Great Place for a Spit Braai
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
This cache is on Woodbridge island. Although this isn’t really an island but a “SPIT”. Note: In order to answer the questions, it is suggested you start your journey in Blouberg and drive along the beach road to the cache site (from S33 49.805 E18 29.068)
A spit is a deposition landform found along coasts. At one end, spits connect to land, while at the far end they exist in open water. A spit is a type of bar or beach that develops where a re-entrant occurs, such as at cove's headlands, by the process of longshore drift. Longshore drift (also called littoral drift) occurs due to waves meeting the beach at an oblique angle, and backwashing perpendicular to the shore, moving sediment down the beach in a zigzag pattern. Longshore drifting is complemented by longshore currents, which transport sediment through the water alongside the beach. These currents are set in motion by the same oblique angle of entering waves that causes littoral drift and transport sediment in a similar process.
However, where the direction of the shore inland reenters, or changes direction, such as at a headland, the longshore current spreads out or dissipates. No longer able to carry the full load, much of the sediment is dropped. This is also known as deposition. This submerged bar of sediment allows littoral drift to continue to transport in the direction the waves are breaking, forming an above-water spit. Without the complementary process of littoral drift, the bar would not build above the surface of the waves becoming a spit and would instead be levelled off underwater.
Spits occur when longshore drift reaches a section of headland where the turn is greater than 30 degrees. In this particular case, the headland is Table Bay area – and the current having to turn around and between Robben Island. They will continue out into the sea until water pressure (such as from a river) becomes too much to allow the sand to deposit. The spit may then be grown upon and become stable and often fertile. A spit may be considered a specialized form of a shoal. As spits grow, the water behind them is sheltered from wind and waves, and a salt marsh is likely to develop.
Wave refraction can occur at the end of a spit, carrying sediment around the end to form a hook or recurved spit. Wave refraction in multiple directions will cause a complex spit to form. Incoming waves that come in a direction other than obliquely along the spit will halt the growth of the spit, shorten it or eventually destroy it entirely.
The sediments that make up spits come from a variety of sources including rivers and eroding bluffs, and changes there can have a large impact on spits and other coastal landforms. Activities such as logging and farming upstream can increase the sediment load of rivers, which may hurt the intertidal environments around spits by smothering delicate habitat. Roads or bulkheads built along bluffs can drastically reduce the volume of sediment eroded, so that not enough material is being pushed along to maintain a given spit.
If the supply of sediment is interrupted the sand at the neck (landward side) of the spit may be moved towards the head, eventually creating an island. If the supply isn't interrupted, and the spit isn't breached by the sea (or, if across an estuary, the river) the spit may become a bar, with both ends joined to land, and form a lagoon behind the bar. If an island lies offshore near where the coast changes direction, and the spit continues to grow until it connects the island to the mainland, it is then called a tombolo or a bar.
When talking about spits, the end of the spit attached to the mainland is called the proximal end and the end jutting out into the stretch of water, is called the distal end.
(Acknowledgement to Wikipedia.com).
In order to qualify to log this cache, you need to answer the following questions and email the cache owner. Any logs not accompanied by an email will be deleted.
1) Take a photo of you and your GPSr at this spot with any nearby lighthouse visible and include in your log. [Optional]
2) Comment on the landforms and especially the deposits of sand, and the nearby river/dam (Rietvlei) system that you observed from the initial waypoint to the cache site.
3) In the absence of human development and construction (e.g. coastal road and housing developments), where do you think the river mouth would be after a large flood?
4) Look along the beach – observe any evidence of sand being deposited against obstructions (pipes into water / jetties / large rocky outcrops. Which side id the sand piled higher (north or south)? Why do you think this is?
Additional Hints
(Decrypt)
Erzrzore gb fraq lbhe rznvy!