Coasts Revision Flashcards
What is the littoral zone and what are the changes?
The area of the coast that can be affected by wave action.
It is a dynamic zone which means its constantly changing due to the interaction between processes on land and in the sea.
These changes can be:
- Long - term due to climate or sea level changes
- Short term due to the tides, waves, and storms
What are the four parts of the littoral zone?
- Backshore is usually beyond the influence of wave action but can be affected during storm events
- Foreshore is the intertidal area between high and low tide
- Nearshore is the breaker zone where friction between the seabed and the waves causes them to break
- Offshore is the area outside the influence of waves
What are concordant coasts?
A concordant coastline is a coastline where the same type of rock runs parallel to the coast, and the layers of rock are folded into ridges. Concordant coastlines are also known as longitudinal or Pacific type coastlines
Example: Durlston Bay
What are discordant coasts
A discordant coastline is a coastline where bands of different rock types run perpendicular to the coast, resulting in the formation of headlands and bays
Example: Lulworth cove
Eustatic sea level change
Eustatic sea level change is a global change in the amount of water in the oceans or the shape of the ocean basins.
Caused by changes in ocean water volume and temperature
Impact seen in tropical oceans
What is Isostatic sea level change?
Isostatic sea level change is a local/regional change in sea level that occurs when the land rises or subsides relative to the water
The Earth’s crust floats on a denser underlying layer (asthenosphere), which is in balance when the weight of the crust is exactly balanced by its buoyancy
The addition of a load at a particular point of the crust (water, ice or increasing sediment at a delta) upsets the equilibrium and some of the asthenosphere floats away, causing isostatic depression as the land level falls
What are Emergent Coasts?
Emergent coastlines are coastlines that have been created when the sea level has fallen relative to the land. This can happen when the land is uplifted or when the sea level falls
What are Submergent Coasts?
Coastlines that have been submerged underwater due to a rise in sea level.
They are the result of areas of land that were once part of the terrestrial land being inundated by the sea
What are the characteristics of a high energy coast?
- Destructive waves
- Exposed to strong winds and long fetches
- Higher rates of erosion and deposition
- Tend to be rocky coasts
- Steep cliffs - marine cliff profile
- Less steep cliffs - subaerial cliff profile
Headlands, wave - cut platforms
What are the characteristics of a low energy coast?
- Constructive waves
- Sheltered locations with short fetch
- Higher rates of deposition than erosion
- Sandy beaches, salt marshes, estuarine and tidal mud flats
- Gentle relief
- Sediment from land and sea
Beaches, spits, coastal plains
Why do coastal plains occur?
They usually occur where the land gradually slopes down towards the sea, tend to be low relief
Coastal plains include both:
- Sandy coastlines
- Estuarine coastlines
What are primary coasts?
dominated by land-based processes, such as deposition from rivers
What are secondary coasts?
dominated by marine erosion or deposition processes
Wave tide types?
Microtidal coasts – have a tidal range of 0-2m
Mesotidal coasts – have a tidal range of 2-4m
Macrotidal coasts – tidal range greater than 4m
Dalmatian coastlines?
Named after the Dalmatian region of Croatia.
Feature long islands and coastal inlets that run parallel to the coastline.
Normally occur in high energy environments from where there is eustatic or isostatic change creating a submerging coastline.
Haff coastlines?
Named after the Haffs, or lagoons, of the southern shore of the Baltic Sea.
Characterized by long spits of sand that run parallel to the low coast.
What is differential erosion?
The difference in rates of erosion due to some rock types being more resistant than others. More resistant rocks erode more slowly than less resistant rocks
What are the 4 processes of erosion?
Hydraulic action - the most powerful (affects rocks of all resistance)
Abrasion - needs looser sediment to be effective, or soft sedimentary rocks
Attrition - only acts on already eroded sediment - soft sedimentaries are easily rounded
Solution - mainly affects limestone, which is vulnerable to solution by weak acids
What is flocculation?
when very small clay particles clump together in the water (in suspension) and eventually become large enough to sink.
What are the different weathering types?
Mechanical weathering processes include freeze - thaw and salt crystallisation
Chemical weathering includes solution (carbonation)
Biological weathering includes plant roots and animal activity
What are the different types of mass movement?
Landslide: A rapid downslope movement of large blocks of rock and soil along a line of weakness in the rock, such as a fault. Landslides are common on steep slopes and in areas where rocks are being undercut.
Mudflow: A slow or rapid flow of saturated soil down a slope. Mudflows can be destructive when they reach plains or piedmonts, and are common near erupting volcanoes.
Slump: A type of slide where a mass of earthen material moves downslope in one piece. Slumps often occur when clay-rich soil becomes saturated and slippery.
Rockfall: Bits of rock fall off a cliff face, usually due to freeze-thaw weathering.
Rotational slip: Saturated soil slumps down a curved surface.
What is isostatic rebound?
Isostatic rebound occurs for example, when an ice sheet melts and the land slowly starts to rise again (happening in SE England now) this is known as glacio-isostasy
What is glacio-eustatic changes?
It’s when ice sheets melt
What are emergent landforms?
raised beaches (formed when sea levels were much higher than now)
What are submergent landforms?
rias (river valleys drowned after sea ice melts), River Fowey estuary, Cornwall and fjords (drowned glacial valleys), Norway
Who will sea level rise affect?
