•Coasts 3 Flashcards
What is an example of a fast process?
Longshore drift
Deposition
What is an example of a slow process?
Weathering
Why have we had major fluctuations?
Over the past 2 million years as a result of glaciation
What is an instantaneous scale?
Landforms that are affected by changed operating within a single cycle so within seconds to days to weeks
What are event time scales?
Ones that operate across a time span from an individual event through to seasonal variations which may take place from a few days to a few years
What is an engineering time frame?
When fluctuations take place over longer fine scales ranging from years to decades and centuries
What is a geological time scale?
From decades to Millenia as change takes place in sea level and climate
What is an example of an instantaneous landform?
Beach
What is an example of an event landform?
Sand dune
What is an example of an engineering landform?
Stack
What is an example of a geological landform?
Spit
What will influence the rate of change at a coast?
Fetch Waves Tides Wind Mood Prevailing wind
When did the last ice age end?
11,500 years ago
What is the process of a stack?
Wave-cut notch formed by erosion such as wave pounding which creates weaknesses in rocks
Caves form by further erosion such as wave quarrying
Arch formed from undercutting where erosional processes such as hydraulic action have occurred
There are weaknesses caused by weathering e.g solution
Sub-aerial processes occur on top of the cliff
Stack formed as weathering processes like carbonation cause an arch to collapse
Cliff recession is caused by erosion and slumping
A wave-cut platform is exposed at low tide
What does vertical erosion create?
Blowholes
How does a spit form?
Longshore drift carries a supply of sediment along the shoreline
Where the coastline changes direction, material is deposited in the open sea by longshore drift
Material accumulates over time so that it lies above the level of the water and a spit develops
Vegetation begins to grow, Helios from to colonise the spit
The end of the spit it shaped by waves from other directions so that it forms a hook
If sediment continues to be supplied, the spit may grow beyond the hook
What is a tombolo?
A spit joining an offshore island to the mainland
What is a barrier Island?
Barrier islands as found in seas with shallow gradients close to the shore
They form as a result of deposition by constructive waves
Formed in areas where tidal ranges are low
Formed parallel to the shoreline
What are the reasons for the location of the formation of barrier islands?
The accumulation of material transported by swash or wind-blown sand
The isolation of the shore when sea levels rise; higher storm beaches and sand dune ridges are left isolated
The emergence of previously submerged offshore bars as sea levels fall
Spits being heavily built up by storm waves but then breached, forming a series of islands
Why can a bar only form across a bag with no major flow?
Because the energy from a flow will move sediment and stop it from being deposited as deposition will only happen in calm water
Why might bars in the Uk be made of flint?
There is flint on the floor of the English Channel which will have been washed up during sea level change 6,000 years ago
What is a cuspate foreland?
A low-lying, almost triangular area of coast where sediment is deposited
What are the reasons for the formation of a cuspate foreland?
Waves from different directions create two converging spits
Deposition of sediment from fluvial sources causes a build-up of material
Changes in coastline over thousands of years have led to changing patterns of deposition
What is the difference between a ridge and a runnel?
Runnels run at right angles to the directions of maximum fetch
What is a berm?
A ridge of material running across the back of a beach
What determines the position of a berm?
The highest line on a beach that a wave has reached
What is a beach cusp?
A crescent-shaped indentation on the seawards edge of a berm
Where is a storm beach found?
On the upper shore
How does the gradient change as you move inland?
The gradient gets steeper
Why does gradient get steeper with larger particles?
Coarser sediments are more permeable so less water is available for backwash
What are sand dunes?
An aeolian feature that form when: Large tidal ranges allow sand to dry out Gradient of land is relatively flat There is sufficient space There is a stabilising agent There is a large supply of sand
What is saltation?
Sand grains are picked up by the wind and bounced
What is suspension?
Lighter grains and picked up and carried by the air before being deposited
What is surface creep?
Traction type process
Grains are rolled along the land by the wind
What is the first type of dune and how long do they take to develop?
An embryo dune
10-20 years
What has happened to sea levels?
Over time they have fluctuated but recently there had been a general trend of sea level rise
What is isostatic change?
Caused by the level of land changing
Local
What is eustatic change?
Caused by a change in the sea level
Global
What is a change in sea level due to glaciation called?
Glacial-eustacy
In the Devensian glacial period (the most recent ice age 100,000- 11,000 years ago) what were sea levels like?
100- 125m lower than today
Most of the continental shelf was dry land
What is transgression?
When coastlines retreat due to sea level rise
What is regression?
When coastlines advance as water gets locked up in ice sheets and glaciers
What is the change in the level of land due to glacial processes called?
Glacial-isostacy
As ice melts, how much can land rise by each year?
20 mm per year
Where are fold mountains found?
Subduction zones and constructive plate boundaries due to tectonic uplift
The process is called orogensis
What is local tilting of land called?
What has it done?
Epeirogeny
Caused areas of the Mediterranean to be submerged
How does tectonic change affect sea level?
Orogensis when tectonic uplift occurs and produces fold mountains then makes land beneath rise. A 1% increase in area of ocean can lead to a 40m drip in sea level
How is thermal expansion contributing to sea level change?
We are in an interglacial period so the earth is heating up causing global expansion
What is a landform of submergence?
Landforms created by eustatic rise and isostatic fall
What are landforms of emergence?
Landforms created by eustatic fall and isostatic rise
What are Rias?
Deepest at the mouth
Right angled to the coast
V shaped
How are Rias produced?
Former river valley drowned by rising sea level
Submergence
What are Fjords?
Steep valley sides
U shaped valley cross section
Straight and narrow
How are Fjords produced?
Former glacial valley drowned by rising sea levels
Submergence
What is seen at a Dalmatian coast?
Runs parallel to the coast
How are Dalmatian coasts produced?
Land runs parallel to the coast becomes flooded
Submergence
What is seen at a raised beach?
Cliff behind has erosional evidence
Vegetated
How are raised beaches formed?
Former wave cut platforms
Emergence
What is seen at a marine platform?
Gently sloped gradient
Former wave-cut platform
How are marine platforms created?
Gently sloping submerged land becomes exposed
What is the most likely reason for global warming?
Greenhouse gases emitted by humans from combustion of fossil fuels in cars, factories & electricity production, mainly CO2
Deforestation
Industrial revolution
Why are sea level rise predictions uncertain?
Not certain how much fuel we will burn in future
Sea levels done stay exact same
Temperatures vary
Countries may try and mitigate
Isostatic and eustatic balance
Shortage of resources
What are the impacts of sea level change?
Melting ice caps
Wetland flooding
Thermal expansion
Coastal plants affected
Flooding
Habitats destroyed
Soil contamination
Erosion increase
who predicts sea level change
The IPCC (intergovernmental panel on climate change)
Show change over the last 300 years
What happened in sea levels between 1901- 1990?
Increase of 1.5mm per year
What happened in sea levels between 1993- 2010?
Increase of 3.2mm per year
What are the IPCC predictions?
Low- 0.5 m
Intermediate- 1m
High- 2m
How much are sea levels rising by per year now?
4mm
