2.1 - Coastal processes Flashcards
What are the zones that the littoral zone can be divided into
-name them in order
coast
backshore
foreshore
nearshore
offshore
What is the backshore zone found in the littoral zone
-what is it
area between the high tide mark
- affected by wave action during major storms
What is the foreshore zone found in the littoral zone
-what is it
area between high tide and low tide mark
- seen as most important area for marine activity
What is the nearshore zone found in the littoral zone
-what is it
-area of shallow water where friction occurs between seabed and waves- causing waves to break
What is the offshore zone found in the littoral zone
-what is it
area of deeper water beyond the point where waves begin to break
friction occurs between seabed and waves- could cause distortion in wave shape
Name the 2 main types of coastlines formed by the littoral zone
Rocky/ Cliffed coastlines
- Coastal plain landscapes
What are rocky coastlines
reas of high relief
resistant rock areas- resistant to erosive power of sea, wind, rain
high energy environments
rock types: igneous, sedimentary and metamorphic rocks- granite, slate, limestone
erosion is greater than deposition
destructive waves
What is weathering
chemical, bilogical, mechanical breadown of rocks into smaller fragments in situ
What is mass movement
landslides, slumps, rockfalls all of which move material downslope under the influence of gravity
What is surface runoff
water, usually during heavy rain, flowing down cliff face and causing erosion
What is the littoral zone
-boundary between land and sea
Why does the littoral zone vary
due to:
short-term factors- daily tides, seasonal storms, individual waves
long-term factors- changes to sea levels, climate change
Name the 3 coastal landscapes the littoral zone forms
rocky, cliffed coastline
sandy coastline
estuarine coastline
What are sandy coastlines
areas of low relief with sand dunes and beaches, that are much flatter
form in areas with:
less resistant geology
a low energy environment
where deposition > erosion
constructive waves
What are estuarine coastlines
areas of low relief with salt marshes and mudflats (estuaries)
form:
in river mouths
where deposition > erosion
in a low energy environment
usually in areas of less resistant rock
What is coastal accretion
deposition of sediment at the coast and the seaward growth of coastline- creating new land
What is dynamic equilibrium
balanced state of a system when inputs and outputs balance over time
How are coastal plains maintained in a state of dynamic equilibrium in many locations
deposition of sediment from river systems inland and from offshore and longshore sources
erosion by marine action
What is a cliff profile
height and angle of a cliff face as well as its features
Name the inputs in the coastal system
inputs
marine- waves, tides
atmospheric- weather/ climate
land-rock type, structure
people- human activity, coastal management
Breakdown the coastal system
-inputs -> processes -> outputs
Name the processes in the coastal system
weathering
mass movement
erosion
transport
deposition
Name the outputs in the coastal system
erosional landforms
depositional landforms
different types of coasts
Name the 2 ways coasts can be classified
longer-term criteria:
geology
sea level change
short-term criteria:
level of energy
advancing/ retreating
How can coasts be classified by their geology
lithology (rock type) and structure of rocks
-used to determine if coast rocky, sandy or estuarine and concordant / discordant
How can coasts be classified because of sea level change
used to classify coasts as emergent/ submergent
can be caused by:
tectonic processes- lift/ subside land- effects sea levels
climate change- sea levels rise and fall
How can coasts be classified because of energy inputs
receive energy inputs form waves, tides, currents, rivers, atmospheric processes, gravity tectonics
classify coasts as high/ low energy
How can coasts be classified because of advancing/ retreating
classified as advancing/ retreating due to long-term processes (emergent/submergent) and short term (outbuilding/eroding)
What are the 2 main cliff profile types
marine erosion dominated (steep face)
- sub-aerial process dominated (curved slope profile)
What factors can determine a rocks resistance to erosion and weathering
How reactive minerals in the rock are when exposed to chemical weathering- e.g. calcite (found in limestone) can be weathered by solution, whereas quartz (found in sandstone) is not subject to chemical weathering
if rocks are clastic/ crystalline- igneous rocks are crystalline and are more resistant, sedimentary rocks are clastic (made of cemented sediment particles
if rocks have cracks, fractures and fissures, which are weaknesses exploited by the forces of weathering and erosion
What are primary coasts?
Coastlines dominated by land-based processes such as deposition
What are secondary coasts?
Coastlines dominated by marine erosion or deposition processes
What is the difference between emergent and submergent coasts?
Emergent - coasts rising relative to sea level (e.g. due to tectonic uplift)
Submergent - coasts being flooded by the sea (due to rising sea levels or subsiding land)
What is dynamic equilibrium
balanced state of a system when inputs & outputs balance over time
-this is due to balancing forces of:
-deposition of sediment from river
-erosion by marine action at coast
What are the 3 key elements to geological structure and what do they mean?
