Coasts EQ2 Flashcards
What is weathering?
Chemical : slightly acidic rainwater easily dissolve calcie minerals in limestone. It trickles into joints and cracks and erodes the rock.
Physical : freeze thaw and exfoliation (expansion and contraction due to temprature changes which creates cracks and peel off thin layers of rock)
What is mass movement?
Non marine processes seen on cliffs like slumping or soil creep or landslides.
Caused by gravity but worsened by rainwater.
How are waves formed?
Waves are formed by the transfer of energy from the wind to the sea.
Friction between water and wind creating ripples in the water. This is a domino effect that makes them larger and larger.
Characteristics of a constructive wave?
Long Wave Length
Low in height
Strong Swash deposits sediment up the beach
Lower Freq (6 a minute)
Backwash soaks into beach
LOWER ENERGY
associated with Summer
Characteristics of a destructive wave?
High energy
winter
Backwash claws at beach - bringing sediment down.
Weak swash
Higher frequency
short wave length
Explain what happens to the characteristics of a wave as it approaches the nearshore?
As a wave approaches the nearshore, its height increases and its wavelength decreases. The wave slows down due to friction with the seabed, causing the wave to become steeper and eventually break.
Define beach morphology
The shape and appearance of the beach profile. Can change depending on erosion, deposition , human activity and transportation.
Factors causing beach profiles to change in the long term
Isostatic readjustment
destructive waves can form bars or ridges
Discordant coasts
Sediment supply from rivers could reduce if Dams are constructed
TGS
Vegetation
Factors causing beach profiles to change in the short term
Daily Tides - low tide = longer profile — high tide = shorter profile (more beach is covered cliffs are closer together)
Currents
Alignment of the moon / sun / Earth
Tsunamis
Desribe Moon Tides:
Spring Tides: Occur during full moon and new moon when the Earth, moon, and sun align, causing higher high tides and lower low tides.
Neap Tides: Occur during first and third quarter moons, causing lower high tides and higher low tides.
When the moon is closest to Earth, its gravity pulls water, creating a high tide on the side facing the moon and the opposite side beacuse the Earth “creates more space”. The areas perpendicular to the moon have low tides, creating two high tides and two low tides.
4 main transportation proccesses:
- Traction: Large rocks and pebbles are rolled along the seabed.
- Saltation: Smaller particles are bounced along the seabed.
- Suspension: Tiny particles are carried by the water, floating.
- Solution: Soluble materials, like minerals, are dissolved in the water.
How does Long Shore Drift work?
Longshore drift moves sediment along the coast. Waves hit the shore at an angle, carrying sand up the beach (swash). Gravity then pulls the water back down (backwash), moving the sand in a zigzag pattern along the shoreline.
The strongest LSD occurs when the waves approach the coast at 30 degrees to the coast. - the dominant wind will determine the direction of LSD.
Two types of beaches regarding LSD:
Swash aligned beach - wave crests approach parallel to the coast so there is no movement of sediment - results in bay head beaches and offshore bars.
Drift aligned beach - wave crests break at an angle to the coast so there is consistent LSD. creates spits, tombolas, cuspate forelands and bars.
What is Terminal Groyne Syndrome?
Where the removal of sediment > supply - erosion occurs.
E.G seaford
It interrupts the natural flow of sediment and the area furhter down the stream isn’t replenshed.
What are some depositional landforms?
Beaches
Spits - extended stretches of sand that go beyond the coastline.
Offshore Bars - Submerged ridges of sand or coarse sediment deposited beyond the shoreline by currents and wavves.
barrier beaches - connected spit on both sides -forms a lagoon.
Tombolos - ridge formed in between an island and the coast from LSD.
Cuspate forlands - triangular shaped headland that extends out of the coast.
These landforms are made from unconsolidated sediment meaning they are vulnerable to change. _ they can be stabilised by vegetation however.
What is Gravity settling and Flocculation?
Gravity settling - The energy of transporting water becomes too low to move sediment so it essentially gets stuck.
