waves and currents

geological action of waves and currents, and the features that is morphological features forming as a result of its action is explained

1. WELCOME Presented by Haritha A Govt college kottayam

2. GEOLOGICAL ACTION OF WAVES AND CURRENTS COASTAL UPWELLING AND COASTAL DOWNWELLING

3. WAVES Generated by the wind blowing over the surface of ocean and sea water. Friction of wind moving over the water surface cause the water particle to move along circular or near circular orbits in a vertical plane parallel to the direction of wind. The ocean waves are oscillatory waves as they causes an oscillatory wave motion.

4. CREST TROUGH WAVE PERIOD WAVE LENGTH WAVE HEIGHT ZONE OF SURF SWASH BACKSWASH

5. CURRENT In the current the actual movement of the water over great distance , which may be caused by various factors such as, the difference in temperature , salinity, action of steady and periodic wind.

6. MARINE EROSION MARINE TRANSPORTATION MARINE DEPOSITION GEOLOGICAL ACTIONS OF WAVES AND CURENTS

7. MARINE EROSION HYDRAULIC ACTION ABRASSION ATTRITION CORROSION

8. FEATURES FORMED Blowholes Sea caves Sea arches Sea stack Sea stump Wave cut cliff Wave cut benches Wave cut notches

9. BLOW HOLES   A   blowhole  is formed as sea caves grow landwards and upwards into vertical shafts and expose themselves towards the surface, which can result in blasts of water from the top of the blowhole. Blowholes are likely to occur in areas where there are crevices, such as lava tubes, in rock along the coast .  These areas are often located along fault lines  and on islands .  As powerful waves hit the coast, water rushes into these crevices and bursts out in a high pressured release

10. WAVECUT PLATFORMS A wave-cut platform also called wave-cut benches  It is the narrow flat area found at the base of a sea cliff. This was formed by wave erosion as the waves undercut a cliff.   Sometimes the landward side of the platform is covered by sand, forming the beach, and then the platform can only be identified at low tides or when storms move the sand.

11. SEA CAVES Also known as a  littoral cave , is a type of cave formed primarily by the  wave action of the  sea. The primary process involved is erosion In order to form a sea cave, the host rock must first contain a weak zone . In metamorphic or igneous rock, this is typically either a fault and i n sedimentary rocks, this may be a bedding-plane parting or a contact between layers of different hardness

12. SEA ARCHES A sea arch is a natural opening eroded out of a cliff face by marine processes. Destructive waves erode along the line of weakness e.g . fault line or joint Repeated hydraulic action and abrasion widen and deepen the line of weakness . The supporting roof of the arch is known as the keystone

13. SEA STACK Sea stack  is consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by  wave erosion. They are formed when part of a headland is eroded by hydraulic action  Without the constant presence of water, stacks also form when a  natural arch collapses under gravity, due to sub-aerial processes like wind erosion

14. SEA STUMP

15. WAVECUT CLIFF   Also called an  abrasion coast . In coastal areas, the land surface dips at a relatively steep angle The continuous action of marine waves on the coastline, create a steep declivity known as a cliff

16. WAVECUT NOTCHES The process of cliff erosion . The sea attacks the base of the cliff forming a  wave - cut notch . The  notch increases in size causing the cliff to collapse.

17. MARINE TRANSPORTATION Transportation is the movement of material in the sea and along the coast by waves. The movement of material along the coast is called longshore drift.

18. Longshore drift happens when waves moves towards the coast at an angle. The swash (waves moving up the beach) carries material up and along the beach. The backwash carries material back down the beach at right angles. This is the result of gravity. This process slowly moves material along the beach. Longshore drift provides a link between erosion and deposition. Material in one place is eroded, transported then deposited elsewhere.

19. Longshore drift is the main process of transportation the material moves in four different ways. These are: Traction - large material is rolled along the sea floor. S altation - beach material is bounced along the sea floor. Suspension - beach material is suspended and carried by the waves. Solution - material is dissolved and carried by the water.

20. MARINE DEPOSITION Deposition is when eroded material is dropped by constructive waves. It happens because wave have less energy. Deposition creates a range of landforms Littoral deposits Neritic deposit Bathyal deposit Abyssal deposit

21. BARRIER ISLANDS SPIT BEACHES BARS TOMBOLO ISTHMUS Features formed:

22. BARRIER ISLANDS Barrier islands are long, narrow, offshore deposits of sand or sediment that run parallel to the coastline. They are separated from the main land by a shallow sound, bay, or lagoon

23. They usually occur in chains, consisting of anything from a few islands to more than a dozen The length and width of barriers and overall morphology of barrier coasts are related to parameters including tidal range, wave energy, sediment supply, sea-level trends, and basement controls

24. SAND SPIT A  sandpit  , a  deposition bar or beach landform found off coasts or lake shores . It develops in places where re-entrance occurs, such as at a cove's headlands, by the process of longshore drift by longshore currents.

25. The drift occurs due to waves meeting the beach at an oblique angle, moving sediment down the beach in a zigzag pattern. This is complemented by long shore currents, which further transport sediment through the water alongside the beach. These currents are caused by the same waves that cause the drift

26. A  beach  is a landform along a body of water. It usually consists of loose particles, which are often composed of rock, such as sand, gravel, shingle, pebbles, or cobblestones. The particles comprising a beach are occasionally biological in origin, such as mollusc shells or coralline algae. Sand Beaches Rock Beaches Lava Beaches BEACHES

27. A   shoal  is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body of water to near the surface. Shoals are also known as  sandbanks ,  sandbars , or  gravel bars . Two or more shoals that are either separated by shared troughs or interconnected by past and or present sedimentary and hydrographic processes are referred to as a  shoal complex SHOAL

28. TOMBOLO A deposition landform in which an island is attached to the mainland by a narrow piece of land such as a spit or bar. Once attached, the island is then known as a tied island. Several islands tied together by bars which rise above the water level are called a  tombolo cluster .  Two or more tombolos may form an enclosure (called a lagoon) that can eventually fill with sediment.

29. UPWELLING Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water . The three main drivers that work together to cause upwelling are wind,  Coriolis effects, and  Ekman transport Coastal upwelling is the best known type of upwelling, and the most closely related to human activities as it supports some of the most productive fisheries in the world.

30. COASTAL UPWELLING   Wind-driven currents are diverted to the right of the winds in the Northern Hemisphere and to the left in the Southern Hemisphere due to the  Coriolis effect . The result is a net movement of surface water at right angles to the direction of the wind, known as the Ekman transport When Ekman transport is occurring away from the coast, surface waters moving away are replaced by deeper, colder, and denser water .  Normally, this upwelling process occurs at a rate of about 5–10 meters per day, but the rate and proximity of upwelling to the coast can be changed due to the strength and distance of the wind Upwelling occurs in the open ocean and along coastlines.

31. Downwelling is the process of accumulation and sinking of higher density material beneath lower density material, such as cold or saline water beneath warmer or fresher water or cold air beneath warm air. It is the sinking limb of a convection cell.  Upwelling is the opposite process and together these two forces are responsible in the oceans for the  thermohaline circulation. The sinking of cold lithosphere at  subduction zones is another example of downwelling in plate tectonics. DOWNWELLING

32. COASTAL DOWNWELLING Downwelling occurs at anti-cyclonic places within the ocean where warm rings are spinning clockwise creating surface convergence. When these surface waters converge, they push the surface water downwards. Another way that downwelling can occur is by the wind driving the sea towards the coastline. Regions that have downwelling have low productivity because the nutrients in the water column are utilized but are not continuously resupplied by the cold, nutrient-rich water from below the surface.

33. Thank you