable to rock slides down the dip slope
Seaward dip low angle?
Profile may exceed 90° producing areas of overhanging rock; very vulnerable to rock falls
Landward dip?
Steep profiles of 70-80° producing areas very stable cliff with reduced rock fall
Coastal morphology?
Relates to the rock type and geological structure
Lithology?
rock type
Hydrolic action?
where a wave breaking against a rock traps air into cracks under pressure, which is then released suddenly as the wave retreats.
Abrasion?
when material carried by waves is used as ammunition to wear away the rocks on a cliff as it is thrown against it by each wave
Attrition?
Loose rocks are broken down into smaller and more rounded pebbles which are then used in abrasion
Solution?
when sea water dissolves certain types of rocks e.g. limestone, chalk
Coastal accretion?
The deposition of sediment at the coast and the seaweed growth of the coastline, creating new land
Why are permeable rocks easily eroded?
They allow water to pass through them. Groundwater can weaken rocks by removing the cement that bind the rock sediment resulting in slumping
How can loosely-arranged sediment on the coastline be protected?
By the action of plants acting as stabilisers e.g. salt marshes, mangroves and sand dunes
What are halophytes?
Plants that can tolerate salt water
What are xerophytes?
plants they can tolerate very dry conditions e.g. those found at coastal sand dunes
How are sand dunes effective in encouraging coastal accretion?
Through plant succession:
The succession starts with halophytic plants that are capable of growing in salty sand
Once established, they trap more sand leading to formation of embryo dunes
The dunes gradually become fixed and the plant cover develops into a climax community of health/woodland
How does plant succession occur on bare mud deposited in estuaries?
The succession starts with algae, followed by various halophytic grasses etc leading to a climax community of rush and sedge
What 3 marine processes do waves influence?
erosion
transportation
deposition
3 factors that influence a wave size and strength?
Strength of the wind
Beach morphology
water depth and fetch
3 features of a constructive wave?
Low in height and long in length
Strong swash and weak backwash
Deposits sediment on the beach
3 features of a destructive wave?
High and short in wavelength
Weak swash and strong backwash
Erodes the beach
What is beach morphology?
The shape of a beach, including its width, slope (beach profile), features and type of sediment
4 beach features of prevailing wave conditions?
Storm beach - caused by constructive waves in stormy weather
Berms - Small ridges created by constructive waves during calm weather
Cusps - Product of gentle destructive waves eroding berms
Offshore bars - Former by persistent destructive waves
3 times when erosion happens?
Waves approach the coast at right angles
Heavy rainfall weakening the rocks
Debris at the foot of the cliff has been removed and no longer protects this point
3 types of weathering?
Mechanical
Chemical
Biological
2 examples of mechanical weathering?
Freeze-thaw - repeated force applied to cracks in the rock from water as it freezes
Salt crystallisation - When salt crystals grow and exert pressure within cracks and rocks
2 examples of chemical weathering?
Carbonation - The dissolution of limestone from the weak carbonic acid in rainwater
Oxidation - The reaction of oxygen to minerals, which produce iron oxide
2 examples of biological weathering?
Plant roots - the action of tree and plant roots forcing rocks apart as they grow into the cracks
Rock boring (making a hole) - When species such as clams bore holes into the rock
Mass movement?
A term for the processes responsible for the downslope movement of weathered material under gravity causing large scale cliff collapse
2 things that can cause a change in sea level?
What do both of these result in?
A change in land level (isostatic change)
Volume of the sea (eustatic change) - thermal expansion
Both result in large areas of land being submerged beneath the sea
What is the current rate of rise of the sea?
2mm per year
2 components of global sea level rise?
Thermal expansion
Melting of the ice sheet
3 physical factors that cause rapid coastal recession?
Soft/unconsolidated cliff/rocks
Large destructive waves
Strong longshore drift
2 human actions that cause rapid coastal recession?
River Dams reducing the supply of sediment to the coast (Aswan Dam Case Study)
Dredging the seabed for sand and gravel
3 high risk areas of flooding?
Estuaries
Deltas
Coastal plains
2 ways that the risk of flooding is being increased?
Rising sea level
human actions - removal of coastal vegetation which protect the coast e.g. mangroves
What will happen to storm surges, cyclones and depressions due to climate change?
They will intensify their frequency and magnitude
traction?
heavier sediments e.g. boulders, roll along the sea floor
The succession starts with algae, followed by various halophytic grasses etc leading to a climax community of rush and sedge
saltation?
sediment bounces along the floor
suspension?
fine sediment is carried within the body of the water
solution?
dissolved sediment is carried in the water as a solution (calcium carbonate)
3 types of mass movement?
Landslide - when there is sudden movement of weathered rock
Rotational slides - when large masses of unstable rocks/materials overly impermeable rocks move downslope
Rockfalls - when blocks of rock are dislodged by weathering and erosion
bar?
a beach extending across the coast with a lagoon behind it
tombolo?
a sand/shingle bar that attaches a former offshore island to the coast
spit?
a beach ridge extending beyond a turn in the coastline
cuspate foreland
a triangular area of beach extending out from a shoreline, possible formed by LD from opposing direction
