Coasts part 1- systems and processes Flashcards
closed system
Allows the input, transfer and output of energy but not matter.
open system
Allows the input and output of energy but not matter
example of closed system
domestic central heating
example of open
domestic water supply
inputs of a system
energy/ matter entering a system
outputs of a system
energy/ matter leaving a system
boundary of a system
edge of a particular system
store/ component
place where energy/ matter is stored/ held and matter can remain
flow/ transfer
movement of energy/ matter between systems
atmosphere
air that surrounds the earth made of gases and water vapour
lithosphere
the crust and uppermost mantle; constitutes the hard and rigid layers of the earth. This layer is split into tectonic plates
hydrosphere
discontinuous layer of water at or near the earth’s surface. It includes all liquid and frozen surface waters, groundwater held in soil and rock, and atmospheric water vapour.
biosphere
the total sum of living matter. The biological component of the earth’s systems.
negative feedback
system acts by lessening the effect of the original change and returning to equilibrium. (reversing effects)
positive feedback
change causes a further change and a snowball effect occurs. (effects are never undone)
tectonics influencing coastal landforms
movement of tectonic plates causes land to rise and fall; changing sea levels at coast and produce new coastal landforms. Sudden movements also cause tsunamis and flooding.
geology influencing coastal landforms
coastlines with harder rocks take longer to erode than coasts with harder rock; concordant and discordant coastlines create headlands and bays.
winds influencing coastal landforms
powerful winds in the direction of the coastline create constructive waves (leading to deposition) adn powerful winds away from coastline create destructive waves (leading to erosion).
vegetation influencing coastal landforms
coral reefs act as a buffer protecting coasts from erosion, preserving the coastline.
glaciation influencing coastal landforms
melting fresh waters from glaciers causes sea level rise as well as pushing heavier salt water downwards, changing ocean currents.
mass movement influencing coastal landforms
with rotational slumping, heavy rain is absorbed by unconsolidated material making up the cliff; the cliff becomes heavier and heavier eventually separating from the coastline and changing the coastline.
pollution influencing coastal landforms
an increased concentration of chemicals in the ocean by pollution, promotes the growth of algae which can damage the coastline and become fatal to wildlife.
temperatures influencing coastal landforms
frost erodes the coastline through freeze thaw weathering, creating landforms such as jagged edges and loose material falling from the coastline into the ocean.
UK prevailing winds
comes from the South West
wave formation
- water becomes shallower and circular orbit of water particles changes to an elliptical shape.
- wavelength and velocity both decrease, and the wave height increases
- this causes water to back up from behind and rise to a point where it starts to topple over and break.
fetch
distance of open water that the wind blows uninterrupted by land obstacles
wave refraction
depth of water increases rapidly off a headland; waves increase in height as their speed decreases. Erosion is then concentrated on the headland.
spring tide
The highest monthly tidal range, when the earth, sun and moon are in a straight line
neep tide
the lowest monthly tidal range, when the moon and sun are perpendicular to each other.
tidal range
vertical difference between high and low tides
surface ocean currents
typically wind driven
deep ocean currents
driven by wind, tides, coriolis force, the sun and water density differences
longshore currents
occur as most waves don’t hit the coast ‘head on’ but approach at an angle, generating a flow of water (which carries sediment) running parallel to the coastline.
rip currents
strong currents moving away from the shoreline that develop when sea water is piled up along the coastline by incoming waves. Initially the current may run parallel to the coast before falling out through breaker zone. They are very hazardous.
upwellings
movement of cold water from deep in the ocean towards the surface; the more dense cold water then replaces the warmer surface water and creates nutrient rich cold ocean currents.
high energy coasts
-high frequency destructive waves
-hydraulic action and erosion
-absence of a beach: erosion exceeds deposition
low energy coasts
-low frequency constructive waves
-gentle beach profile
-large beach and sand dunes: deposition exceeds erosion
sediment
naturally occurring material that has been broken down by processes of erosion and weathering.
sediment cells
areas along the coastline and the nearshore where the movement of material is largely contained; can be considered a closed coastal sub-system.
sediment budget
balance between changes in the volume of sediment being held within the system and the volume of sediment entering or leaving the system.
