Coasts Flashcards
What is a coast?
where the land meets the sea.
What are high and low water marks the result of?
high and low tides.
What is the area between the high and low water marks called?
the shore.
What are waves a result of?
friction between the wind and the surface of the sea.
What three things affect the size of a wave?
wind speed
length of time wind blows in same direction
lenth of sea where wind blows (fetch of wave)
What is the top of a wave called?
a wave crest.
What is the bottom of a wave called?
a wave trough.
What is swash?
the wave that rushes onto a beach.
What is backswash?
wave that goes back into the sea after rushing on to a beach.
What are four features of destructive waves?
weak swash
strong backswash
high/steep
remove material from beach
What are four features of constructive waves?
strong swash
weak backswash
builds up the beach
low waves
What is longshore drift?
movement of sediment along a beach.
What are groynes?
barriers that trap sediment and reduce longshore drift.
What are cliffs and wave-cut platforms?
vertical or steeply sloping rocks
Where is a wave cut notch on cliffs and wave-cut platforms?
high tide level
How is a wave-cut platform formed?
the retreat of a cliff.
What are three features of headlands?
- projects out into the sea
- is usually longer than its breadth
- has sides which form cliffs
What are four features of bays?
- an approximately semi-circular shape of sea extending into the sea
- a wide open entrance from the sea
- land behind it that is lower than the headlands on either side
- form on discordant coasts
What are discordant coasts?
coasts that have different types of rocks at 90 degrees to the sea.
Where do arches and stacks form?
discordant coasts.
How are arches, caves, and stacks formed?
wave refraction.
What are beaches composed of?
sand, shingle, or both.
How is material on a beach sorted?
fineness.
How are spits formed?
- prevailing wind
- longshore drift
- deposition builds up/repeated
- onshore winds
What is a spit called if it totally blocks a bay?
a bar.
What is the water behind a bar called?
a lagoon.
What forms in the waters behind a spit?
a saltwater marsh.
What do salt marshes become in tropical sheltered waters?
mangrove swamp forests.
How do salt marshes and mangrove swamps provide protection for the coast?
- preventing erosion
- allow a space for deposition to take place
- giving the water a gentle place to settle
How do salt marshes and mangrove swamps provide protection for the land?
- protects against hurricanes/floods
How do salt marshes and mangrove swamps provide protection for the sea?
- filters chemicals
- mud can collect there
How do salt marshes and mangrove swamps provide an important habitat?
- saltwater plants and mangroves can only grow there
- many birds + fish thrive in those conditions
How do salt marshes and mangrove swamps provide a recreational resource?
- fishing
- bird watching
- boating
What are stilt roots?
mangrove roots that anchor the plant in the soft mud and slow down water movement.
What are sand dunes?
ridges of sand which form at the bank of beaches and on spits.
How are sand dunes formed?
1) obstacle on beach
2) friction with obstacle slows onshore wind so sand is deposited around the obstacle
3) embreyo dunes form and join in a line called a fore dune
4) moves inland
5) dune becomes semi-fixed grey dune
6) dune becomes fixed dune
Where do lines of dunes form?
parallel to the sea.
What is marram grass?
grows on dunes
resistant to drought
network of long roots
slows wind and protects sand dunes from erosion
Why are semi-fixed dunes grey?
because of the humus from plant decay.
How can you tell which dunes are the oldest?
further inland = older
What does an increase in the depth of soil of a dune do?
more humus content
more water retention
What are the pHs of young and old dunes?
young dunes - alkaline
old dunes - acidic (rainwater leaches nutrients)
What are slacks?
long, marshy depressions that lie between dune ridges and contain water-loving plant species.
What is a blowout?
a depression in a sand dune caused by wind removing exposed sand.
Where are coral reefs found?
between latitudes 30* north and 30* south.
Where do coral reefs grow?
below low tide level.
What do coral reefs need to thrive?
oxygen, food, clear/clean water, high salinity, sunlight.
What are the three types of coral reefs?
Fringing reef - right around the isalnd
Barrier reef - slightly off the island coast
Atoll - in a circle not around an island
