All Coasts (3.11 still to add)

What are high energy environments?

Stretches of Atlantic facing coast, where waves are powerful for much of the year. The rate of erosion exceeds the rate of deposition.

What is a low-energy coastline?

Typically sandy and estuarine stretches of coast where the waves are less powerful or where it is sheltered from larger waves. The rate of deposition exceeds the rate of erosion.

What are the three main types of rock?

Igneous- formed from volcanic activity and includes basalt and granite.

Metamorphic- when the original rocks are put under a lot of heat and pressure that it causes them to transform into a different rock. Includes schist and quartzite.

Sedimentary- when sediment from animal bones or erosion is compacted over millions of years to form a rock. Includes chalk, clay, sands and sandstone.

What creates short term high energy coasts?

Storms and severe weather

What can you think of the coast as?

A system, as it is constantly changing and contains inputs, outputs and processes. Any change to a component can impact the rest of the system

What are the inputs into a coastal system?

Marine, atmospheric, land and people

What are the processes in a coastal system?

Weathering, mass movement, erosion, transport and deposition

What are the outputs in a coastal system?

Erosional and depositional landforms, and different types of coasts

What is the littoral zone?

A zone that stretches out into the sea and onto the shore. It is split into four sections: backshore, foreshore, nearshore and offshore.

Why does the littoral zone vary? (short and long term)

Short term factors, such as individual waves, daily tides and seasonal storms

Long term factors, such as changes to the sea levels or climate change

What are sediment cells?

Areas of water that consist of zones of erosion, transportation and deposition

Why are no coastline classification systems perfect?

High energy coasts can be mainly rocky, but also have long stretches of sand and estuaries. Low energy coasts are mainly long stretches of flatter coastline however there are still some high cliffs.

What is coastal morphology?

The shape and form of coastal landscapes and their features

What is coastal recession?

Another term for coastal erosion

What is lithology?

The physical characteristics for a particular rock

What are strata?

Layers of rock

What are bedding planes?

Natural breaks in the strata, caused by gaps in time during periods of rock formation

What are joints?

Fractures caused either by contractions as sediments dry out or by earth movements during uplift

What are folds?

Formed my pressure during tectonic activity, which causes rocks to buckle and crumple

What are faults?

Fractures caused when the stress or pressure a rock is exposed to exceeds its internal strength, which then move along fault planes

What is dip?

The angle at which rock strata lie

Horizontal strata

Produces wave cut platforms and notches

Dip gently towards the sea

Frequent jointing

Steep dip towards the sea

Common to have sloping cliffs

Rocks dip inland

Stable

Rocks dip inland but with well developed joints at right angles to bedding planes

Unstable

Which rocks are impermeable?

Igneous (crystalline and resistant)

Sedimentary (shale, which is finely grained and compacted

Metamorphic (marble and schist are very hard and resistant)

Which rocks are permeable?

Jointed sedimentary rocks, such as sandstone and limestone

Define porous and give an example of a rock with this quality

Rocks that have air spaces between the particles, for example chalk

Give an example of a quickly eroding coast

Holderness coast, glacial till, 1-10 metres per year

Give an example of a slowly eroding coast

Cornwall, granite, 1 mm per year

What are the other factors that determine the rate of recession?

Absence of a beach

Rising sea levels

Human activities, such as building coastal defences

What is a concordant coast?

Where bands of more and less resistant rock run parallel to the coast

What is a discordant coast?

When the bands of more and less resistant rock run perpendicular to the coast

What is isostatic change?

When land rises or falls relative to the sea, often in response to the melting or accumulation of glacial ice. Land can also rise and fall due to tectonic activity.

What is eustatic change?

When the sea level itself rises or falls, partly as a result of the growth and decay of ice sheets

What are submergent coastlines?

A type of concordant coastline that has been flooded due to rising sea levels, an example of this is Dalmation coasts

What are emergent coastlines?

Another type of concordant coastline formed when water level has fallen or land has risen due to tectonic activity

When do headlands and bays form?

When rocks of different strengths are exposed at the coast

How do headlands affect incoming waves?

Headlands force the incoming waves to refract or bend, which concentrates their energy and leads to more erosion. This produces high cliffs and eventual erosion into stacks and stumps.

How do bays affect incoming waves?

When waves enter a bay, their energy is dissipated and reduced. This leads to the deposition of sediment, forming a beach.

What happens when waves approach the coast?

1. The water becomes shallower and the circular orbit of the water particles changes to an elliptical shape

2. The wavelength and the velocity both decrease and the wave height increases, causing water to back up from behind

3. Force pushes the wave higher so that it becomes steeper before spilling and breaking onshore

4. The water rushes up the beach as swash, and flows back as backwash

What is the fetch?

The distance of open water over which the waves travel

Describe a constructive wave

They are low, surging waves with a long wavelength

Strong swash, weak backwash

Beach grows in size

Describe a destructive wave

High, plunging waves with a short wavelength

Weak swash, strong backwash

Beach loss

Explain how beaches change with the seasons

Beaches consist of loose material, so their morphology alters as waves change. Seasonal changes in wave type create summer and winter profiles or gradients. Destructive waves are more frequent in winter because of increased storms and cold weather, whereas in summer they are more constructive.

