Photograph - Photography - Photo Painting - Digital Fine Art
A delightful evening at Kalaloch beach in the Olympic National Park in Washington, gave way to families spending the evening on the summer beach as the sun sinks slowly in the west, offering fun silhouettes.
Beaches are the result of wave action by which waves or currents move sand or other loose sediments of which the beach is made as these particles are held in suspension. Alternatively, sand may be moved by saltation (a bouncing movement of large particles).Beach materials come from erosion of rocks offshore, as well as from headland erosion and slumping producing deposits of scree. Some of the whitest sand in the world, along Florida's Emerald Coast, comes from the erosion of quartz in the Appalachian Mountains.A coral reef offshore is a significant source of sand particles. Some species of fish that feed on algae attached to coral outcrops and rocks can create substantial quantities of sand particles over their lifetime as they nibble during feeding, digesting the organic matter, and discarding the rock and coral particles which pass through their digestive tracts.The composition of the beach depends upon the nature and quantity of sediments upstream of the beach, and the speed of flow and turbidity of water and wind.Sediments are moved by moving water and wind according to their particle size and state of compaction. Particles tend to settle and compact in still water. Once compacted, they are more resistant to erosion. Established vegetation (especially species with complex network root systems) will resist erosion by slowing the fluid flow at the surface layer.When affected by moving water or wind, particles that are eroded and held in suspension will increase the erosive power of the fluid that holds them by increasing the average density, viscosity and volume of the moving fluid.
The nature of sediments found on a beach tends to indicate the energy of the waves and wind in the locality. Coastlines facing very energetic wind and wave systems will tend to hold only large rocks as smaller particles will be held in suspension in the turbid water column and carried to calmer areas by longshore currents and tides. Coastlines that are protected from waves and winds will tend to allow finer sediments such as clays and mud to precipitate creating mud flats and mangrove forests.The shape of a beach depends on whether the waves are constructive or destructive, and whether the material is sand or shingle.Waves are constructive if the period between their wave crests is long enough for the breaking water to recede and the sediment to settle before the succeeding wave arrives and breaks. Fine sediment transported from lower down the beach profile will compact if the receding water percolates or soaks into the beach. Compacted sediment is more resistant to movement by turbulent water from succeeding waves.Conversely, waves are destructive if the period between the wave crests is short. Sediment that remains in suspension when the following wave crest arrives will not be able to settle and compact and will be more susceptible to erosion by longshore currents and receding tides.
October 26th, 2013
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