COASTAL LANDFORMS.pptx

lanforms which created by various coastal processes such as erosion, transportation and deposition.

1. COASTAL LANDFORMS PRESENTED BY: GROUP-C S HRITHIK SINGHA ROCKTIM GOGOI QUEEN CHETIA SONIA GHOSH KUKI MONJORI BORUAH

2. ACKNOWLEDGEMENT We would like to express our special thanks of gratitude to our professor Dr. Ratan Das who gave us this golden opportunity to do this wonderful presentation on “COASTAL LANDFORMS”. We came to know about so many new things and we are really thankful to it. Lastly but not the least we would like to thank all our group members for their valuable advice and contributions in completion of this presentation.

3. CONTENTS INTODUCTION COASTAL ENVIRONMENT WAVE TIDE CURRENT COASTAL PROCESSES DEGRADATIONAL PROCESSES AGGRADATIONAL PROCESSES EROSIONAL FEATURES DEPOSITIONAL FEATURES CONCLUSION REFERENCES

4. INTRODUCTION Coastal landforms, any of the relief features present along any coast, the result of a combination of processes, sediments and the geology of the coast itself. The coastal environment of the world is made up of a wide variety of landforms manifested in a spectrum of sizes and shapes ranging from gently sloping beaches to high cliffs .

5. What is Coastal environment? Coasts are the areas where the land masses meet the seas. This results in a special set of environments where the marine and terrestrial areas influence each other. There are mainly three processes active which modify the coast and the coastal environments: Waves Tides Currents

6. WAVES Waves are most commonly caused by wind. Waves move sand along the coast and onto beaches, where it is continuously recycled between surf zone sand bars and the beach dune system TIDES The alternate rising and falling of sea, due to the attraction of the moon and the sun is known as tides. Tide range dependent on relative position of earth, moon and sun. The Spring Tides- highest tidal range The Neap Tides – lowest tidal range

7. CURRENTS An ocean current is a continuous directed movement of sea water generated by wind coriolis effect, breaking waves, temperature and salinity differences. It has limited impact on coastal landscape. Some of the most important currents exists near the coast are: Wave-driven currents, Tidal currents, Wind-driven currents, and Bouyant plumes.

8. COASTAL PROCESSES Coastal landforms are fashioned by weathering, by sediment erosion and transport associated with wave action and tides, and by sediment deposition. It can be distinguished into two processes: Degradational processes Aggradational processes

9. . Degradation occurs mainly due to erosional activities of wind and water resulting in the transformation of a landform. Majorly two processes are prevalent namely : Shoreline weathering Wave erosion . Shoreline weathering Weathering processes act upon shore environments by the given ways : Chemical Weathering : Direct chemical attack by seawater takes place on limestone coasts: solution of carbonate rocks occurs. Salt weathering is an important process in shoreline weathering, being most effective where the coastal rocks are able to absorb seawater. 9 Mechanical Weathering : Water-layer weathering is associated with the wetting and drying cycles by waves and spray. As tides rise and fall, the zone between the low-water mark and the highest limit reached at high tide is wetted and dried periodically. Biological Activity : Direct action of organisms take place on the rock resulting in bioerosion. Tactics employed by organisms in the erosive process are chemical, mechanical, or a mixture of the two. DEGRADATIONAL PROCSSES

10. Wave erosion Wave and tidal activities make coastlines a dynamic entity as they regularly modify the coastal features . The pounding of the coast by waves is an enormously powerful process of erosion(constructive or destructive). Cliffs and other structures plunge straight into deep water, waves do not break before they strike and cause little erosion. Unconsolidated or loosely consolidated rocks(soft rocks) are the most susceptible to wave erosion. Strong turbulent waves also pick up debris and throw it against the shore, causing abrasion of shoreline structures. Tidal waves generated by the gravitational pull of the moon also contribute towards the erosion of the landforms in the coastal region . 10

11. Some of the important coastal landforms that are formed due to degradational process are given below : Cliff Headland Sea Cave Sea Arch Stack Stump

12. AGGRADATIONAL PROCESSES Aggradation means adding the sediments and raising the level of the land. Sediment transport Material eroded by the sea is moved along the beaches. Longshore drift Wave approaches beach at angle and sand moves in zigzag motion. The movement of sediment along the shoreline by longshore current. Longshore drift is maximal when waves strike the coast at around 30%. Beach drift It is the movement of sediment on the beach. Backwash swash moves sand down the beach. Groins and other structures used to interrupt drift and stabilize.

