Enquiry Question 1 Flashcards
Backshore
The cliff or sand dunes, plus the upper beach closest to the land.
Foreshore
The lower part of the beach which is covered twice a day at high tide; receives the most regular wave action
Nearshore
The section of the littoral zone between the low tide level and the deeper offshore water
Offshore
The section of the littoral zone that consists of deeper water in which waves maintain their shape and speed, furthest from the land.
Littoral Zone
The coastal zone - the boundary between land and sea
Berm
The shingle ridges often found towards the back of a beach
Breakers
As waves come closer to shore they break, forming a foamy, bubbly surface
Surf Zone
Zone of breaking waves
Bar
Elongated sand body created by tidal currents or waves
Lithology
The type of rock
What are the different types of coastlines?
- Cliffed coasts
- Sandy coastlines
- Estuarine coastlines
Concordant coastline
Coastline where one rock type runs parralel to a stretch of coastline
Discordant coastline
Coastline where alternating strata of differing rock types run perpendicular to the coast
Submergent coastlines are formed when:
When sea levels rise (e.g due to climate change or post glacial melt), low lying coastal plains are submerged
Rocky coasts are a result of:
They are a result from resist geology (withstand erosive forces of sea, rain and wind)
Where are rocky coasts found?
In high energy environments
Where are Coastal plain landscapes found?
They are found near areas of low relief and often in a low energy environment
Coastal plain landscapes are a result from:
Result from supply of sediment from different terrestrial and offshore sources.
Retreating coast
Erosion > deposition
Coastline accretion
Deposition > erosion causing the coast to advance
Dynamic equillibrium
Coastal processes vary but landform formation is continous and stays the same
Morphology
Features and landscapes. The result of coastal processes.
Haff coastlines are:
Where bars of sediment run parallel to the coastline, creating lagoons.
Formation of Haff coastlines:
CC
- During the last glacial period (Devensian), the sea level was about 100m lower than today as water was retained in huge ice sheets.
- Meltwater rivers on land beyond the ice front deposited thick layers of sand and gravel, creating outwash plains. The deposition produced geological structure parallel to the coastline.
- In the Holocene, 12,000 yrs ago, Interglacial constructive waves pushed the ride of sands and gravel landwards as sea levels rose.
- Sand ridges formed bars across some bays and river mouths with trapped river water- forming a lagoon behind, called Haffs.
3 examples of a Concordant coastline:
- Haff Coasts
- Dalmation Coast
- Lulworth Cove
Formation of Dalmation Coast
CC
- Two tectonic plates push towards each other, compressing the crust to create folds.
- The folds have anticlines and synclines
- Post glacial sea level rise has submerged the synclines leaving the anticlines sticking up parallel to the coast.
Formation of Lulworth Cove
CC
- It is on a landscape of alternating bands of geology that lay parallel to the coastline, horizontally organised.
- Weaknesses in the layered rock (clay) are exposed to marine processes so are targeted and broke down by erosional processes.
- The cove is formed out of the landscape after it gets behind the clay.
- It is unable to erode further due to the different type of rock behind it (chalk)
Formation of Swanage Bay
DC
- There are alternating bands of rock types (hard and soft) perpendicular to the coast.
- This is significant due to there being different levels of erosion
- The headland absorbs all the wave energy due to wave refraction
- As the wave gets more shallow, the wave experiences friction with the sea bed and breaks.
- Wave refraction occurs once headlands and bays exist because the headlands cause the wave to break due to the shallower water around them.
- Handlands absorb wave energy
- Rates of erosion are drawn towards the headlands; deposition occurs inside the bay - making a beach
2 examples of a Discordant coastline
- Swanage Bay
- West Cork, Ireland
West Cork, Ireland coastline description
- South west of the UK
- Waves are more powerful
- It faces Bantry Bay, where it experiences high wave energy due to waves travelling through the Atlantic ocean with a large fetch
Formation of West Cork, Ireland
DC
- Limestone eroded by waves but also verticle fluvial processes in the past creating a river valleyin the Bantley Bay coastline - (now inundated)
- As sea levels have risen, the river valley has been submerged - making the bay long and narrow
- Rivers eroded the softer rocks to form valleys
- Rising sea levels drowned the valleys
- Since then, marine erosion has continued to erode headlands and bays forming a Ria
Cliffed coast description
- The transition from land to sea is abrupt
- At low tide , the forshore zone is exposed as a rocky platform
- The cliffs are vertical and usually made of igneous, granite, basalt or older and compacted sedimentary rocks
Sandy coast description
- At high tide, the sandy beach is unundated, but vegetated dunes are not
- Consists of younger, weaker sedimentary rocks (e.g chalk, clay, sandstone)
- Dune vegetation stabilises the coast and prevents erosion
Estuarine coast description
- Extensive mudflats, cutting channels are exposed at low tide but inundated at high tide
- Closer to backshore, the mudflats are vegetated forming a saltmarsh
Where are estuaries found?
