Coasts

Define a sediment cell

A stretch of coastline, usually bordered by 2 prominent headlands, where the movement of sediment is more or less contained

Define a negative feedback loop

Changes are met with responses that restore the balance back to the original state

Define a positive feedback loop

One change from the original state that triggers continuous problems, and cannot restore itself

Define fetch

Distance the wind blows over the water

What direction is the prevailing wind in the Two Bay sediment cell?

South West (from Brazil)

Describe the management at Bournemouth Beach

100 groynes to protect against LSD, 15 million m(2) of beach replenishment.

What issues are being faced at Barton on Sea?

Management at Bmouth is starving it of sediment, no natural protection; Permeable cliff face susceptible to rotational cliff slumping

Define wave

Result of frictional drag between sea surface and the lowest wind layer, which is pushed into the sea by higher levels

Define swell

Steep waves formed by strong winds

Explain wave refraction

Change in wave orientation and frequency as they encounter a non-uniform coastline

Describe the characteristics of constructive waves

Long wavelength, strong swash, weak backwash, 6-10 per min, low energy

Describe the characteristics of destructive waves

Short wavelength, steep, very strong backwash, 11-15 per min, high energy

What do sand and shingle beaches each indicate?

Sand = strong swash, similar backwash, low percolation, low energy.

Shingle = strong backwash, high percolation, high energy

Explain how headlands cause wave refraction

Waves encounter shallower water in front of headland, increased friction, wave slows, higher frequency. Sediment moves towards bay, infrequent waves there

Define intertidal range

Shoreline between the highest and lowest spring tides where the most prominent wave activity takes place

Explain why spring tides occur

Gravity of moon & sun acting together, increased range, aligned at 180`

Explain why neap tides occur

Moon and sun at 90`, the gravities cancel eachother out and the tidal range is smaller

How are ocean currents created?

Surface current (10%) driven by wind and tides; wind pulls on it and drags lower water (deep-ocean = 90%)

Define gyres

Large, circular loops of moving water, driven by the coriolis effect (clockwise in northern hemisphere)

What is the coastal sediment budget?

The balance between sediment being added to and removed from the coastal system; dynamic equilibrium

What is the difference between erosion and weathering?

Weathering is the breakdown of rock in situ, whereas erosion involves its transportation

What is the slowest type of mass movement?

Soil creep - gradual movement of individual particles when either dislodged or pulled down by gravity

Define slumping

Rotational landslips where cliff collapses in different stages. Rapid movement

Name a type of very rapid mass movement + example

Rockfall, eg. Burton Bradstock, Dorset

Give 2 examples of chemical weathering + explanation

Hydrolysis: reacts with acidic water to create clay/acidic products

Oxidation: oxygen creates iron oxide in reaction, causes rusting and decomposition

Carbonation: dissolved CO2 reacts to form a solution

Hydration: water absorbed by minerals, forms crystals, rock crumbles due to pressure

Give 2 examples of physical weathering Freeze-thaw: water freezes, expands, melts and repeats to widen cracks in rock

Freeze-thaw: water freezes, expands, melts and repeats to widen cracks in rock

Surface unloading: rocks formed under pressure expand when exposed, sheets peel off

Salt crystallisation: water evaporates, leaves concentrate, crystallise and increase volume

Insolation weathering: rock constantly cools and heats due to poor conduction, expands and contracts, causes cracks

Define quarrying

Vibration of destructive waves dislodges boys of rock, undercuts the base of cliffs and erodes it.

Define discordant coastline

A coast where the different rock types are at right angles to the coast

Define concordant coastline

Alternating bands less/more resistant rock are parallel to the coast

Explain the role of geology in the formation of a cove

Concordant coastline, erosion exploits cracks in hard rock, less resistant rock behind erodes faster creative the cove itself, erosion slows when the hard band behind is reached, cove widens

Define wave cut platform

A narrow, flat area of rock, often at the base of a cliff, which is more visible at low tide

How are wave cut notches formed?

