Victoria - Beach Formation
Tasks:
- How is a beach formed by natural processes and what factors influence the type of sediment that is deposited?
- Is this beach a reflective, dissipative or intermediate beach type? Explain what features and processes you have observed that indicate this type.
- How would you describe the size of the pebbles on this beach? What size are the grains and what could this size tell you about the origin of the material?
- Take a picture of yourself or a piece of paper with your name on site without completely giving spoilers. The photo is a mandatory task for your log.
Log this cache as “Found it” and send me the answers to the questions to “silka03.earthcache@gmail.com” or via Geocaching Message Center. Not in your log! You may then log immediately. I will get in touch with you.
Have fun!
Geological History of the area
The beach south of Victoria is unusual because it combines natural post-glacial sediments with a shoreline that is now bounded by concrete structures. Instead of being fed by eroding cliffs or rocky headlands, the sand and gravel here originated from glacial deposits that were reworked by waves and tides after the last ice age. Today the retaining walls frame the beach and limit its migration, but the gently sloping profile and the mix of well-sorted sediments still reveal the natural coastal processes that shaped it. This makes the site a rare example of how glacially derived beaches can persist even when confined by modern human-built boundaries.
Beaches are dynamic coastal areas consisting of loose sediment that has been transported along the coast by water currents. These sediments can range from fine sand to coarse gravel and are important elements in the geomorphology of coastal landscapes.
A beach not only protects the coastal region from erosion by waves, but also serves as a habitat for many animal and plant species. These sedimentary deposits, which consist of various materials, are the result of a complex interaction between waves, wind and tides.
Beaches make up about two-thirds of the coasts that are not covered by ice, and they can provide a protective buffer zone for adjacent coastal formations such as cliffs and dunes.
Formation and material: Beaches are formed by the deposition of sediments transported by rivers, waves and other geological processes. The origin of these materials can vary greatly, ranging from continental materials carried by rivers to biogenic sediments resulting from the decomposition of shells and other marine organisms.
There are three main types of sediments found in beaches:
- Terrigenous sediments: Materials derived from land, such as silicates and minerals.
- Biogenic sediments: Sediments that are formed in situ, i.e. directly on the beach, by marine organisms such as mussels and corals.
- Lithogenic sediments: Sediments formed by the decomposition of rocks.
The type of sediment largely determines the structure and appearance of a beach. Depending on the material, beaches can have different colors and textures.
Slope and shape of the beach: The shape of a beach is mainly influenced by the waves. There are two main profiles of a beach:
- The summer profile, which is characterized by a gentle slope and typically shows an accumulation of sediment.
- The winter profile, which is steeper and often shows greater erosion.
The profile of a beach can therefore vary greatly depending on the season.
Zoning of a beach: Beaches can be divided into different zones:
- Foreshore (front beach): The area between high and low tide.
- Berm: An almost horizontal area created by the deposition of sand by waves.
- Backshore: The area that is rarely reached by waves and where the first dunes often begin.
- Dunes: Sand deposits created by wind accumulation that serve as protective barriers against erosion.
Beach types: There are two main types of beaches:
- Reflecting beaches:these beaches have a steep slope and often consist of coarse sand. They are characterized by a narrow surf zone and less sediment deposition. These beaches reflect most of the wave energy and are often found in sheltered bays or behind rocks.
- Dissipative beaches:These beaches have a shallow slope and a wide surf zone. The waves break further away from the shore and lose energy as they move across the wide sandy area. These beaches are often safer for swimmers as the wave energy is spread over a larger area.
https://www.geokartieranleitung.de/Fachliche-Grundlagen/Genese-und-Geogenese/Geogenetische-Definition/Lockergesteine/entry/6fdb0d04-e2b0-4417-9b60-5d447781829b/mid/3427
https://www.sur-la-plage.com/articles/la-formation-des-plages-28.php
https://www.researchgate.net/figure/Cross-section-of-a-beach-with-terminology-used-in-the-Puget-Sound-area-modified-from_fig1_23517196
https://friendsofibsp.org/breaking-news/science-of-the-shore-a-tale-of-two-beaches-winter-summer-beach-profiles/