13. . . Sediment deposition Sand deposits form where amount of rock moving towards shore is greater than amount moving away . Very severe storm waves, storm surges and tsunamis may carry sediments from beyond the offshore zone. Sediment deposited on exposed continental shelves and then submerged by rising sea levels has been carried landward. Biological activity Some marine organisms build and some help to build particular coastal landform. A coral reef is an underground ecosystem characterized by reef building corals. The great barrier reef is world largest reef and cover about 2 million sq. km of tropical ocean. Salt - tolerant plants colonize salt marshes. Mangrove are a big component of coastal tropical vegetation.

14. Some of the important coastal landforms that are formed due to aggradational process are given below: Beach Berm Spits Tombolos Barrier islands Coastal sand dunes Marine deltas.

15. FACTORS AFFECTING EROSIONAL LANDFORMS Abrasion - waves transport material which hit the cliff and gradually wear it away. Hydraulic action - as waves approach the coast they trap air and force it into gaps in the cliff. Eventually this weakens the rock. Attrition - waves cause the rocks to crash against each other, breaking them down into smaller and rounder pieces. Corrosion (also known as solution) - salts and acids in seawater dissolve the rock gradually over thousands of years . In addition, changes in landforms can be a result of wind erosion, weathering and sub-aerial processes such as mass movement.

16. Erosional landforms The process of erosion can create different landforms along the coastline :- Headlands and bays Cliffs along the coastline do not erode at the same pace. When a stretch of coastline is formed from different types of rock, headlands and bays can form. Bands of soft rock such as clay and sand are weaker therefore they can be eroded quickly . This process forms bays. A bay is an inlet of the sea where the land curves inwards, usually with a beach. Hard rock such as chalk is more resistant to the processes of erosion. When the softer rock is eroded inwards, the hard rock sticks out into the sea, forming a headland. Erosional features such as wave-cut platforms and cliffs can be found on headlands, since they are more open to the waves. Bays are more sheltered with constructive waves which deposit sediment to form a beach

17. Cliffs and wave-cut platforms Cliffs are shaped through erosion and weathering. Soft rock erodes quickly and forms gentle sloping cliffs, whereas hard rock is more resistant and forms steep cliffs. A wave-cut platform is a wide gently-sloping surface found at the foot of a cliff . A WAVE-CUT PLATFORM IS FORMED WHEN THE FOLLOWING OCCURS : The sea attacks the base of the cliff between the high and low water mark. A wave-cut notch is formed by erosional processes such as abrasion and hydraulic action - this is a dent in the cliff usually at the level of high tide. As the notch increases in size, the cliff becomes unstable and collapses, leading to the retreat of the cliff face. The backwash carries away the eroded material, leaving a wave-cut platform. The process repeats and the cliff continues to retrea t.

18. Caves, arches, stacks and stumps Caves, arches, stacks and stumps are erosional features that are commonly found on a headland Cracks are widened in the headland through the erosional processes of hydraulic action and abrasion. As the waves continue to grind away at the crack , it begins to open up to form a cave. The cave becomes larger and eventually breaks through the headland to form an arch. The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea. This leaves a stack (an isolated column of rock). The stack is undercut at the base until it collapses to form a stump

