Coastal Landscapes 1.2 Flashcards
List the 5 geomorphic processes
weathering - mass movement - wave processes - Fluvial processes - Aeolian processes
Describe the three different types of weathering
Physical or mechanical - breakdown of rock is largely due to this - breaks it down into smaller pieces - freeze-thaw - thermal expansion - pressure release - salt crystallisation
Chemical - to do with the decay of rock - produces weak material that may be easily removed by erosion or transportation - mostly occurs in higher temperature tropical climates
Biological - growth of plant roots or chelation by organic acids - biological processes usually classed as a separate type of weathering
What is mass movement
occurs when the force acting on the slope material exceeds the force trying to keep the material on the slope
contributes to the sediment budget by transporting rock and regolith to the beach bellow
main processes are rock fall on more than a 40 degree slope or slides along a straight line slip plane
Describe the different processes of coastal erosion
Erosion - breaking waves erode the coastline through many processes
abrasion when rocks are thrown from the sea against the cliff
hydraulic action when air gets into cracks and expands
attrition when rocks collide and break up
pounding when the mass of a breaking wave exerts pressure on the rock
Solution when rocks dissolve
Describe the different processes of coastal transportation
Transportation - when waves and tides carry material away from the shore
Solution - minerals are dissolved in the water - will remain invisible until the after is evaporated
Suspension - small particles of silt, sand or clay are carried by current - accounts for the appearance of some sea water
Saltation - where material is picked up for a short time but is too heavy to be continuously carried so is put down again
Traction - the largest particles may be pushed along the sea floor by the force of the flow
Describe how coastal deposition occurs
material is deposited where there is a lack of energy - often occurs where there is more accumulation than removal - waves immediately slow down after breaking - low energy environments - the velocity at which they’re deposited is known as the settling velocity
what is the rate they are deposited known as?
The settling velocity
What are Fluvial processes?
Erosion - Transportation - Deposition - important in river mouths and play a part in the development of landforms.
What do each of the fluvial processes do?
Erosion - In the upper catchment it provides the main source of the rivers load - similar processes to the sea which occur in high energy areas.
Transportation - Traction, solution, saltation,suspension
Deposition - As rivers enter the sea there is a notable lack in velocity - tides and currents moving in the opposite direction slow the flow - largest particles deposited first - small ones out at sea as it is sequential.
What are Aeolian processes
Erosion - Transportation - Deposition - Due to exposure coastal landscapes can be shaped by the wind.
What do each of the Aeolian processes do?
Erosion - Wind is able to pick up particles of sand and move them by deflation - moved by surface creep and saltation - restricts abrasion to 1m height as sand is heavy - dry sand is better and carried further - carried much further in wind than water
Transportation - bar solution uses the same processes as water - only tiny grains are carried by suspension
Deposition - deposited once the wind speed falls - occurs usually inland where vegetation causes surface friction.
How are cliffs and shore platforms formed?
When destructive waves break repeatably on steep sloping coastlines - undercutting can occur between high/low tide - continued undercutting causes weakness in the strata above - this then collapses causing a steep cliff profile - causes the cliff to retreat inland parallel to the coast
as the sequences continues the cliff retreats and the platform at its base - as the platform increases in size wave break on it rather than the cliff - slopes towards the sea around 3 degrees - freeze thaw and salt crystallisation
How are bays and headlands formed?
Typically formed adjacent to each-other due to bands of rocks differing in resistance - if they lay perpendicular to the coastline - less resistant are eroded quicker to form bays - Causes a discordant coastline to form - rocks lying parallel to the coastline create a concordant coastline.
Irregularly shaped coastlines cause wave refraction - waves bend around the headland as they slow in shallower water and speed up in deeper - Orthogonal’s converge around headlands and disperse in bays
How are geos and blowholes formed?
Geos - narrow step sided inlets which are formed where fault lines have been more rapidly eroded by wave action i.e. hydraulic action
Blowholes - Formed when geos form like a long cave at a right angle to the cliff and suffers a vertical roof collapse
How does the formation of caves - arches - stacks and stumps occur
Individual or a sequence of erosional landforms which develop around headlands - wave refraction causes energy to focus on the sides of headlands - points of weakness are exploited by wave action - causes a small cave to form - wave attack between high and low tides may cause it to break through and form an arch - continued erosion weakens its support - aided by weathering it may collapse - leaves an isolated stack - this may be destroyed by waves in a storm leaving a smaller stump.
