These pictures have all been taken along coastlines. Why do they all look so different?
Coastal margins and their physical characteristics - ie (why do they look like they do!?)
Physical characteristics IB syllabus wants you to: Examine the relationship between coastal processes (tides, wave action, littoral drift, wind action), lithology, subaerial processes and different coastal landforms. Identify the major landforms of beaches, dunes and cliffs along advancing and retreating coastlines.
What are coastal margins? Shoreline – the boundary of the land and the sea Coastal margin – the area between the coastal terrain and to the depth of the wave base. The size of these varies drastically worldwide, e.g. it could be 10s of meters wide on steep rocky coasts, yet 100s of kms where estuaries move sea water far inland or where there are wide shallow continental shelves. Coastal terrain – the area that extends inland as far as the sea water, salt spray and wind blown sand extends. Wave base – the depth to which the waves can move sediment on the sea bed.
IB Syllabus: Examine the relationship between coastal processes, lithology, subaerial processes and different coastal landforms Coastal processes – e.g. Tides, wave action, littoral drift and wind action Lithology – the characteristics of rocks that can be seen with little/no microscopy, such as as colour, texture, grain size, or composition. The three major types of rock are igneous, sedimentary and metamorphic. Subaerial processes – these are the processes that occur in the open air or on the surface, rather than underwater. The atmosphere plays a very important role in these processes
Coastal processes - waves Waves “created by the transfer of energy from the wind blowing over the surface of the sea” As wind increases so does wave size Waves from local winds and travelling short distances are know as SEA Waves from distant storms and travelling large distances are SWELL
The basics of waves.... Energy of the wave depends upon: 1.Wind velocity 2.Period of time during which the wind has blown 3.Length of fetch (maximum distance of open water over which the wind can blow)
Wave terminology Task: 1.Make a sketch of the above diagram 2.Annotate the sketch diagram with definitions of wave height, wave length, wave period, wave velocity and wave steepness – use p.246 of Planet Geography to help you.
Wave terminology Waves in shallow water affected by friction on sea bed. Causes decrease in velocity and shortening of wavelength. However, rate of energy transported by waves is the same in deep and shallow water (hence increase in height and steepness) When the wave becomes unstable it breaks, runs up shoreline as SWASH (the water that washes up on shore after an incoming wave has broken) and returns as BACKWASH (seaward current that results from the receding swash on the beach face) Trough Crest Wave length Wave height
Task Complete table using the next 2 slides: Constructive wave Destructive wave Wave height Wave steepness Wave length Wave period/frequency High/low energy Beach gradient Stronger swash/backwash
Waves Waves bend and change as they approach the coast.
Wave refraction As the wave approaches the base of the wave slows down due to friction. As this happens the wave bends to fit with the shape of coast. The erosion due to wave energy is concentrated on the headlands. Bedford central schools district
Waves approach It is very rare that waves approach our coastline at right angles, think about the shape of the coast and the direction of the prevailing wind.
Wave refraction and orthogonals The physical geography of headlands and bays
Shallow water Shallow water
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave
Shallow water Shallow water wave