How are berms formed?

The swash of a constructive wave deposits larger material at the top of the beach. This builds up, and the backwash becomes weaker. It only has the energy to move smaller material, so beach material becomes shorter near the shoreline.

How are berms destroyed?

By plunging waves and high-energy swash, and the strong backwash transports sediment offshore (depositing it on offshore bars)

What is abrasion?

When large sediment is picked up by waves and hurled at the cliff foot, chipping away at the rock.

What is hydraulic action?

The joints and cracks in a cliff can be weakened by compressing and expanding air, trapped in the joints or between the breaking wave and the cliff. The shear force of the breaking wave can also hammer a rock surface.

What is corrosion?

When alkaline rocks such as chalk or limestone are dissolved by weak acids in seawater.

What is attrition?

The gradual wearing down of rock particles by impact and abrasion, which gradually reduces the size of the particles.

What is differential erosion?

The selective erosion of areas of weakness, due to lithology or wave type

Describe stacks and stumps

Isolated pillars of rock that lie just off the coast and are surrounded by water. Stumps are completely covered in water at high tide.

Describe shoreline platforms

flat rocky platforms that extend out from the coasts and surround stumps and stacks

What is a wave cut notch, and how is it made into a wave cut platform?

A notch is created by the high level of erosion at the base of the cliff due to waves breaking there. As it gets bigger, the rock above it becomes unstable and collapses, leaving a platform.

How is a blowhole formed from the cave?

If the overlying rock collapses in a cave, then the water is able to get through to the surface, especially during storm high tides

Describe the process of longshore drift

Swash carries material up the beach in the direction of the prevailing wind, and then backwash carries material directly down the beach under gravity. This is repeated until the water loses energy and deposits the sediment.

Describe the four main ways in which coastal sediment is transported

1. Traction— relatively large and heavy rocks are rolled along the seabed

2. Saltation- smaller and lighter rocks ‘bounce’ along the seabed

3. Suspension- when lighter sediment is carried in the water

4. Solution- when sediment is dissolved in the water

What is tidal range?

The relative difference between high and low tides

Describe how a spit is formed

They form on drift aligned beaches, and where sand and shingle is moving across the beach but the water flow suddenly changes direction. Sediment begins to build up across the estuary mouth, however will rarely extend across it because of the outflow of water. They curve on the end as wave refraction carries material round into the more sheltered wave behind the spit.

What makes a beach swash aligned?

Sediment moves up and down the beach with little transfer

What makes a beach drift aligned?

Sediment is transferred along the coast by longshore drift

How is an offshore bar formed?

Destructive waves erode sand from the beach with their strong backwash and deposit it offshore in bars

What is weathering?

The gradual breakdown of rocks that can be divided into mechanical, chemical or biological weathering. It helps to increase the rate of erosion of some coasts.

What are 3 types of mechanical weathering?

Freeze-thaw weathering

Salt-weathering

Wetting and drying

What is freeze-thaw weathering?

When water enters cracks or joints in rock, it expands by about 10%. This exerts pressure on the rock, which forces the crack to widen. This happens repeatedly, and the rocks eventually break off to form scree, which are then picked up by the sea and used as tools in marine erosion.

What is salt-weathering?

When salt water enters cracks in rocks and then evaporates, it leaves salt crystals behind. These grow over time and exert pressure on the rocks, causing it to break off.

What is wetting and drying weathering?

Rocks rich in clay expand when they get wet and contract as they dry. This can cause them to crack and break up.

What is biological weathering and how can it occur?

It is when the presence of living organisms causes rocks to break away. It can occur when thin plant roots grow in small cracks in a cliff face, which then widen as the plant roots grow thicker, breaking up the rock. Water running through decaying vegetation becomes acidic, which leads to increased chemical weathering. Birds and animals build nests and burrows into cliffs, and marine organisms, which can also secrete acids.

What is chemical weathering?

When chemical reactions break down rocks. Carbonation is a key example of this, as rainwater absorbs carbon dioxide to form a weak carbonic acid. This reacts with calcium carbonate in rocks such as limestone and chalk to form calcium bicarbonate, which is easily dissolved.

What is mass movement?

The movement of weathered material down slope, as a result of gravity.

What factors influence the type of mass movement that occurs?

• the angle of the slope or cliff

• the rock type and its structure

• the vegetation cover

• how wet the ground is

What is soil creep?

It is the slowest form of mass movement and is almost continuous. It is a very slow downhill movement of individual soil particles.

What is solifluction?

A process that occurs mainly in tundra areas, where the ground is frozen. When the top layer of soil thaws in the summer but the layers below remain frozen, the surface layer becomes saturated and flows over the frozen subsoil and rock. It averages between 5 cm and 1 metre per year.

What are earth flows and mudflows?

