How do beaches work

For example, finer sediment is found closer to the water. This is partially because the moving water constantly breaks down the particles located here. As the beach moves further inland, the particles along its surface grow in size. Along the outermost edge of the beach are typically large rocks that have been washed up during storms. Generally speaking, beaches and shorelines cover a narrow area of land and tend to slope downward toward the waterline.

Rocks or coral reefs located off the shore are worn down by moving waves. As these materials are worn down, they become small particles of sediment that are carried by the waves in a state of suspension. In the case of sediment from further inland, the particles are washed to the larger body of water, where they are swept up by the waves and into the same state of suspension.

These suspended particles cause the moving water to have increased erosive ability, resulting in greater amounts of eroded particles in the water.

In some cases, fish and other marine animals contribute to the speed of erosion. This is particularly true in beaches that are located near coral reefs. Many of these animals rely on algae growing on the coral as a major dietary supplement. As they eat away the algae, they inadvertently cause the coral to break off into small pieces. Some pieces may even work their way through the digestive tracts of these animals, resulting in even smaller particles that are washed up into the waves.

Erosion is typically thought to decrease the size of certain landforms, however, this is not always the case. In fact, erosion actually works to increase the size and width of some beaches.

This growth occurs as the waves deposit the aforementioned sediment onto the land. Additionally, beaches may experience growth in size near river deltas, where rivers carry eroded sediment to the ocean. This sediment is deposited along the beach before being carried off into the ocean. The type of wave that reaches the coastline also plays a part in the formation of beaches.

Constructive waves, which are those that allow the water to recede and the beach particles to stop moving between waves, result in compacted sediment. This firm beach surface prevents future erosion. Ripples form overlapping V's extending outward from each pebble. Dark coloured minerals are usually heavier than light coloured minerals. Water rushing up and down the beach face concentrate the heavy minerals between ripple crests.

To be the provider of geoscience data globally Navigation Main content Bottom links. What is geology? Rocks and minerals. Fossils and dinosaurs. Geology around the world. Earth processes. Get involved. Coastal Processes and Beaches. Drip Water Hydrology and Speleothems. Earth's Earliest Climate. El Nino's Grip on Climate. Large-Scale Ecology Introduction. Methane Hydrates and Contemporary Climate Change.

Modeling Sea Level Rise. Ocean Acidification. Rivers and Streams - Water and Sediment in Motion. Principles of Landscape Ecology.

Spatial Ecology and Conservation. Restoration Ecology. Energy Economics in Ecosystems. Earth's Ferrous Wheel. The Ecology of Fire. Citation: Short, A. Nature Education Knowledge 3 10 Waves, tide, and wind dominate coastal processes and landforms. Rivers deliver sediment to the coast, where it can be reworked to form deltas, beaches, dunes, and barrier islands.

Aa Aa Aa. Coastal Processes. The coastal zone is that part of the land surface influenced by marine processes. It extends from the landward limit of tides, waves, and wind blown coastal dunes, and seaward to the point at which waves interact significantly with the seabed.

The coastal zone is a dynamic part of the Earth's surface where both marine and atmospheric processes produce rocky coasts, as well as beaches and dunes, barriers and tidal inlets, and shape deltas. The atmospheric processes include temperature, precipitation, and winds, while the major marine processes are waves and tides, together with water temperature and salinity.

The coast also supports rich ecosystems, including salt marshes, mangroves, seagrass, and coral reefs. The diverse coastal ecology is favored by the shallow waters, abundant sunlight, terrestrial and marine nutrients, tidal and wave flushing, and a range of habitat types. Waves — generation and types. Figure 1. As wind velocity increases, the period or time between waves, and wave length, increases, and the amount of energy transferred to the waves increases exponentially. Figure 2.

The highest waves occur in the Southern Ocean and north Pacific and Atlantic where they are generated by strong sub-polar lows. Tides and tidal currents. Figure 3.

Tidal inlet at Merrimbula, Australia. Wind and currents. Winds blowing over the oceans are responsible for generating ocean waves. Nearer the coast they can generate local seas — they can move the ocean surface and generate locally wind driven currents which in places can result in upwelling and downwelling.

Finally, when blowing over the beach, they can transport sand inland to build coastal sand dunes. Fluvial-deltaic systems. Figure 4. The Gasgoyne River delta in Western Australia delivers large volumes of sand to the coast where it is deposited in river mouth shoals and slowly reworked longshore to supply downdrift spits, barriers, and dunes.

Sea level. Sea level determines the position of the shoreline. During the last glacial maxima ice age 18, years ago, sea level was m below present, and the continental shelves were exposed. It then rose, reaching present sea level around 6, years ago, after which it was relatively stable.

Now, with climate change, it is beginning to rise again, and may rise as much as 1 m over the next years, triggering shoreline retreat, inundation, and erosion. Beach Systems. What is a beach? Figure 5. An idealised cross-section of a wave-dominated beach system consisting of the swash zone which contains the subaerial or 'dry' beach runnel, berm, and beach face and is dominated by swash processes; the energetic surf zone bars and channels with its breaking waves and surf zone currents; and the nearshore zone extending out to wave base where waves shoal building a concave upward slope.

Figure 6. Figure 7. Beach sub-systems. Figure 8. View of Makapu Beach, Hawaii, showing waves shoaling and steepening as they travel across and interact with the nearshore zone, then breaking across the surf zone. Figure 9. Figure Wave runup on the steep beach face at Ke lli Beach, Hawaii. A steep reflective beach with well developed high tide beach cusps at Hammer Head, Western Australia. Beach types. Beaches can range from low energy systems, where small waves lap against the shore, to those with high waves breaking across several hundred meters of surf zone.

They can also be exposed to micro 8 m. A plot of breaker wave height versus sand size, together with wave period, that can be used to determine the approximate beach state for wave-dominated beaches. Well-developed intermediate beach containing transverse bars and rip channels along Lighthouse Beach, Australia. A steep reflective high tide beach face fronted by a m wide tide-modified low tide terrace crossed by shallow drainage channels at North Harbour Beach, Australia.

A narrow high tide beach fronted by 1 km wide inter-tidal sand flats, upper Spencer Gulf, South Australia. The beach at Pingok Island, north Alaska, shown a during summer, with floating ice against the shore; b during freeze-up, with snow and sea ice accumulating; and c the frozen winter beach and ocean.

Beaches and barriers. A coastal sand barrier consisting of a beach and vegetated dunes, backed by a lagoon, at Big Beach, Queensland, Australia.

A series of low barrier islands separated by tidal inlets, at Corner Inlet, Victoria, Australia. Share Cancel.