1.1.2:temporal variations influence on coastal environments Flashcards
Rapid processes
3
tides
waves
currents
Tides motion
Periodic rises and falls
High tide
When the earth’s surface is close to the moon it pulls on the water and causes it to rise = high tide
Low tide
When the earth’s surface is further from the moon, the impacts of this gravitational pull is less = low tide
Spring tide
Big tide
When the sun, moon and earth are all in a straight line = the tide raising force is the strongest
Neap tide
Twice a month, little tide, the moon and sun are positioned at 90 degrees to each other in relation to the earth
The Earth orbits the sun
365 days = one orbit
The moon orbits the earth
28 days
Diurnal
daily
semi-diurnal
2 high tides and 2 low tides a day approx.
every 24 hours
diurnal tides
1 high tide and 1 low tide a day
Tidal ranges
3
macro-tidal
meso-tidal
micro-tidal
Macro-tidal
more than 4m
Meso-tidal
2 to 4m
Micro-tidal
less than 2m
Destructive wave
weak swash, strong backwash
Constructive waves
strong swash, weak backwash
Factors affecting waves
3
beach gradient
fetch
wind
What forms waves
the wind
How does the wind form waves?
Frictional effect on seawater = motion on upper surface of water.
The waves break coz they reach the shallower part of the shore = waves change shape which produces different types of breaking wave
Types of currents
4
Tidal
Shore normal
Rip
Longshore
Tidal currents
Water floods the intertidal zone at high tide, moving and depositing sediment and then as the tide falls (ebb tide) sediment moves in the reverse direction.
Shore normal currents
Waves align parallel to the coastline, pushing water straight up the beach.
Rip currents
Water returning directly (after shore normal currents) away from the shore can form strong, fast-moving channels of water.
