Geo Flashcards
ABRASION
the wearing away of the shoreline by sediment carried by waves
ATTRITION
erosion caused by the knocking together of two materials
DUNE
concentrations of mound like landforms composed of sand that has been blown off the beach by onshore wind
CONSTRUCTIVE WAVE
strong swash carrying material onto the beach
DESTRUCTIVE WAVE
strong backwash carrying material away from the beach
SWASH
movement of water up the beach away from the sea as a wave reaches the shore
BACKWASH
movement of water down the beach
FETCH
the distance of uninterrupted water surface over which the wind has blown to form waves
GROYNE
timber, sheet steel piles, rock or concrete posts and boards which run at right angles to trap sediment drifting along the shore
HARD ENGINEERING
structures developed to protect the foot of cliffs and prevent erosion e.g. sea walls
SOFT ENGINEERING
protecting the foot of cliffs to prevent erosion using more natural methods e.g. beach nourishment
SALTATION
sand bounces across the surface of the beach blown by wind
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STACK
a residual post of rocking resulting from the continued erosion of arches
SWELL
a circular motion caused by wind in the open sea which is non-moving
WAVE REFRACTION
as waves enter shallow water approaching the coast they are affected by friction
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FORESHORE (or INTERTIDAL ZONE)
the bit in between the highest tide and the lowest tide. This area is the most important in terms on landforms and landscapes
BACKSHORE
from highest tide to the cliff or dune. This area only gets wet during floods and storms, it is also not affected by the tides (SUPRATIDAL)
DIFFERENTIAL EROSION
variation in the rates of erosion
JOINT
vertical crack in a roc
FAULT
vertical crack in a rock caused by tectonic activity
PIONEER SPECIES
the first species to colonize a new area of land (in many cases this is grass holding a dune together)
PRIMARY DUNES
parallel to the beach
SECONDARY DUNES
perpendicular to the beach
CORIOLIS EFFECT
caused by the spinning of the Earth
SPRING TIDE
when the moon, Earth, and sun line up, it causes a really high tide and a really low tide, meaning there is a large tidal range
TIDAL RANGE
the distance between the highest and the lowest tide
NEAP TIDE
when the moon is perpendicular to the line of the sun, there is a lower high tide and a higher low tide, meaning it has a small tidal range. This is because there is no longer the gravitational pull from the moon and the sun, it is now just the moon.
OFFSHORE BAR
forms when material has been dragged back by destructive waves, it is also called the breaking point because it encourages the waves to break.
BERMS
ridges on a beach, formed by constructive waves pushing stuff up but not being able to pull it back down the beach
PERCOLATION
the process of liquid passing through a filter of some sort, in this case rocks
WAVE CUT NOTCH
the area where the cliff has been undercut
CAVITATION
imploding air bubbles when they hit the cliff, they slowly erode the cliff over time
SPIT
a long narrow piece of land that has one end joined to the mainland, while the other projects out into the sea
TOMBOLO
a spit that joins and island to the mainland
BAR
a spit that develops across a bay to join 2 headlands
GRAVITY SETTLING
the water has less energy, and so can no longer carry material and so deposits its material
EROSION
the breakdown of rock by some external force which then transports the material to a new location
WEATHERING
the in-situ breakdown of rock by different agents that does not involve any type of movement
MASS MOVEMENT
the downward slope of material under the influence of gravity
What are the conditions for constructive waves?
- Created in calm weather, less powerful than destructive waves
- They break on the shore and deposit material, building up beaches
- They have a swash that is stronger than backwash
- They have long wavelength and are low in height
What are the conditions for destructive waves?
- Created in storm conditions
- Created from big, strong waves when the wind is powerful and has been blowing for a long time
- They occur when wave energy is high and the wave has traveled over a long fetch
- They tend to erode the coast
- Stronger backwash than swash
- Short wavelength and are high and steep
What effects waves?
Size and Energy is influenced by
- How long the wind has been blowing (throughout the day)
- The strength of the wind
- How far the wave has traveled (fetch)
Hydraulic Action
- As the wave approaches a rock face, air can become trapped in joints and cracks of a cliff face.
- When a wave breaks off a cliff, air is trapped and compressed into a very small space
- As the wave retreats, the compressed air is suddenly released - a mini explosion occurs. Small bits of rock around the crack in the cliff face may shatter as a result of the mini-explosion
Abrasion
- Sea water carries bits of broken rock and sand —> as the wave crashes onto a rock platform. Sometimes, bits of broken rock fall from a cliff face onto the rock platform.
- The water moves these bits of rock forward and backward over the rock platform
- Over time, the movement of bits of rock and sand by the waves grind down rock platform surfaces.
Attrition
-Involves bigger pieces of rock becoming smaller.
- These bits of rock become smaller as the waves smash rocks and pebbles on the shore and into each other
Chemical Weathering
- Rocks containing minerals.
- These minerals sometimes react when sea water ‘hits’ or wets the rock to produce a weak acid that helps to erode the rock over time
How does long shore drift happen?
- Material that erodes on the coastline is transported along the coast by waves and currents before deposition elsewhere
- LSD occurs when waves approach a coastline at an angle and the swash brings the sediment up onto the coast at the same angle. Due to friction and the pull of gravity, the sediment is then brought seawards by the backwash at a right angle to the coast.
This zig zag motion is repeated.
3 hard engineering strategies
- Sea wall
- Groynes
- Rock armour
Two soft engineering strategies
- Beach Nourishment
- Beach vegetation