marine processes
operate on a coastlin and are connected to the sea: waves, tides and longshore drift.
sub-aerial processes
processes that slowly break down the coastline, , weaken underlying rocks and allow sudden movements or erosion to happen more easily.
frost shattering
water enters a crack, the water freezes and expands by roughly 10%, putting pressure on the rock and causing it to crack.
salt crystallisation
salt water evaporates from inside rocks, leaving crystals behind, these crystals grow over time eventually cracking the rock. Salt can also corrode the rock.
wetting and drying
rocks rich in clay expand when wet and contract when dry, causing them to crack and break up.
soil creep
particles rise towards the ground surface due to wetting/ freezing causing the particles to individually move down the hill in a zigzag motion; they’re too slow to be seen in operation.
mudflow
water gets trapped within rocks, increasing pore water pressure and forcing rock particles apart so the slope fails. Mud and earth then flow downhill over unconsolidated or weak bedrock.
rockfall
the sudden collapse or breaking away of individual rock fragments at a cliff face; occurring on steep/ vertical cliffs of heavily jointed and resistant rock.
landslide
a block of rock, that usually remains intact, moving rapidly downhill along a planar surface, often a bedding plane parallel to the ground.
landslip/ slump
a curved slide surface rather than flat, weak unconsolidated clays cause a build-up of pore-water pressure.
hydraulic action
wave attacks a cliff exerting tremendous hydraulic forcee, causing the compression of air within rocks eventually leading them to crack.
wave quarrying
removal of rocks and other debris on a cliff or wave-cut platform from their original position by wave action.
cavitation
when there’s intense erosion due to the surface collapse of air bubbles, in the implosion of the bubble a micro-jet of water is created that travels at high speeds causing great pressure on very small surface areas.
corrasion
sand and pebbles hurled violently at the foot of a cliff, chipping away at rock.
abrasion
sediment being dragged back and over a shoreline in the swash and backwash.
solution
weak acids in the water dissolve alkaline rock.
attrition
gradual wearing down of rock particles by impact and abrasion, making rocks smaller, smoother and more rounded.
Traction
Large stones and boulders are rolled and slid alone the seabed and beach by seawater- high energy environment.
Saltation
Small stones bouncing along the seabed- high energy environment.
Suspension
Very small particles of sand and silt carried along by moving water, can create a milky or murky appearance of the sea.
Solution
Dissolved materials transported within the mass of moving water.
Factors affecting the movement of seidment
- Wave energy: traction + saltation need a high energy environment
- Geology: If rocks dissolve in seawater there will be solution and suspension
- Estuaries: tend to have a lot of fine sediment that can be carried in suspension.
Swash
Movement of water up the beach as the wave breaks
Backwash
Movement of water down the beach after swash
Prevailing wind
Direction from which the wind most commonly blows
Sediment budget
balance between the inputs and outputs of a sediment cell
Formation of igneous rock
Either magma or lava cools and goes from liquid to solid, form crystals and gas bubbles can get stuck within
Examples of igneous rocks
-Basalt
-Granite
-Obsidian
Formation of sedimentary rocks
Broken pieces of sediment and squashed and compacted together
Examples of sedimentary rocks
-Sandstone
-Limestone
-Mudstone
Formation of metamorphic rocks
They have been changed over time; they get pushed down into the earth stretching and squashing causing them to change under extreme heat and pressure
Examples of metamorphic rocks
-Granite to gneiss
-Limestone to marble
-Shale to slate
Lithology
The characteristics of rocks
Resistance in terms of lithology
How well a rock can withstand erosion
Most resistant to least resistant rock types
Most- granite (Igneous)
Medium- limestone/chalk
Least- clay (sedimentary)
Permeability in terms of lithology
Whether a rock allows water to pass through
Permeable
Water is able to mov through
Porous
Water is able to bd stored in the rock
Physical makeup of rocks in terms of lithology
Whether the rocks have horizontal or vertical bedding planes
Chemical composition in terms of lithology
Whether the chemistry of the rocks makes it vulnerable to chemical decomposition e.g carbonate rocks are vulnerable to chemical weathering
