Flashcards in 188.8.131.52 Systems and Processes Deck (62)
What is the key part of the coastal system
Why is the primary source of all energy the sun?
Because it heats the air, making low pressure areas
How is wave energy generated?
The air that is in high pressure areas (cold air) moves towards those of where low pressure (warm air) has risen. Thus creating win energy
How are currents created?
By the permanent or seasonal overeat of surface water in the seas and oceans due to its temperatures
Why is wind a vital input into the coastal system?
It is a primary source of energy for other processes
It is an important agent of erosie and transport
What are the features of wind as an input into the coastal system?
Long term prevailing wind direct
A vehicle of abrasion - carries material that wears away landscape features
What are the charcteristics of a wave?
Why do waves slow down in shallow water?
Because friction in the seabed increases
What effect does the slowing down of a wave have on its characteristics?
Increases height and steepness until the upper part plunges forward and the wave 'breaks' onto the shore
What are the features of constructive waves?
Low wave height
How are berms formed by constructive waves?
The weak backwash has insufficient force to pull sediment off the beach so material slowly but constantly is moved up the beach, forming the ridges
What are the characteristics of destructive waves?
High wave height
High frequency (10-14 a minute)
Why do destructive waves have a strong backwash?
Because as they approach a beach, the rapidly steepen and plunge downwards when they break, therefore there is little forward movement of water
Why are most beaches subject to an alternating cycle kf constructive and destructive waves?
Because constructive waves build up the beach, causing it to be steeper
But destructive waves are associated with steep beach profiles, then destruct and reduce the beach profile
The pattern repeats itself
Why is dynamic equilibrium often impossible in the negative feedback cycle of waves and beach formation?
Be ause other factors like wind strength and direction are not constant
Why is the topography of the coastline important to determine the effects of wave action?
Because wave refraction around a coastline that is not a regular shape affects the energy of waves at different places
Why do headlands recieve concentrated wave energy?
Because water at the headland is deeper than that at the beach
Waves in deeper water do not lose speed as rapidly
So wave height is very high
Erosion is concentrated on the headland
What are longshore currents/littoral drift?
When waves approach the shore at an angle and swash and backwash then transport material along the coast in the direction of the prevailing wind and waves
What are rip currents?
Strong currents moving AWAY from the shoreline
Why do rip currents develop?
When seawater is piled up along the coastline by incoming waves
What is upwelling?
The movement of cold water from deep in the ocean towards the surface
The more dense cold water replaces the warmer surface water and creates nutrient rich cold ocean currents
They form part of the global ocean cirgulation currents.
What is a tide?
The periodic rise and dall of the level of sea in response to the gravitational pull ftom the sun and the moon
Why does the moon have greater influence on tides?
Because it is much nearer than the sun
How is a high tode created?
When the moos pulls water towards it and there is a compensatory bulge on the other side of the earth
What is the tide like in areas of the rest of world between the two bulges?
At its lowest
What do high tides follow?
The moon as it orbits the Earth
When is tide-raising force at its strongest?
Twice in a lunar month, when the moon, sun and Eart are in a straight line
What is spring tide?
When tides bulge at their highest (sun, moon and earth are in a straight line)
What are neap tides?
When the moon and sun are perpendicular to each other in relation to the Earth
High and low tides are between 10-30% lower than the average