Estuaries are found at the mouth of a river
Definition of Dynamic Equillibrium
The balanced state of a system when inputs and outputs balance over time. If one element of a system changes because of an outside influence, the system adjusts to the change and equillibrium is regulated.
The order of the littoral zone
Backshore, Foreshore, Nearshore, Offshore
Submerged coast
A coast that is flooded by sea due to rising sea levels of subsiding level.
Strata
The different layers of rock within an area and how they relate to each other
Why are dips important in understanding cliff profiles
They impact how the geology is exposed impacting erosion
What is the bottom geology of the dips called?
Bedding planes
What is the position of the littoral zone affected by?
- Waves
- Tide
- Weather
- Seasonal storms (short term)
- Mass movement
- Climate change (long term)
- Sea levels rising
- Erosion / weathering
What does the resistance of rocks depend on?
- How reactive minerals are in the rocks when exposed to chemical weathering
- The degree to which rocks have cracks / fractures and fissures which are weaknesses exploited by weathering and erosion
- Whether rocks are clastic or crystalline - clastic rocks have higher rates of erosion
Emergent coasts
Where the coasts are rising relative to sea level (e.g due to tectonic up-life)
Submergent coasts
Are being flooded by the sea either due to rising sea levels and / or subsiding land.
Horizontal dip:
Vertical / near vertical coastline with notches reflecting strata that are more easily eroded.
Seaward dip: (high angle)
Sloping low angle profile with one rock layer facing the sea. Vulnerable to rock slides down dip slope.
Seaward dip: (low angle)
Profile may exceed 90 degrees, producing areas of overhanging rock, very vulnerable to rock falls.
Landward dip:
Steep profiles of 70-80 degrees, producing a very stable cliff with reduced rock falls.
Faults
Major weaknesses within rock layers in the Earth’s crust, often due to significant movement.
Joints:
Fractures/cracks in the Earth’s crust along with where has been no significant movement parallel to the fracture plane
Fissures:
Narrow/elongated cracks in rock or openings in the Earth’s crust. Erosion can exploit these cracks.
Folding:
When rocks experience compressional forces that cause them to bend and warp.
This can be a result of tectonic plate movement.
Folding can lead to opening up joints in rock.
How are caves formed?
Erosion of weakened rock along faults
How are arches formed?
Where two caves on either side of a headland join up
How are wave cut notches formed?
Erosion of weak rock as cliff base
How are stacks and stumps formed?
Pillars either fault bounded or made of more resistant rock
Example of concordant coast lines
Dalmatian coast Croatia, west cork coast Ireland
Examples of discordant coastlines
Gower coast south wales, east coast Purbeck
Describe the essential features of backshore (3)
- A part of the beach above normal high tide mark, at cliff base.
- Only effected by the sea during exceptionally high tide and storms. – Consists of features like storm beaches, pebbles and berms
Describe the essential features of foreshore (3)
- Lower beach, intertidal or surf zone.
- An area with a high water mark and a low water mark.
- This area is most important for marine processes in times influenced by waves and by storms.
Describe the features of nearshore (2)
- Shallow water close to the tide line but covered by water at normal low tides.
- The zone in which waves usually brake.
Describe the features of offshore (3)
- The point beyond the influence of waves where there is little to no impact of the sea bed.
- Activity in this areas is limited to deposition of sediment.
What causes waves?
Waves are most commonly caused by wind. Wind-driven waves, or surface waves, are created by the friction between wind and surface water (frictional drag). As wind blows across the surface of the ocean or a lake, the continual disturbance creates a wave crest. The gravitational pull of the sun and moon on the earth also causes waves.
What is shoaling?
Process that decreases water depth-
It occurs as waves enter the shallow water, the wave speed and wave length decrease in shallow water, therefore the energy per unit area of the wave has to increase, so the wave height increases.
Features of destructive waves
- Large wave height and short wave length.
- They have tall breakers that have high downward force and strong backwash.
- Their frequency is high between 13 to 15 waves per minute.
- Their strong downward energy helps erode beach material and cliffs.
- The strong backwash results in narrow beach profiles.
Features of constructive waves
- Flat and low in height and have a long wave length.
- Their strong swash carries material up the beach, forming a berm.
- They have a low frequency of between 6 and 8 waves per minute. –
- The wave energy dissipates over a wide area which results in a weak back wash.