An increase in the amount of water can reduce friction, causing earth and mud to flow over underlying bedrock. A slide involves material that is intact, and in a flow the material becomes jumbled up.

What are rock falls?

They are most likely to occur when strong, jointed and steep rock faces are exposed to mechanical weathering. They occur on slopes over 40 degrees, and the material breaks off and builds up at the bottom of the cliff, forming scree or talus. Block falls are similar, but the falls are with a single piece.

What are rock/debris slides?

Rocks that are jointed, or have bedding planes roughly parallel to the slope or cliff surface, are susceptible to landslides. An increase in the amount of water can reduce friction, causing sliding, and in a rock or landslide, slabs of rock/blocks can slide over underlying rocks along a slide or slip plane.

What is slumping?

They occur in saturated conditions, and the difference between sliding and slumping is that there is rotational movement in slumping. They occur on moderate to steep slopes and are common where softer materials overlie more resistant or impermeable rock, such as limestone or granite. It causes rotational scars and creates a terraced cliff profile.

What is eustatic change?

When the sea level itself rises or falls

What is isostatic change?

When the land rises or falls relative to the sea.

Describe processes of eustatic change

It is global, and happens when ice sheets either melt or form, changing the volume of water in the oceans.

Describe processes of isostatic change

The enormous weight of ice sheets makes land sink during glacial periods (isostatic subsidence). After it has melted the land readjusts and rises (isostatic recovery)

How is land in the north and west of the UK undergoing isostatic change?

This land was covered by ice sheets during the last Ice Age, and is still rising as a result of isostatic recovery.

How is the land in the south and east of the UK affected by isostatic change?

It is sinking, as a result of isostatic recovery and of the weight of sediment brought by rivers.

How does past tectonic activity have an impact on coasts around the world?

The uplift of mountain ranges and coastal land at destructive and collision margins, and local tilting of the land.

What is an emergent coastline?

Land that has previously been submerged that has risen either due to a fall in sea level or uplift

What are emergent coastline landforms?

• Raised beaches— they have emerged due to fall in sea level or rise of land. E.g. Fife, Scotlant

• Fossil cliffs— a steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now above high tide level. E.g. Ayrshire, Scotland (see image)

What is a submergent coastline?

Land that sinks relative to the sea level. This is due to rising sea levels or sinking of the land, either due to isostatic recovery or the weight of sediment.

What are submergent coastline landforms?

• Rias— these are sheltered winding inlets with irregular shorelines, and form when valleys in a dissected upland area are flooded. E.g. Kingsbridge Estuary, England.

• Dalmatian coasts— the rivers flow almost parallel to the coast, rather than at right angles to it, which gives it the characteristic long and narrow islands. E.g. Dalmatian Coast, Croatia.

• Fjords— formed when deep glacial troughs are flooded by a rise in sea level. They are long and steep sided, with a U-shaped cross-section and hanging valleys. They are much deeper inland than they are at the coast. E.g. Milford Sound, New Zealand.

At what rate is Holderness coast disappearing every year?

2 metres per year. Since Roman times it has retreated by 4 km, and at least 29 villages have been lost to the sea.

What are the three main reasons why the coastline at Holderness is retreating so rapidly?

• geology

• fetch

• longshore drift and beach material

Describe the geology of the Holderness coast

• It mostly consists of boulder clay (aka glacial till), which is a mixture of material deposited after the last Ice Age. It is structurally weak with little resistance to erosion

• The more resistant chalk band surrounding the boulder clay has created Flamborough Head

Why is fetch not the main factor that influences the waves at Holderness coast?

Because it is only 500-800 km long, compared to that of 5000 km of those coming from the Atlantic Ocean.

What are the factors that influence the fetch of the waves that hit Holderness coast?

• Currents, which add to the wave energy in the North Sea

• Low pressure weather systems. The air weighs less, raising sea levels which produces higher tides than normal

• Small, mostly enclosed seas often generate huge waves, as they are unable to disperse their energy.

• Sea floor topography

Why are Holderness’ beaches such a huge problem?

Boulder clay produces clay particles, which are fine and easily transported out to sea by suspension. This means there are few beaches to offer friction to absorb wave energy.

How is longshore drift impacting coastal erosion at Holderness?

The tides flow southwards, so longshore drift carries material south, which leaves the cliffs at Holderness poorly protected against wave attack.

Why are sub aerial processes affecting Holderness so badly?

• Freeze-thaw weathering and wetting and drying of boiulder clay are the most common sub-aerial processes at Holderness.

• Slumping is the main form of mass movement at Holderness. The slumped material collects at the cliff base and is then removed by the sea, causing the cliff to retreat.

How are central government agencies and the local government key players on the Holderness coast?

They are jointly responsible for coastal management, however funding for both has been cut since 2010 in order to reduce council tax.

How are stakeholders in the local economy key players on the Holderness coast?

Local businesses, such as those in the agriculture and tourism industry, want greater spending on coastal protection. Insurance companies are increasingly refusing to insure vulnerable properties.