1.1.2 temporal variations and thei influence on coastal environments Flashcards
what is a tide?
the gravitational effect on water of the moon and the sun
what is a semi-diurnal tide?
a coast experiences two high tides and two low tides in 24 hours
what is a diurnal tide?
a coast experiences one high tide and one low tide in 24 hours
what is a spring tide?
where the sun and moon are aligned with eachother (twice a month)
what does a spring tide result in?
more gravitational pull on the tides, meaning more landform changes due to increased coastal erosion
what is a neap tide?
where the sun and moon are at 90 degrees to earth
what do neap tides result in?
less gravitational pull as it is in different directions meaning lower tides and less landform changes
what is the tidal range?
height difference between high & low tide
what is an amphidromic point?
where the tidal range/height is zero, this increases as you move away
what are the characteristics of a micro-tidal coast?
- small tidal range/height
- waves energy is concentrated area, meaning well-defined erosional features
what are the characteristics of a macro-tidal coast?
- large tidal range
- wave energy is dispersed over a large area, meaning more depositional features
what occurs at a coasts current?
- water rises, forming tidal current
- water floods inter-tidal zone, depositing material
- water falls (ebb tide), carrying material back to the subtidal zone
THIS IS EBB-FLOOD TIDAL
what is the inter-tidal zone?
areas where sea meets the land between high and low tide
what is the sub-tidal zone?
below the mean tide level, submerged
what are the characteristics of a rip current?
the water flows back to the sea at high speeds, common in longshore currents, river currents
how are waves formed?
-wave energy comes from the wind and the friction of it against the seawater surface, this creates motion in the upper layer of the water in any direction
-the circular motion gets disrupted by the seafloor as it gets deeper, therefore causing the wave to be elliptical (crescent-shaped)
what are the charactersitics of a constructive wave?
shorter, longer wavelength, gentle sloping, stronger swash
(6-8 waves per min)
what are the charactersitics of a destructive wave?
taller, shorter wavelength (more frequent), steeper, stronger backwash
(10-15 waves per min)
what are the current velocities like in a diurnal tide?
- current velocities are
relatively low at the start and end of each cycle and at their maximum in the middle of the rising or falling
tide.
