Coastal Landforms Flashcards
Cliffs form as the sea erodes the land. Over time cliffs ________ due to action of waves and ____________
Retreat
Weathering
Weathering and wave erosion cause a ______ to form at the _____ water _____. This eventually develops into a c_____.
Notch
High
Mark
Cave
Rock above the cave becomes ________ with nothing to support it and it c_______
Unstable
Collapses
Wave cut platforms are
Flat surfaces left behind when a cliff is eroded
The material eroded at the bottom of the cliff on a wave cut platform
Toe
Order of
Stumps Arches Caves Stacks Lines of weakness
Lines of weakness Caves Arches Stacks Stumps
Landforms found in cliffs are called
Cliff profile features
Stump formation
- Lines of weakness form due to weathering
- Weak areas in rock (eg joints) are eroded to form caves (chambers in headland)
- Depth of cave increases until equal to the width of headland = arch
- Arch widens and cannot support itself
- A stack (iscolated column of rock) remains which is exposed to erosion
- Stack is exposed to weathering and further erosion lead to it being a stump
Headlands and bays form when there are bands of…
Alternating hard and soft rock at right angles to the shoreline
Concordant coasts
Rocks on these coastlines run parallel park to the sea
The soft rock is eroded _______, forming a ____; compared to the harder rock which is eroded ________ forming a _________
Quickly
Bay
Slowly
Headland
Discordant coasts
Rocks on these coastlines run perpendicular to the sea
Wave cut platforms examples
Bullimah Bay, Australia
Glamorgan Bay, Wales
Arch examples
Legzira, Morocco
Azure Window, Malta (now collapsed)
Cave examples
Blue cave Zakythos, Greece
The Bay of Napoli, Italy
Stack examples
Sail Rock, Russia
Ko Tapu, Thailand
Stump examples
Proud Guiltar, UK
The Twelve Apostles, Australia
Cliff examples
Bonifacio, Corsica
Castellfollit de la Roca, Spain
Almost __% of the worlds coastlines are depositional in nature
20
Deposition occurs in environments that…
Are of low-energy
Where the effects of waves, tides and storms are reduced
Beaches form due to ________ waves which deposit ______ on the shore
Constructive
Sediment
Beach Gradient - shingle and sandy beaches?
Shingle - steep and narrow, larger sediment
Sand - wide and flat, finer sediment
What are runnels on the beach?
Grooves in the sand running parallel to the shore, formed by backwash draining to the sea
Berms are…
Ridges of sand and pebbles about 1-2m high found at high tide marks
Seasonal changes - summer vs winter?
Summer - calm conditions, constructive waves = material pushed up beach over wide area, berms
Winter - storm conditions, destructive waves = flatter beach due to erosional backwash
Cusps are …
Crescent-shaped indentations that form on beaches of mixed sand and shingle
Swash aligned beaches
Waves break parallel with the coast, so material is largely up and down the beach
Drift aligned beaches
Waves approach the coastline at an angle (LSD waves)
Spits
A spit is a long finger of land that protrudes from the mainland at the end of a drift aligned beach
Compound spits
Spits with more than 1 hook on their landward side, the hooks being formed due to a secondary most dominant wind which causes deposition.
Spit formation
- LSD transporting material along drift aligned beach
- Change in coastline direction, e.g. mouth of river
- Swash continues to transport at angle of prevailing wind - material deposited, partial extension
- River current and water depth - spit does not develop to mainland
- Compound spit - secondary wind direction
- Vegetation development behind spit, mudflats and salt marshes
Tombolos
Spits that connect the mainland to an offshore island via deposition
Japanese Tombolo
Angle Road of Shodo Island
Tombolo Formation
- LSD
- Change in coastline direction
- Material continues in swash direction until reaching the island
Offshore bars
Form when a spit joins 2 headlands together, across a bay or river mouth
A _______ forms behind the bar
Lagoon
Bars partly submerged by the sea are called
Offshore bars
Barrier Islands/Beaches
Long, narrow islands of sand that run parallel to the shore and are detached from it.
Barrier beaches tend to form in areas of…
A good supply of sediment
A gentle slope offshore
Fairly powerful waves
A small tidal range
Barrier island formation
NOT CLEAR
Scientists believe they formed after last ice age ended, ice melt caused rapid sea level rise.
Rising waters flooded the land behind beaches and transported sand offshore, where it was deposited in shallow water, forming islands. OR That the islands were originally bars, attached to the coast, which were eroded in sections - breaches in the bar.
Behind the barrier beach a _______ often forms
Lagoon or marsh
Sand dunes
Accumulations of sand blown into mounds by the wind (aeolian)
Sand dune formation
- LSD results in sand accumulating on beach
- Large inter tidal zone = dry sand
- At low tide, dry sand - onshore winds move sand up beach by saltation
- Barrier - driftwood, rocks
- Trapped sediment
- Colonisation of plants and grasses which stabilise the sand and trap more sediment - embryo dune
- Over time the dunes migrate inland as newer embryo dune form
Fluid threshold velocity
Higher velocity required for…
The velocity required to move the sand
Wetter sand
Dune require (4) to form:
Vast amount of sediment
Apple wind energy
Large tidal range
Flat land
Order of dunes
Embryo dune Foredune Yellow dune Grey dune Dune slack Mature dune
Hummus layer
Dead organisms / cause grey colour is
Saltmarshes
An area of coastal grassland that is regularly flooded by seawater
Mudflat
Created by the deposition of fine silts and clays in sheltered, low-energy coastal environments such as estuaries