Wave energy attacks the base of the cliff, causing it to retreat as rock above falls

Explain the concept of a swash aligned beach

Sediment is moved up and down by low energy waves that arrive roughly parallel to the coastline (eg. St Ives)

Explain the concept of a drift aligned beach

Waves approach at an angle and cause LSD, which causes attrition and often forms a spit

Define a rip channel

A ripple in the sand on a beach that is formed by a strong backwash

Define a berm

A gently sloping, elevated ridge of sand in the back shore of a beach

What is a cusp?

Coarser material that absorbs wave swash

Why does sediment size increase as you move further up a beach?

Finer sediment is transported back by even a weak backwash whereas larger ones are deposited

How does a beach change in the summer?

A berm is formed, water level varies and the beach is steeper due to sediment being returned. Waves are constructive and low energy

Explain the formation of a spit

LSD moves sediment perpendicular to wave direction, dropped when currents create turbulence, curve created by short term changes

What is a compound spit?

A spit with multiple recurved ends, showing sequential growth

Define a barrier island

A series of detached islands parallel to the coast, formed by deposition off the shoreline that often form above high tide

Define a tombolo

A spit that connects an island to the mainland, created by LSD or deposition due to wave refraction

Define a psammosere

A plant succession initiated on sand

Name the 4 stages of sand dunes

Embryo/foredunes, yellow dunes, fixed dunes, woodland

Describe plant characteristics across sand dunes stages

Embryo = pioneer species (sandwort), salt-resistant

Yellow = salt intolerant, long roots (marram grass)

Fixed = variety, soil instead of sand, taller (heather)

Woodland = trees (oak, pine)

Explain how sand dunes are formed

Sand is deposited in excess, blown up by wind, trapped by debris, continues to collect until vegetation colonises, which continues, organic matter decays, soil forms, more vegetation, woodland eventually created

Explain the formation of salt marshes

Mud accumulates behind a spit; pioneer species colonise it, trap mud against roots; larger species add dead matter to grow the mudflat; no longer inundated, complex reefs grow; creeks develop, trapped sea water evaporates; trees grow

What separates a salt marsh and a mudflat?

Salt marshes have vegetation, mudflats don't

Define a salt marsh

A depositional tidal landform of silty sediment that forms in the upper tidal coastal zone, which is a halosere environment

Define a halosere

A plant succession that develops in salt water conditions

Describe past sea level conditions

They are thought to have reached 50m- < today < 200m+. Despite fluctuations, have been increasing on average since 150 mil. years ago

Define eustatic sea level change + examples

Change to the sea in relation to the land eg. thermal expansion, continental collision, sea floor spreading, melting of ice sheets

Define isostatic rebound

Land rebounding upwards due to lessened weight because ice sheets melted after the last ice age. Happening most in the north of the UK eg. Scotland

Give some reasons for isostatic sea level change

Tectonic uplift, isostatic rebound, storage of water as ice on land

Define submergent and emergent coastlines

Submergent = rising sea level/falling coastline

Emergent = falling sea level/ rising coastline

Explain how rias are formed

The floodplain of a river is permanently flooded as sea rises. Deep valleys are eroded which are then flooded again

What is a fjord?

Glacial valley drowned by rising sea levels, with steep sides and is U-Shaped. Tends to be fairly straight and narrow

Explain what a dalmation coast is

A series of island ridges parallel to coastline which are remnants of hills left as parallel river valleys flooded eg. Croatia

What are raised beaches?

Areas of former shore platforms that are left at a higher level than the present sea level

Who are the main stakeholders in UK coastal management?

DEFRA (Department of Environmental, Food, and Rural Affairs), The Environment Agency

What are shoreline management plans?

Documents describing and addressing the risks associated with coastal evolution. There are 22 SMPs in the UK.

Name the 4 options in the SMPs

Hold the line, advance the line, managed retreat, no active intervention

What is integrated coastal zone management?

An ICZM is a strategy designed to manage complete sections of the coast, introduced by the UN in 1992

Name some factors that might influence the protection given to coastlines

Tourism, World Heritage Sites, Marine protected areas, Sites of special scientific interest

Give 2 examples of soft engineering strategies

Beach nourishment, managed retreat, dune regeneration, beach re profiling, living shoreline