Coasts

What are coasts

Where sea and water interact. Influenced by terrestrial processes(erosion, deposition), human factors(pollution and settlements) ,marine processes(tidal and waves) and atmospheric factors(climate and storms)

What’s fetch

Distance of open water which a wave has passed

What are main type of waves

Constructive and destructive

What are types of erosion

Hydraulic action, abrasion, attrition and corrosion

What are types of sub aerial processes

Mass movement and weathering

What are types of transportation

Saltation, traction, suspension and solution

What’s attrition

Materials carried by waves so they bump into each other and become smoother and smaller

What’s hydraulic action

Water forced into cracks of coastline so air expands in rocks causing minor explosion

What’s corrosion

Acid in salt water slowly dissolves rocks on coast like limestone and chalk

What’s abrasion

Coast is worn down by material carried by waves which through rocks against coast at high velocity

What landforms are erosion all

Cave, headland , arch, stack and stump

What landforms are depositional

Beach, tombolo, barrier spit, lagoon, bay barrier, wave cut platform, wave built terrace

What’s the littoral zone

Area of the coast that can be affected by wave action

What’s the function of a beach

Acts as a barrier between land and sea

Back shore in a littoral zone

Not affected by wave action but can be in storm events.

Fore shore in littoral zone

Intertidal area between high and low tide

Nearshore in littoral zone

Breaker zone because friction between seabed and waves causes them to break

Offshore in littoral zone

area outside of wave action

What are storm beaches

Highest berm left by storm waves during spring tides(highest due to gravitational pull of moon and sun). Sediment is thrown up by the large waves and remainS. More common in shingle beaches affected by destructive beaches.

What are the long term factors that affect coasts

Geology like rocky type and structure. Coasts can be classified as rocky, sand or estuarine as well as concordant or discordant.

Sea level changes due to global warming or tectonic activity as plates move up and down during earthquakes. Eustatic and isostatic changes in sea levels leading to submergent or emergent landforms

What are rocky coasts

more resistant geology so steeper cliffs. High energy environment so has more erosion

What are coastal plain landscapes

Low relief land that slopes towards the sea. Can be sandy or estuarine coastlines. Form due to coastal accretion as it’s a low energy environment so more deposition occurs than erosion. Has dunes as well as wetlands and salt marshes due to poor drainage.

What’s the role of dunes

To stabilise coasts and reduce erosion

How do short term factors affect coasts

High or low tides. Destructive or constructive waves, storm events. This causes coasts to retreat or advance depending on rates of deposition and erosion. Can create low or high energy environments

How are estuarine coasts formed

Formed at the mouth and made of and and silt

What are berms

Formed as sand or shingle slowly move up the beach by successive incoming tides. Common in shingle beaches

What’s difference between high energy coasts and low energy coasts

What are cusps and how are they formed

Semi circular shapes along a beach formed when outgoing rip current and incoming waves set up nearly circular water movements.

What’s wave refraction

Bending of waves caused by reductions energy. As waves approach they’re refracted so energy is concentrated around bays and can cause coves . Energy decreases as water depth increases.

Classic sediment

Comes from weathering of rock and varies from very small clay particles to sand pebbles and boulders.

Biogenic sediment

Skeletons and sediments of marine organisms

Non cohesive sediment

Larger particles moved grain by grain like sand

Cohesive sediment

Small clay and mud particles bond together

How does sediment move around the UK coast

In sediment cells also known as littoral cells

What’s the difference between weathering and erosion

Erosion- breakdown and movement of rock by water or wind

Weathering is the breakdown in situ of rock( mechanical, chemical and biological

What is mechanical weathering

Or crystallisation . Sea water forced into cracks of rocks by waves. Water evaporates leaving salt behind and so salt crystals grow fracturing rock further and causing it to break down

What’s chemical weathering

Rain is slightly acidic which reacts with weak minerals causing rocks to dissolve and decay limestone and chalk

What’s biological weathering

Vegetation roots grows into cracks of rock and split the rock apart

What’s rock fall

Sudden form of mass movement. Rock fall occurs when fragments of rock weathered from cliff face fall under gravity and collect at base

What’s rotational slumping

Mass movement- bottom of cliff is eroded by waves so slope is steeper and cliff slides downards in rotation. Caused by saturation of rain making it heavier and lubricating it

What’s lithology

Physical properties of a rock such as its resistance to erosion.

