Geomorphology Flashcards
Agents of weathering
- Water
- Ice
- Acids
- Salts
- Plants
- Animals
- Changes in temperature
Types of physical weathering
- Temperature change
- Freeze thaw/ Frost Shattering
- Abrasion - Wind, Rain, Waves
Degree of chemical weathering depends on
- Type of rock
- Temperature
How acidic rain is made:
- Fossil fuels are burnt up, releasing oxides such as nitrogen, carbon and sulphur into the atmosphere
- These oxides combine with the moisture in the air, and form nitric acid, sulphuric acid, carbonic acid
Types of Biological weathering
- Trees and other plants
- Tiny organisms
- Burrowing animals
Difference between weathering, erosion, deposition
Weathering: occurs on the spot
Erosion: weathered rocks or minerals are transported away
Deposition: comes to rest
Transporting agents
- Gravity
- Water
- Wind
- Ice
River valley sections
- Upper Course (young)
- Middle Course (aged/mature)
- Lower Course (old)
Rivers goal
To erode all land to sea level
Agents of erosion
- Rivers
- Oceans
- Winds
- Glaciers
Meander is also called
River bend
Importance of rivers to man
- For our survival: water
- For food
- Irrigation, watering our crops
- Transportation
- Energy, hydro electric power
- Leisure
Characteristics of upper course
- Closer to the source
- Steep gradient
- Small river and flows quickly
Features in upper course
- V- shaped valleys
- Interlocking spurs
- Rapids
- Waterfalls
- Gorges and canyons
Types of erosion
- Hydraulic action
- Abrasion
- Attrition
- Solution
Types of transportation
- Traction
- Saltation
- Suspension
- Solution
V - shaped valleys
Deep valleys with steep sides
Interlocking spurs
- Erosion outside the banks and vertical erosion
- Results in ridges of high land (spurs) to project towards the river, decreasing in height towards the river
Waterfalls are commonly formed
When a river crosses a band of hard or resistant rock
White water shows
A lot of turbulence
What results in rapids
Friction that is caused
River’s velocity depends on
- Gradient
- Smoother the channel/path
- Volume
Rapids
Steep slope, with rough river bed (uneven due to alternating bands of soft and hard rock)
Characteristics of Middle Course
- Gradient not as steep as Upper Course
- Lateral erosion (erosion of the banks) more effective than vertical
- More wider, open appearance
- Some deposition takes place
- Meanders are common
Features in Middle Course
- Meanders: river cliffs and slip-off slopes
- Ox-bow lakes
Meanders with river cliffs and slip-off slopes
- Outside banks are undercut creating river cliffs
- Inside banks where water flows more slowly with deposition. Giving rise to gentler slopes/slip-off slopes
Ox-bow lakes
- Sometimes meanders become so pronounced that only a narrow neck of land is left
- When a river is in flood the neck breaks
- Deposition then takes place sealing off the ends of the meander
Characteristics in the lower course
- Nearest the sea
- Gradient is gentler
- River flows slowly
- Volume of water is greater
- Transportation is mainly suspension and solution
- Deposition is more important than erosion
Features in a lower course
- Floodplain
- Levees
- Braiding
- Deltas
Floodplains
- Middle and lower course
- Alluvium is deposited on valley floor
Levees
- River floods, depositing material on flood plains
- Heavier/larger material are deposited near the river, lighter/smaller sediment is carried/deposited further away
- After successful floods, natural embankments called levees are created
Braiding
- Occurs when the river divides over various distances into two or more channels
- Occurs when the river carries a large load/the volume of the river changes rapidly from season to season
Deltas form under these conditions
- River carries large amount of sediment
- Sea is relatively calm (no waves or strong currents to carry sediment away)
- Sea is not too deep
- River flows slowly
- Vertical difference between high tide and low tide (tidal range) is not too great
Traction
In the upper course. Big rocks roll/slide down with the water
Saltation
In the upper course. Pebbles (smaller) are bounced with the movement of the water
Suspension
In the middle and lower course. Tiny grains of sand and silt/clay are held in the body of the water carried along with the flow.
Solution
In middle and lower course. Minerals that are dissolved in water are carried along in solution
Size of wave is determined by
- Speed of wind
- Length of time the wind has been blowing
- Distance of sea it has travelled over (fetch)
Hydraulic action: blow holes
Power of the waves forces air into cracks, compresses and blows the rock apart as the pressure is released
Constructive waves
- Build up beaches
- Large swash
- Lower than destructive waves
- Longer wavelength
- Made when the sea is calm
Destructive waves
- Much larger and powerful
- Made during a storm
- Travelled a long way
- Stronger backwash
- Short distance between peaks
- Much taller
Features of Coastal Erosion
- Cliffs
- Notches
- Wavecut platforms
- Headlands
- Bays
- Caves
- Arches
- Stacks
Cliffs form where…
There is harder, more resistant rock (limestone/chalk)
Wave erosion is strongest where…
The large waves break against the base of the cliff
Headlands and bays are created by
- Differential erosion and formed in alternating bands of different rock types
- Meets the coast at right angles, softer rocks erode faster to form sheltered bays
- Harder rocks are more resistant to form exposed headlands
Long shore drift: transportation of particles along a coastline is influenced by:
- Strength of waves
- Angle at which waves strike the shoreline
Spits form where:
- The coastline changes direction
- Longshore drift continues to move material along the beach
Coastal methods of Transport
Longshore drift
Coast: Features of deposition
Spits
Longshore drift will…
Deposit material in the sea after the coastline has changed direction
Spit cannot…
Develop right across the bay as a river’s estuary prevents build-up of sand
Sand spits often have a…
Curved/hooked end
Sand spits end is created by:
- Secondary wind
- Wave direction
These causes waves to strike from a different direction
Spits create…
An area of calmer water, sheltered by the spit from the waves. A lagoon can develop in this sheltered area.
Lagoon is also called
Salt marsh or dry land
Coastal landforms
- Bays
- Beaches
- Capes
- Caves
- Headlands
- Islands
- Lagoons
- Peninsulas
- Reefs
- Rocky shores
- Sea cliffs
- Tidal pools
Peninsula
- Connected by a thin land mass
- Almost an island
- Bordered by water on 3 sides
Cape
Bordered by water on 2 sides
Management of the coast
- Hard Engineering
- Soft Engineering
Hard Engineering Examples
- Sea walls = 75 years life span
- Revetments = sloped structures
- Groynes/Piers
- Rock armour/rickrap
Hard Engineering Advantages
- Immediately stops erosion
- Encourages deposition
Hard Engineering Disadvantages
- High impact on environment
- Expensive
- Less sustainable
- Short term
Soft Engineering Examples
- Beach nourishment
- Sand dune stabilisation
- Managed realignment
Soft Engineering Advantages
- Long term
- Cheaper
- Low impact on environment
- More sustainable
Soft Engineering Disadvantages
Less effective against erosion and flooding