19. COASTAL DEPOSITIONAL LANDFORMS BEACHES Sea beach is the area along shoreline, resulted from the wave actions, usually consists of well sorted sands, gravels, mud, pebble, shells of marine organisms, corals, algae etc. accumulated from the accretional activities of sea waves. Beach sediments are derived from wave and wind erosion of the headland, fluvial or estuarine sediments etc. Sand beaches are prevalent along tropical coast, probably because rivers carry predominantly fine sediments and cliff erosion donates little to littoral deposits in the tropics. Drainage channels, tributaries, stream etc. supplies immense quantities of sediments to the sea. However, sea water itself captures the sediments derived from the coastal erosional processes. Some of the important depositional landforms resulted from coastal activities are mentioned below: BERM It is an area occurs along the shoreline between sea and back beach, long narrow wedge of sand, gravels and beach sediments, steep slope facing the sea and gentle slope towards back beach. It is a depositional feature, appears after storm surge.

20. SPITS It is an extended stretch of beach material that sticks out to sea and joined to the mainland at one end. Longshore drift moves material along a coastline. Where the coastline changes direction or the power of the waves reduced and the transported material is deposited. Longshore drift moves material along the coastline and gradually the spit grows and sometimes develop a hook at tip portion. A spit is an unstable landform. TOMBOLO It is a small gravels or sands mound or island connected with narrow seaward extension from coast or mainland. Tombolos are formed from the refraction of sea waves which causes longshore currents of opposite direction to converge in a zone where sediments are accumulated and creates a tombolo. Two or more tombolos connected in a series called as tombolo cluster.

21. COASTAL SAND DUNES Sand dunes are small ridges or hills of sand found at the top of a beach, above the reach of the waves. Onshore winds cause the formation of sand dunes at the back of a beach. They are made from sediment blown off a beach to accumulate in areas sheltered from the action of waves and currents. Foredune, the first dune formed behind the beach is a prominent feature resulting from the interaction of nearshore processes, wind, sediments and vegetation. BARRIER ISLANDS Barrier islands are a type of dune system that are exceptionally flat or lumpy areas of sand that form by wave and tidal action parallel to the mainland coast. They are also called barrier beaches, barrier bars and offshore bars. They are subject to change during storms and other actions but absorb energy and protect the coastline.

22. TIDAL FLATES, SALT MARSHES AND MANGALS Tidal flats are banks of mud or sand that are exposed at low tide. They are not actually flat but slope very gently towards the sea from the high-tide level to a little below the low-tide level. Salt marshes form when tidal flats are high enough to permit colonization by salt-tolerant terrestrial plants. They are widespread in temperate regions. Mangals are communities of mangroves-shrubs that colonize tidal flats in the tropics and occur in river, tide and wave dominated environments. They specifically favour tidal shorelines with low wave energy. MARINE DELTAS Marine deltas are formed by deposition where rivers run into sea. So long as the deposition surpasses the erosion rate, a delta will grow. Some deltas form along low energy coasts with low tidal ranges and weak waves. Others form in high energy coasts with large tidal ranges and powerful waves .

23. CONCLUSION Coastal landforms, any of the relief features present along any coast, the result of a combination of processes, sediments and the geology of the coast itself. The three processes mainly active which modify the coast and the coastal environments are waves, tides and currents. Coastal processes can be divided into two as degradational processes and aggradational processes. Some of the important coastal landforms that are formed due to degradational process are cliff, headland, sea cave, sea arch, stack and stump. Some of the important coastal landforms that are formed due to aggradational process are beach, berm, spits, tombolos, barrier islands, coastal sand dunes, marine deltas.

24. REFERENCES R.J. Huggett, 4 th edition; Fundamentals of Geomorphology. Michael A. Summerfield; Global Geomorphology https://www.britannica.com/science/coastal-landform https://www.eionet.europa.eu/gemet/en/concept/1517#:~:text=Definition,%2C%20nursery%2C%20and%20resting%20areas https://www.bbc.co.uk/bitesize/guides/z6jx382 https://www.bbc.co.uk/bitesize/guides/zyfd2p3/revision/1 https://www.internetgeography.net/topics/landforms-of-coastal-deposition/

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