Geography Topic 4 - Coasts
THE COAST
Coastlines are usually densely populated, due to historical reasons such as fishing and trade
Much of Australia's population lives
by
the coast due to the milder
Climate
17/04/2024
DEFINITIONS Coast - The part
of the land adjoining
or near the sea.
Weathering The breakdown or
deterioration of rocks
Erosion- The wearing
away of rocks and
Earth's surface
COASTAL PROCESSES
BIOLOGICAL WEATHERING
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CHEMICAL WEATHERING
24/04/2024
WAVES AND EROSION
CONSTRUCTIVE WAVES -Low and wide
- Elliptical Movement
Biological weathering occurs When plants on the coastline. breakdown the rock.
PHYSICAL WEATHERING
Strong swash
Weak backwash - Flat
-Builds Structures
DESTRUCTIVE WAVES
8 per minute
-High
-Weak swash
-Circular Movement
01/05/2024
DEFINITIONS Fetch-the distance
of water over which
a wave travels
Swash-when a
wave breaks and travels up the beach Backwash-when a wave travels back to the Sea due to gravity.
REGOLITH
(SOFT ROCK)
SALT SOLUTION
HARD ROCK
RAINWATER WEATHERS SOFT ROCK
Chemical weathering occurs when sughtly acidic water touches rocks.
SALT LCRYSTALS FORM IN PORES
EXPANSION OF CRYSTALS
Physical weathering occurs when water gets into cracks. It evapourates and leaves salt behind. The crystals. grow over time and causes the rock
to break apart
Strong backwash
-Not flat
-Erodes beaches
minute
->15 per
EROSION
Abrasion - caused by large waves hurting things against a cliff
Attrition-caused by waves forcing rocies agains
each other
Solution-caused by salts and acids dissolving cli Hydraulic Action-caused by waves compressing air in cracks, which breaks rocks apart.
LANDFORMS OF COASTAL EROSION
HEADLANDS AND BAYS
HARD ROCK
SOFT ROCK
HARD ROCK
SOFT ROCK
09/05/2024
HARD ROCK
WAVE DIRECTION SOFT ROCK
HARD ROCK SOFT ROCK
Sub-senal
Ciff retreats infand
ng occurs
Caves, arches, stacks
onds or faults
and stumps formation.
6
Whan soft rock is eroded, but hard rock stays put, the soft rock forms bays and the bits of rook that stick out are called headlands.
CAVES ARCHES, STACKS AND STUMPS
A fault opens in the rock.
-Due to hydraulic action. the fault enlarges to form a notch. -Abrasion and hydraulic action widen the notch into a cave. Due to erosion, the cave opens and forms an arch. -The arch widens and the roof becomes to heavy and collapses. -This leads to a stack, which is standing, but being underout -The stack collapses, leaving a stump.
WAVE CUT PLATFORMS
Waves erode bits of rock at the bottom of cliff, it leaves a ledge. which collapses under its own weight, forming a wave-cut. platfonu.
Weathering weakn the coff
The
cats and
the detreats inland
The notch makes the diff unstable
and gravity collages it over time
Original
Over time the notch s enlarged by ation and hydraulic con
diff position
Erosion at the base of the c
at high de creates a notch
Wave Out
Wave out platform
formation
-Longshore drift is the transportation of material along the coast. -Waves hit the beach at an angle
1
-
·Swash carnes sediment up the beach at an angle. Backwash carries Sediment down the beach with gravity-perpendicular to the beach
-Constructive waves transport material to the beach.
BEACH
WIND DIRECTION
SPITS (LAND FORM CAUSED BY DEPOSITION)
-Spits are formed when coastlines change direction.
-When enough material from longshore drift is deposited, spits form.
MATERIALS
-Sediment is carried by longshore drift
-The coastline changes shape, and deposition occurs,
a long, thin ridge of material is deposited. This is the Spit
-A hooked end can form when the prevailing wind changes direction. Waves cannot get past a spit, therefore the water behind a spit is quite muddy.
-If wind changes direction, a spit will curve and leave a salt marsh behind
BAR
When a spit grows across a bay, and joins 2 headlands, a bar is formed. •Bars can enclose bays, resulting in lagoons behind them •Lagoons are shallow lakes trapped behind bars
TOMBOLO
- A tombolo is formed when a spit connects the Mainland coast to an island