Ynyslas Longshore Drift EarthCache
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Ynyslas Longshore Drift
This Earthcache is to demonstrate the power of the sea and is best done at low tide, but with care can be done at all but the very high winter tides.
You will need to walk along the surf line from the listed coordinates for at least ½ mile to gather the required information.
Longshore Drift
Longshore drift consists of the transportation of sediments (clay, silt, sand and shingle) along a coast at an angle to the shoreline, which is known as Swash and is dependent on prevailing wind direction. The falling tide that drags it straight back down the beach is known as Backwash. This process occurs in the littoral zone, and in or close to the surf zone. The process is also known as longshore transport or littoral drift.
Longshore drift is influenced by numerous aspects of the coastal system, with processes that occur within the surf zone largely influencing the deposition and erosion of sediments. Longshore currents can generate oblique breaking waves which result in longshore transport. Longshore drift can generally be defined in terms of the systems within the surf zone. Sediment transported along the shore and surf zone is influenced by the swash (occurs in the direction of prevailing wind), which moves the pebble up the beach at the angle moves the pebble back down the beach due to the influence of gravity.
Long shore drift in action at Ynyslas 22nd March 2015 9:10am High tide (5.7M)
Longshore drift affects numerous sediment sizes as it works in slightly different ways depending on the sediment (e.g. the difference in long shore drift of sediments from a sandy beach to that of sediments from a shingle beach). Sand is largely affected by the oscillatory force of breaking waves, the motion of sediment due to the impact of breaking waves and bed shear from long shore current. Whereas because shingle beaches are much steeper than sandy ones, plunging breakers are more likely to form, causing the majority of long shore transport to occur in the swash zone, due to a lack of surf zone.
Longshore Drift is the name given to the effect of wave action that hits the shoreline at an angle and can move vast quantities of sand and shingle sideways along the coast, eventually stripping away beaches leaving the hinterland exposed to even faster erosion.
The Cache
To illustrate this process, make your way from the listed parking, via the boardwalk through the sand dunes to the above co-ordinates.
Look along the beach at the vast amount of shingle along the surf zone.
Now some straightforward questions to email to claim the cache:
(You are welcome to log the cache and email answers later.)
1. From which direction does Longshore Drift affect this stretch of coastline?
2. Give reasons why this should happen.
3. Walk in a northerly direction along the shingle to where it appears to end (This will vary with time) and take a measurement of distance from the cache listing or take a coordinate reading.
4. The shingle is made up of many rock types which include Ailsa Craig Microgranite, Conglomerates Granites, Flint, Gniess, Jasper, Limestone, Pyroclastics, Sandstone, Porphyry and minerals. What mineral are the white stones?
5. Optional: Post a photo
Thanks to forcesofnature for additional information.
Additional Hints
(No hints available.)