Hard rock like granite are resistant to weathering and erosion so erodes at 1mm per year

Soft rock like limestone are more susceptible to erosion and weathering so erodes 2.5mm

What are concordant coastlines

Layers of rocks parallel to coast e.g Lulworth cove. Hard rock like limestone acts as a barrier for soft rock like clay so erosion is slow but if there’s a fault marine processes take place exposing soft rock. Eroding of soft rock occurs until another band of hard rock is reached, this creates a circular shadow in coastline called a COVE

What’s discordant coastline

Layers of rock are perpendicular to coast e.g Swanage bay

Different types of rocks exposed to marine processes at same time but soft rock will erode faster. Differential erosion creates headlands where rock is more resistant and bays where it’s less resistant. Waves refract and energy is focused on ends of headlands creating caves arch stack and stumps with wave cut notches and platforms

What are examples of concordant coastlines

Dalmatian and haff coastlines as well as lulworth cove in Dorset UK

Formation of Dalmatian coast

Concordant coastline Found in Croatia. Formed by tectonic activity and sea level rise. Tectonic activity created anticlines which are upward folds in rock strata and sync lines that are downward folds on rock strata. Sea level rise in devensian glacial period flooded synclines so anticlines only emerge out of water. Resulted in islands running parallel to coast.

Formation of Haff coast

Created by deposition of unconsolidated material. Melted ice sheets deposited thick layers of gravel on tundra plains. As sea levels rose constructive waves pushed sediment landwards. Sand or gravel ridges formed across bays and river mouth trapping river water behind them creating lagoons. Formed along Baltic coastline

Micro features

Rock formation and tectonics leads to anomalies forming within rocks, creating areas of weaknesses leading to more rapid erosion and weathering, like joints folding and faults

What are joints

Micro feature- vertical cracks caused by tectonic movement and contraction

What are folding

Micro feature- rocks under pressure due to tectonic movement and becomes folded without breaking

What are faults

Micro feature -pressure fractures rocks and is very sudden and causes earthquakes.

What effect does micro features have on coastal topography ( arrangement of an area)

Affects weathering and erosion rates and thus cliff profiles

What are cliff profiles

The angle and height of the cliff face including any features and is dependent on lithology.

What are three types of cliff profiles?

1. Uniform horizontal layers of rocks

2. Rocks dip gently seaward with near vertical joins

3. Rocks dip inland so steep stable cliff

What is coastal recession

It is the rate of recession which is the speed at which the coastline is moving inward. Mainly caused by lithology.

What are igneous rocks?

Slowest erosion rate with 0.1cm a year.

Crystalline structure interlocking so more resistant.

Fewer joints.

E.g granite basalt, dole rite

What are metamorphic- foliated rocks

Slow erosion rate with 0.1-3cm a year.

Causes folation when crystals rearrange and line up facing the same direction

Often folded and fractured creating faults.

E,g Slate, shale, Schist

What are metamorphic-non foliated rocks

Slow erosion rate with 0.1-3cm . Metamorphism causes grains to recrystallise into a very solid interlocking network. These rocks are resistant and again folding and faulting makes them less resistant than igneous rocks

What are sedimentary rocks

Fast erosion rates with 5-10cm a year. Most are clastic(made up of broken pieces of older rocks). Younger rocks weaker than older because they haven’t been compressed long enough so more reactive . Bedding planes and joints make them even more vulnerable to recession e.g. sandstone, limestone, clay

Types of lithology- unconsolidated material

Sediment has been cemented to make solid rock(lithification)

Types of lithology- pore water pressure

Internal force within cliffs exerted by groundwater within them(in interstitial gaps). Pores affect how permeable a rock is

What does periglacial mean

Periglacial areas are next to glaciers. If still cold they have permafrost making cliffs resistant. If ice has retreated the me,ted water will wash unsourced material on land

What’s continuous permafrost

Coldest region. 1500m depth, no melting of surface layer. E.g Siberia

What’s discontinuous permafrost

Surface layer melt in summer which is the active layer so lots of water is released. Slightly warmer region like in north Canada. 20-30m deep.

what’s sporadic permafrost

0 degrees. Isolated spot. Cold and minimal thawing.

What are coastal vegetation

They act as stabilisers and roots bind sediments together.

What are submerged plants and surface level plants

Submerged plants are protective layers against moving water. Surface level plants are plants protecting sediment from erosion of wind. They are protected by sand dunes,salt marshes, coral reefs, mangroves.