Describe the essential features of coastal flood planes
Low lying and with low relief
Often contain wetlands and marshes usually formed by the deposition of the land sediment or by a fall in sea level exposing the former sea bed
Explain what a Haff coastline is (2)
- Type of concordant coastline found along the southern shores of the Baltic sea.
- Long sediment ridges (including spits) topped by sand dunes that run parallel to the coast just offshore, creating haffs (lagoons) between the ridges and the shore
What are the inputs to the coastal system?
- Marine (waves tides storm surges)
- Atmospheric (weather climate solar energy)
- Land (rock type and structure tectonic activity)
- People (human activity coastal management)
The different processes on coasts
Weathering, mass movement, erosion, transport, deposition
What are the two main types of coastline?
Rocky and sandy coastline
Name the different geological structural features?
Joints, fissures, folds, fractures
Permeable
Porous. Water can absorb into the rock
Examples of igneous rock
- Granite
- Basalt
- Dolerite
Examples of metamorphic rock
- Slate
- Schist
- Marble
Examples of sedimentary rock
- Sandstone
- Limestone
- Shale
What is the lithology of igneous rock?
They are crystalline with interlocking crystals
What is the structure of igneous rock?
Rocks such as granite have a few joints so there are limited weaknesses
What is the erosion rate of igneous rock?
Very slow. The interlocking crystals make for strong, hard erosion-resistance rock.
Rocks such as granite have few joints, so there are limited weaknesses.
What is the lithology of metamorphic rock?
Crystalline. Many exhibit a feature called foliation, where crystals are all orientated in one direction (producing weaknesses)
What is the structure of metamorphic rock?
They are often folded and heavily fractured
What is the erosion rate of metamorphic rock?
Slow. They are resistant to erosion. Many exhibit a feature called foliation, where crystals are all orientated in one direction (producing weaknesses). They are also often folded and heavily fractured, which are weaknesses that erosion can exploit.
What is the lithology of sedimentary rock?
Clastic and are younger than igneous and metamorphic rock.
What is the structure of sedimentary rock?
Tend to have many bedding planes and fractures e.g shale. The weakness materials is known to be unconsolidated sediment. However, some limestones and sandstones are actually crystalline sedimentary. They have been compressed and compacted over hundreds of millions years.
What is the erosion rate of sedimentary rock?
Moderate - fast. Geologically younger rocks are weaker and therefore erode faster.
Formation of the Dalmation coast:
- Tectonic forces produced by the collision of African and Eurasian plates compressed Carboniferous Limestone during the Alpine Orogeny 50 million years ago.
- This created up folded ridges (anticlines) and down folded valleys (synclines) aligned parallel to the coast
- Sea level rise at the end of the Devensian Glacial overtopped the low points of the anticlines and the sea flooded synclines
- This produces lines of narrow islands parallel to the coast formed by projecting sections of anticlines.
Why are coasts difficult for vegetation to grow?
- Because coasts are high saline / salty environments so vegetation needs to adapt and it leads to plants becoming inundated
- There is a lack of hummus (dead, organic materials) so soil lacks nutrients
- Destructive waves / storms could damage vegetation
- Erosion can damage plants
What is the importance of vegetation at the coast?
- Provides shelter/habitat for organisms (coastal species)
- Help add nutrients to sand by litter (due to decomposition when the plants lose their leaves and die)
- Roots of vegetation stabilise sand and soil, reducing the rate of erosion, as landscapes become more stable (roots bind sediment particles together)
- Prevents flooding by providing a barrier between land and sea
- When submerged, plants growing in sediment provide and protective layer, the surface of the sediment is not directly exposed to moving water and therefore erosion.
- Plants protect the sediment from wind erosion by reducing speed at the surface.
Pioneer species
Highly adaptive to challenging environments. They allow less adapted species to colonise the area creating a climal community.
What happens as Pioneer species die
They die and drop off organic material, making the soil more nutrient dense, allowing more dense vegetation to grow
Plant succession
The evolution of plant communities at a sight over time - from pioneer species to climate vegetation
Halosere
Mud flat / salt marsh environment, inundated
Psammosere
Sand dune environment, dry
Xerophytic
Plants adapted to incredibly dry environments with very little nutrients (deep roots, leaves with small surface area to reduce water loss) e.g marram grass which have roots up to 3m deep.
Halophytic
Plants adapted to survive in environments with high concentrations of salt, thrive in hacoseres. (e.g Samphire)
Why is plant succession so important in Haloseres and Psammoseres?
- The roots of pioneer species stabilise the sediment, preventing it from erosion
- Decomposition of pioneer species allows more nutrients in the soil, allowing for colonisation of less adaptive plant species
What are the similarities and differences between the two ecosystems?
