1.a. Coastal landscapes can be viewed as systems Flashcards
A conceptual overview of: - the components of coastal landscape systems, including inputs, processes and outputs. - the flows of energy and material through coastal systems. - sediment cells.
Define positive feedback
Where a change causes a further, or snowball, effect that continues or even worsens the original change
Define negative feedback
Acts to lessen the effect of the original change and ultimately to reverse it and return to equilibrium.
Define a sediment cell
A length of coastline and its associated near-shore area, within which the movement of coarse sediment (sand and shingle) is largely self-contained
What are the 5 physical factors affecting coastlines?
Winds, Waves, Tides, Geology, Ocean Currents.
How do winds affect coasts?
- Source of energy for coastal erosion and sediment transportation
- Winds cause waves due to friction with the ocean surface
- higher the wind speed, longer
the fetch - Sub-aerial erosion damages headlands and cliffs.
- Oblique angled winds cause same angled waves, which generate longshore drift.
What are the two types of waves?
Constructive and destructive waves.
What are the characteristics and effects of a constructive wave?
- Long wavelength, low height and low frequency.
- Usually break as spillng waves.
- Strong swash travels a long way up gentle sloping beaches.
- Swash energy exceeds backwash energy due to long wavelength.
- Deposits and carries more sediment up the beach than it takes away, building up beach.
What are the characteristics and effects of a destructive wave?
- Greater height, shorter wavelengths and higher frequency.
- Usually break as plunging waves.
- little forward tranfer of energy to move water up steep sloping beaches. - Swash slowed by friction and so does not travel far up the beach
- Short wavelength so wave backwash collides with next incoming wave, lowering swash energy and increasing backwash energy.
How are the gradients of beach profiles influenced by waves?
High energy waves, usually occuring in winter months, remove material from the top of a beach and transfer it to the offshore zone, creating a lower gradient
Low energy waves, usually occuring in summer months, build up the beach face, steepens the profile.
This is significantly affected by wave steepness, the angle of wave approach and particle size.
How do tides affect coasts?
- Tides vary between high and low daily with the rotation of the earth in relation to the position of the moon
- The size of the tidal range influences the scale at which wave action can influnce the coast.
What are spring and neap tides, and why do they occur?
- Spring tides occur when the moon and sun are aligned, and causes a max tidal range twice each lunar month.
- Neap tides occur when the moon and sun are at right angles with each other, and produces a minimum tidal range, twice each lunar month.
What are the two aspects of lithology that influence coasts?
Lithology and Structure
What is lithology and how does it affect coasts?
- Lithology refers to the physical and chemical composition of rocks.
- This can be relevant in materials such as clay being less resistant to coastal erosion, and others such as basalt being more resistant. - This can also be relevant in materials such as chalk and carboniferous limestone, where calcium carbonate is common, resulting in these materials being more vulneranle to chemical weathering.
What is the structure of geology and how does it affect coasts?
- Structure refers to the properties of individual rock types, such as jointing, bedding and faulting, and the permeability of rocks.
- For example, porous rocks can absorb and store water (PRIMARY PERMEABILITY)
- Carboniferous limestone is also permeable, but instead due to its many joints (SECONDARY PERMEABILITY) - This also affects the distribution of rock types across the coast, and the resultant shape of the coastline, e.g. concordance coastlines are straight due to a constant rock type.
How do currents affect coasts?
- Ocean currents, generated by the earth’s rotation, transfer warmer water from the middle latitudes to the poles.
- Regulated global temperatures, which can significantly affect what weathering processes occur, e.g. freeze thaw only in colder locations, or chemical weathering being sped up by higher temperatures.