Strata - the different layers of rock within an area and how they relate to each other
Deformation - degree to which rock units have been deformed by tectonic activity
Faulting - presence of major fractures that have moved rocks from their original positions
What are concordant and discordant coastlines?
Concordant - rock strata run parallel to the coastline
Discordant - different rock strata intersect the coast at an angle
How are headlands and bays formed at discordant coastlines?
Softer rock eroded faster - creating bays
Wave refraction means lateral erosion occurs at headlands (cave arch stack stump), while wave energy in bays is much lower and erosion is reduced
How do coves form on concordant coastlines?
More resistant rock broken through by marine erosion, and the softer rock behind is then rapidly eroded to form wide coves. At the back of the coves is more resistant rock which prevents erosion further inland
What is a Dalmatian coastline?
Coastline made up of anticlines and synclines that has been drowned by rising sea levels, creating concordant coastline of long narrow islands arranged in long lines offshore
What is a Haff coastline?
A concordant coastline where long sediment ridges topped by sand dunes run parallel to the coast offshore, creating lagoons between ridges and shore
What 2 geological factors affect cliff profiles?
the resistance to erosion of the rock
the dip of rock strata in relation to the coastline
What is dip, and why is it important in determining cliff profiles?
Dip is the angle of rock strata in relation to the horizontal.
It is important as determines the stability of the cliff
What are joints?
Joints divide rock strata up into blocks with a regular shape
What are fissures?
Much smaller cracks in rocks, often only a few centimetres or millimteres long
How does folding occur and how does it create anticlines and synclines?
Folding occurs due to crustal compression - when horizontal strata are ‘squeezed’ they can be folded into a series of anticlines and synclines.
Anticlines - A shaped (convex up)
Synclines - U shaped (concave down)
What are faults?
Major fractures in rocks produced by tectonic forces and involving the displacement of rocks on either side of the fault line
What is unconsolidated sediment?
Material such as sand, gravel, clay and silt that has not been compacted and cemented to become sedimentary rock, so is loose and easily eroded
What is igneous rock (give examples) and what is it’s erosion rate?
Igneous rock is formed from the cooling and solidification of magma - e.g. granite or basalt
VERY SLOW rate of erosion (< 1mm a year) - as they are crystalline and have few joints
What is metamorphic rock (give examples) and what is it’s erosion rate?
Metamorphic rocks are rocks that have become changed by intense heat or pressure while forming. e.g. slate, marble
SLOW erosion rate (1mm to 10 cm per year) - some are crystalline, others are folded and heavily fractured
What is sedimentary rock (give examples) and what is it’s erosion rate?
Sedimentary rocks are formed from pre-existing rocks or pieces of once-living organisms. e.g. sandstone, limestone
MODERATE TO FAST erosion rate (10cm to several metres) - often clastic, and have many bedding planes and fractures
What is the difference between impermeable and permeable rocks?
Permeable - allow water to flow through them
Impermeable - do not allow groundwater flow
What is pore water pressure?
The pressure water experiences at a particular point below the water table due to the weight of water above
How does vegetation stabilise sediment?
Roots of plants bind sediment particles together making them harder to erode
When submerged, plants growing in sediment providing a protective layer (surface of sediment not exposed to moving water)
Plants reduce wind speed to reduce wind erosion because of friction with vegetation
What is the difference between halophytes and xerophytes?
Halophytes - tolerate salty conditions
Xerophytes - can tolerate very dry conditions
What is a psammosere and a halosere?
Psammosere - sand dune ecosystem
Halosere - salt marsh ecosystem
What are the stages in sand dune succession?
embryo dunes
fore dunes
yellow dunes
fixed dunes (grey)
heath/woodland
What are the roles of embryo dune pioneer plants?
stabilise mobile sand with their root systems
reduce wind speeds at the sand surface, allowing more sand to be deposited
add dead organic matter to the sand, beginning the process of soil formation
Why are sand dunes a dynamic environment?
periods of wind erosion can create low areas within dune systems called dune slacks
embryo and fore dunes are prone to wind and wave erosion, particularly during major storms, but the dune front will stabilise as long as the supply of sediment to the coast resumes
Why are estuaries ideal for the development of salt marshes?
sheltered from strong waves so sediment can be deposited
rivers transport a supply of sediment to river mouth, which may be added to by sediment flowing into an estuary at high tide
Q
What are the stages in salt marsh succession?
Algal stage - algae grows on and within bare mud, binding it together
Pioneer stage - roots begin to stabilise mud
Establishment stage - continuous carpet of vegetation established
Stabilisation - area of salt marsh rarely submerged
Climax vegetation - developed soil profile, only submerged once or twice each year