- Halosere environments are inundated whereas psammoseres are very dry
- Psammosoes have a lack of nutrients whereas haloseres have an abundance of nutrients
- Both have plant succession occuring
- Both have coastal accretion
- Both are in low energy environments
Foredune
An object such as a plant or rock causes sand to build up on the lee side
Mobile dunes
Plants begin to bind sand together
Semi-fixed dunes
The dunes could be 20m high here
Dune slack
Once a hollow is formed, perhaps by a blowout, sand is removed by the wind until the damp sand rear the water table cannot be transported
Explain the formation of embryo dunes
Early accumulations of sand at the back shore where dry sand is blown on shore at low tide and accumulates around rocks and wood. these accumulations are prone to wind and wave erosion during storms
What are dune slacks
At high tide or under storm conditions, sea water may reach dips in the sand dunes, called slacks and collect. blow out caused by strong winds stops when it reaches damp sand at the water table as damp and is less easily blown away.
Apart from colour what distinguishes yellow dunes from grey dunes
Grey dunes are older with fixed by developing vegetation and have a higher humus content. grey dunes tend to be more acidic. due to the grater vegetation cover and roots from the vegetation mean they are more stable.
What is mass movement
The downslope movement of rock, sediment and soil under the influence of gravity
Bedding planes
Horizontal cracks that are natural breaks in the the strata, caused by gaps in time during periods or rock formation
Why is marram grass important for the formation of sand dunes
Effective in stabilising blown sand and acts as a natural buffer to erosion of the areas behind it. flexible waxy leaves which can cope with harsh environment of the coast (water deficient environment). it has roots up to three metres long so can reach water far below the surface and also the anchoring roots provide strength and stabilising properties.
What is long shore drift?
The transportation of sediment along the coast by action of the waves, often in the same direction of the prevailing winds. where waves approach the coast at an angle, the swash of the breaking wave is directed diagonally up the beach.
However, the backwash of the returning water runs directly down the beach and a right angle under the force of gravity
Explain why estuaries are ideal for the development of salt marshes (6)
They are normally sheltered stretches of water and the lack of strong waves, this encourages the deposition of mud silt. sediment is supplied to an estuary by its river. this is added to by the marine sediment flowing into the estuary at high tide. mudflats are gradually built up in the sheltered water and they will eventually be colonised by the pioneer plants. those plants prosper in the sheltered conditions and help trap more sediment. so the plant succession is set in motion.
What is the final stage of salt marsh succession called?
Climax Vegatation
What is the correct order of plant succession of a sand dune?
Embryo dunes, foredunes, yellow dunes, fixed dunes, health/woodland
How does vegetation stabilise sediment?
As the roots of vegetation bind sediment particles together, stabilising the sand and soil to become more stable, reducing the rate of erosion.
When submerged, plants growing in sediment provide a protective layer, so the surface of the sediment is not directly exposed to moving water and therefore erosion.
Formation of bays:
Disconcordant coastlines have headlands which are consisting of hard, resistant rock such as granite, and have very slow rates of erosion. They also consist of alternating layers of less resistant rock such as sandstone which is more easily eroded. The softer rock is eroded, leaving the hard bands of rock uneroded, forming a bay.
Sand dune succession formation:
1- Begins with colonisation of embryo dunes by pioneer species. They stabilise mobile sand with their root systems.
2- Embryo dunes alter environment conditions from harsh salty mobile sands to environment conditions from harsh salty mobile sands to environment other plants can tolerate
3- New plant species colonise embryo dunes creating foredunes
4- Soil develops, nutrients/water become more available so plants that had better conditions can concieve the area.
5- Dune slacks: periods of raw erosion can create low areas
6- Foredunes become more stabilised and grow to yellow dunes
7- Other species are introduced, e.g marram grass, eventually grey dune forms
8- New embryo dunes form as long as there is a supply of sediment returns, this protects original dune, allowing vegetation.
Salt marsh succession:
1- Starts in low energy environments, e.g estuaries since they are sheltered from strong waves so sediment can be deposited
2- Algal stage: (e.g blue green algae) grow on and within bare mud, binding it together
3- Pioneer stage: (e.g glasswart) roots begin to stabilise the mud allowing further mud acretion
4- Establishment stage: (e.g Salt marsh grass) a continous carpet of vegetation is established and the salt marsh height increases
5- Stabilisation: (e.g Sea lavender): this area of salt marsh is rarely submerged
6- Climax vegetation: (e.g rush, sedge): developed soil profile and only submerged for x2 each year.
Example of Algal stage
Blue green algae
Example of Pioneer stage
Glasswart
Example of Establishment stage
Salt marsh grass
Example of Stabilisation (plant)
Sea lavender
Example of Climax vegetation
Rush, sedge
Morphology
Features and landscapes. The result of coastal processes.
Retreating coast
Erosion > deposition