Flocculation - Where very small particles clump together due to attraction and become large enough to sink.
The amount of unconsolidated sediment in a coastal system is called the sand budget - and determines the number of depositional features.
What is a sediment cell?
A closed system where movement of sediment is largely contained within its boundaries. There are inputs (sources) like erosion or from rivers tranfers like LSD or saltation and stores which are either temporary like depostional landforms or permanant.
11 in England and Wales.
What is Physical / Mechanical Weathering?
- Physical (Mechanical) Weathering: The breakdown of rocks into smaller pieces without changing their chemical composition, often due to temperature changes, freezing and thawing, or pressure release. Salt crystalisation where salt form in cracks exerting pressure on them.
What is Biological Weathering?
- Biological Weathering: The breakdown of rocks caused by living organisms, like plant roots growing into rocks, or animals burrowing into them.
What is Chemical Weathering?
- Chemical Weathering: The breakdown of rocks due to chemical reactions, such as oxidation (rusting) or dissolution, where minerals in the rock react with water or air.
What are subaerial processes?
Subaerial processes are land-based processes and occur above the waterline. They include weathering and mass movement.
How do Constructive waves affect beach morphology?
They cause net movement of sediment up the beach - steepening the beach profile.
Swash carries sediment of all sizes up the beach, but weaker backswash can only transport smaller particles down the beach.
This leads to a sorting of material in the foreshore zone. Since the Backswash flows down the beach and loses energy through friction and depletion of water through percolation, sediment is further sorted as coarser sands are deposited in the middle of the beach.
Desribe the changes to beach morphology between Summer and Winter
Summer - Constructive waves, sloped beach profile forms Berms.
Winter - Destructive waves, flatter profile.
What is a berm?
A flat strip of land, raised bank or terrace formed due to landward transport by swash.
How do destructive waves affect beach morphology?
Cause net movement of sediment down the beach. This reduces the beach gradient. Strong backwash erodes material from the top of the beach carrying it to the offshore zone.
What is Abrasion?
When waves pick up beach material and hurl them at the base of the cliff. The more energy a wave has, the more effective it will be.
What is Hydraulic Action?
Hydraulic action is a type of coastal erosion where the force of water (from waves) traps and compresses air in cracks in cliffs. When the wave retreats, the compressed air expands explosively, weakening the rock and causing pieces to break off.
What is Solution / Corrosion?
Acids contained in sea water and rain will dissolve carbonate rocks such as limestone. Also when salt crystals are deposited in cracks over time, the salt accumulates and applies pressure to the crack.
What is Attrition?
This does not erode a coastline. Waves smash rocks and pebbles against eachother, they break and reduce in size.
Explain how Erosional Processes are influenced by wave size and lithology?
🔹 Lithology – Resistant rocks (e.g., granite) erode slowly, while softer rocks (e.g., clay) erode quickly due to weaker structure and faster weathering.
🔹 Constructive Waves – Low energy, strong swash, weak backwash; deposit more material than they erode, leading to beach buildup.
🔹 Destructive Waves – High energy, weak swash, strong backwash; erode coastlines rapidly through hydraulic action, abrasion, and attrition.
4 key types of mass movement
Rockfall
Slumping
Mudflows / Lahars
Rockslide
What factors affect shear stress (risk of mass movement)
Water content
Slope Angle
Faults, folds or fissures
Lack of Vegetation binding
Unconsolidated rock
Extent of weathering
Burrowing of animals
How does Slumping occur?
Saturated Conditions. Softer material lies on top of more resistant, impearmable rock.
What landforms are created from mass movement?
Terraced Cliff Profiles - Like a “steps” formation after rockfall or slumping.
Rotational Scars - Fresh, unvegetated scar on the cliff face after slumping.
Talus Scree Slopes - A fan of material at a cliff foot from rockfall (usually smaller sediment).
What is a geo?
A geo is a narrow, steep-sided coastal inlet formed by wave erosion along a line of weakness, such as a fault, joint, or crack in the rock.
