Parts of the Beach:
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Swash zone: is alternately covered and exposed by waves.
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Beach face: sloping section below berm that is exposed to the swash of the waves.
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Wrack line: the highest reach of the daily tide where organic and inorganic debris is deposited by wave action.
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Berm: The nearly horizontal portion that stays dry except during extremely high tides and storms. May have sand dunes.
What are Beach Cusps?
Beach cusps are shoreline formations made up of various grades of sediment in an arc pattern.
Parts of Beach Cusps:
The horns are made up of coarser material and the embayment contains finer sediment. They can be found all over the world and are most noticeable on shorelines with coarser sediment such as pebble beaches. However, they can occur with sediment of any size. They nearly always occur in a regular pattern with cusps of equal size and spacing appearing along stretches of the shoreline. These cusps are most often a few meters long. However, they may reach 60 m (200 ft) across. Although the origin of beach cusps has yet to be proven, once cusps have been created they are a self-sustaining formation. This is because when an oncoming wave hits the horn of a beach cusp, it is split and forced into two directions. The crashing of the wave into the cusps slows its velocity, causing coarser sediment to fall out of suspension and be deposited on the horns. The waves then flow along the embayments (picking up finer sediment) and run into one another in the middle. After this collision, these waves attempt to flow back out to sea where they are met by incoming waves. Therefore, once the cusp is established, coarser sediment is constantly being deposited on the horn and finer sediment is being eroded away from the embayments. Seen below is a diagram of a beach cusp.
Sand:
Sand is divided into five categories based on its size:
-Very fine sand (1/16 – 1/8mm)
-Fine sand (1/8 – 1/4mm)
-Medium sand (1/4mm – 1/2mm)
-Coarse sand (1/2mm – 1mm)
-Very coarse sand (1 mm – 2mm)
These are accurate measurements according to the Udden-Wentworth Scale
Logging Tasks:
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Did you observe any beach cusps at the GZ during your visit? If so, estimate the width of the average cusp.
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Examine the sand located at the “horn” of the cusp. What category does it fall under according to the Udden-Wentworth Scale?
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Examine the sand located at the “embayment” part of the cusp. What category of sand does this fall under?
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Compare your answers for 2 and 3. Where is the smallest type of sand located in the cusp? The largest?
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What types of debris did you find at the wrack line? Name specific examples that you observe.
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As of June 2019, earthcaches are now allowed to have a required photo logging task. Please provide a photo of yourself, your GPSr, or a personal item that proves that you have visited this site. Please post this in your log.
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**Geocachers that do not complete all of the necessary logging tasks above will result in a log deletion.
Sources:
https://en.wikipedia.org/wiki/Beach_cusps
http://worldlandforms.com/landforms/beach-cusps/
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