Sea level rise may affect a different number of people due to:
Different populations in low lying coastlines
Can be ideal for agricultural fertility
Why do sea levels rise?
Melting glaciers and ice sheets: As glaciers and ice sheets melt, they add water to the ocean.
Thermal expansion: As the ocean warms, its water expands.
Changes in land-water storage: Changes in the amount of water stored in lakes, rivers, aquifers, and reservoirs, as well as changes in precipitation patterns, can contribute to sea level rise.
Vertical land motion: The Earth’s crust rebounds and subsides, which can affect sea levels.
Human activities: Human activities, such as burning fossil fuels, are the main driver of climate change.
What are erosional processes?
Erosional processes refer to how natural forces like water, wind, ice, and biological activity wear away the Earth’s surface.
What are mass movement processes?
Mass movement refers to the downslope movement of rock, soil, and debris due to gravity.
How many types of erosional processes are there?
6
What are the types of erosional processes?
Hydraulic Action: The force of moving water that breaks down rocks.
Abrasion: Rocks or sediment scrape against surfaces, wearing them down.
Attrition: Rocks and pebbles collide and break into smaller, smoother pieces.
Corrosion: Chemical dissolution of rocks, especially limestone, by acidic water.
Solution: Rocks dissolve directly in water, particularly limestone in coastal and river environments.
Wind Erosion: Wind removes fine particles (deflation) or wears down rock surfaces (abrasion).
These processes shape various landforms, such as cliffs, valleys, waterfalls, caves, and glacial features.
How many types of mass movement processes are there?
6
What are the types of mass movement processes?
Soil Creep: Slow, gradual movement of soil down a slope due to freezing/thawing or plant growth.
Mudflow: Rapid flow of water-saturated soil and debris, often after heavy rain.
Landslides: Sudden, rapid movement of large masses of rock and debris, triggered by rain, earthquakes, or human activity.
Rockfall: The rapid fall of rocks from steep slopes, often due to freeze-thaw weathering.
Slump: A downward, rotational movement of a section of slope, often caused by erosion or water.
Debris Flow: A fast-moving flow of rocks, soil, and water, more destructive than mudflows.
Factors influencing mass movement include water, slope angle, vegetation, and human activity. These processes create landforms such as scarps, talus slopes, and debris cones.
What landforms are form at emergent coasts?
Forms:
1. Raised beach = is a flat, sandy or pebble-covered beach that sits above the current sea level
2. Fossil cliffs = is a steep slope at the back of a raised beach that was formed by marine erosion but is now above high tide
What are types of depositional landforms?
- Spit = A beach spit is a long, narrow ridge of sand or shingle that extends from the land into the sea (Example = Holderness coast)
Caused by:
Longshore drift: Longshore drift carries sediment along the coastline in a zig-zag pattern.
Deposition: When the coastline changes direction, the energy of the longshore drift disperses, causing deposition on the sea bed.
- Sand Dune = A dune is a natural hill or ridge made of sand that forms when wind blows sand into a sheltered area
Formation:
Sand dunes are formed when wind blows sand off the beach and deposits it around an obstacle, like a rock or driftwood. The sand builds up into ridges, called embryo dunes, that grow in size over time
Stabilization
Vegetation, such as marram grass, stabilizes the dunes through a process called plant succession.
Conditions
Sand dunes form where the rate of beach deposition is greater than erosion. The stronger the wind, the higher the dunes will be.
- Bayhead beach (Lulworth cove)
Swash - aligned feature = where waves break parallel to the shoreline and move sediment into a bay, where a beach forms. Erosion is concentrated at headlands and the bay is an area of deposition
Why does deposition occur?
Deposition occurs when waves no longer have sufficient energy to continue to transport material
This loss of energy might be due to:
- the wind dropping, removing an energy source
- resistance by obstruction, e.g. a groyne or headland
- dissipation of energy through refraction
- friction from extended transport across shallow angled nearshore and foreshore zone
Sediment is deposited when the force transporting the sediment drops.
- Deposition occurs in two main ways:
Gravity settling occurs when the energy of transporting water becomes too low to move sediment. Large sediment will be deposited first, followed by smaller sediment (pebbles -> sand -> silt)
What is flocculation?
Flocculation
This process is important for very small particles, like clay, which clump together and become large enough to sink
- Flocculuation is a depositional process that is important for very small particles, such as clay, which are so small that they will remain suspended in water. Clay particles clump together through electrical or chemical attration, and become large enough to sink.
What landforms are created by weathering?
Forms:
1. Talus scree (St Oswald’s slope)= A mass of small loose stones that form or cover a slope on a mountain due to:
Mechanical weathering, in particular:
Freeze-thaw weathering
A type of erosion that occurs when water enters cracks in rocks and freezes, causing the crack to widen. This process continues until the rock breaks causing blackballs
- Rotational scar slope = The scar left behind due to rotational slump
Chemical weathering when heavy rain reacts with permeable minerals in rocks and saturates them leading to material coming away from the cliff face - A terraced cliff profile = a stepped cliff face that’s created by eroded rocks and fractures or lithology in the rock.