Plant adaptation- halophytes

Salt tolerant e.g mangroves grown in water

Plant adaptation- xerophytes

Drought tolerant- salt water is drying and sand doesn’t retain water. E.g marram grass

Plant adaptation- Psammophytes

Grown in wind blown sand, tolerates dry salty conditions and being buried e.g sea holly

Key concepts for plant communities

1. Plant succession-changing structure of a plant community over time as bare sediment is colonised . Each step in change is called a serial change

2. Zonation- how ecosystems change spatially away from the shoreline

3. Pioneer species- first hardy species to colonise areas of exposed sediment

4. Climax communities- final stage of succession with greatest biodiversity.e.g woodlands in uk

What are sand dunes and where are they found

Sand mounds formed by wind blowing wind over each other

What are salt marshes

Low energy environment. Tides and rivers bringing sediment in and out and as small particles are deposited they stick together. These sediments are then colonised by algae ,pioneer species .

What are waves

Friction between wind and water. Energy from wind transferred to water

What factors impact size of wave

Wind strength, fetch, water depth, time of wind blowing

Wave period

Time taken for two crests to pass a given point

What’s the wavelength

It’s the product of waves velocity and period

How are waves formed

1. At sea waves move in circular motion ,energy moves not water,

2. When water is deep, there’s very little motion

3. When the sea gets shallow, wavelength shorten and friction slows base of wave but the top moves faster

4. The water now moves in elliptical motion

5. This makes the water move to shore so wave breaks

Difference between constructive and destructive waves

Why do constructive waves encourage deposition

Long wavelengths and low frequency which prevents erosion as no sediment is taken into sea.Lack of a breaker component so waves spill and move up a beach to deposit materials. Weak backswash and suppressed wave gradient means no sediment is carried into sea

Why do destructive waves encourage erosion

Short wavelength and high frequency leads to erosion of sediment in sea because there’s more water to transport. Has a breaker so plunges at beach when a height is reached so they don’t travel up a beach.

What’s the seasonal variation of beaches

In winter, with rough weather, sand is stored offshore

In summer with calmer weather sand is stored at the beach

How are wave cut notches and wave cut platforms formed

Waves break at foot of cliff so eroding it, creating a wave cut notch. The rock above notch becomes unstable and collapses. Attrition and transportation removes rock debris.The cliff retreats leaving behind a wave cut platform

How are arches formed

2 caves next to each other on headland join as erosion widens the base.

How are stacks and stumps formed

Arches collapse leaving isolated pillars of rocks which are eroded further into stumps

How are caves formed

Joints faults eroded by hydraulic action and abrasion. Blowhole made when overlapping rock is collapsed and cave opens at ground level.

Define beach morphology

Profile of the beach(steep/shallow slope) concerned with the movement of sediment caused by wave action

What’s the beach morphology of summer and winter beaches FINISH WITH PPT

Summer: low energy constructive waves, steep beach angle, large particles at back of beach. Berm ridges

Two types of deposition

Flocculations- smallest sediment like clay stick together so they become heavy enough to sink. Last to sink

Gravity setting- heaviest largest sediments deposited first

What are the impacts of seasonal change on beach morphology

Creates summer or winter profiles due to variations of wave activity.

Sediment is dragged offshore by destructive waves in winter and returned by constructive waves in summer. Summer as steeper slopes than winter.

Define beach profiles and what are they dependent on?

Landscape of beach both and below water. Describes distribution, shape, size, type of sediment deposited. They are dependent on distance from shoreline

what’s the significance of distance from the shoreline in beach profiles

Fine shingle particles along drift aligned beaches are carried away by LSD so becomes rounded as they move

Where are coastal deposition found at and what causes them

Occurs in low energy environments so have reduced effects of waves ,tides and currents.

They are caused by waves losing energy as they slow down so dropping sediment

How does erosion and deposition occur with waves

Moves sediment up and down the beach in the direction of wind(LSD)

How does erosion and deposition occur with tides

Determines where erosion takes place

How does erosion and deposition occur with rip currents s

Takes sediment from offshore to nearshore

How does erosion and deposition occur with other currents

Takes sediment from offshore to onshore or vice versa

Define Longshore drift and the factors affecting it

Movement of material along a coast by waves which approach at an angle to the shore but recede directly away from it. Factors: geology, rivers, tides, simonant wint, prevailing wind(most common wind), shape of coastline- refraction, man made obstacles(sea defenses)

How does the greatest rate of LSD occur

When waves approach coast at 30 degrees angle.

How does swans and backswash work in LSD

Awash carries material up beach in direction of wind and backswash carries sediment back to the sea at right angles