Chapter 1 Coasts - Should Coastal Environments Matter

GATEWAY 1: How and why are coastal environments different and dynamic? What are coasts? ● Coast ​ is ​ area where land meets sea, covering land that is affected by waves and tides. ● Coast can be ​ cliffed, sandy, rocky, muddy ​ . Factors affecting coastal environments ● Waves ​ affect coastal environments - constructive waves and destructive waves. ● Tides ​ affect coastal environments by affecting processes like coastal erosion, sediment transport and deposition. ● Currents ​ like longshore current helps transport sediments, giving rise to a sandy coast. ● Geology ​ like hard resistant rocks leads to less erosion and less resistant rock leads to more erosion ● Human ​ activities create pollution and can affect a coast. ● Types of ecosystem ​ can cause differences. Mangrove systems or coral reefs can affect how a shore develops as they reduce the impact of waves on a coast. What are waves and how are they generated? Wave terminology ● Wave length ​ is the horizontal distance from crest to crest or trough to trough. ● Wave height ​ is the vertical distance between crest and trough. ● Wave frequency ​ is number of wave crests or troughs that pass through a fixed point. ● Wave steepness ​ is ratio of wave height to wavelength. ● Wave period ​ is time waves take to travel through one wavelength. ● Crest ​ is highest part of wave ● Trough ​ is lowest part of wave. Factors affecting wave energy ● Wind speed ​ because the faster winds blows, the greater the wave energy. ● Wind duration ​ because the longer the wind blows, the larger the waves are. ● Fetch ​ , which is the distance over which the wind has travelled over seas and oceans to form waves affects wave energy too because the greater the fetch the more energy waves have ● The higher the wave energy is, the steeper the wave and shorter it becomes. Waves in the open ocean or close to the coastline ● Waves in the open ocean have a long wavelength and low wave height, particles in the ocean also move in an orbit. ● Waves close the coastline, however, do not move in an orbit. ○ The water close to the coastline is shallow and waves start to interact with the seabed, changing shape. ○ As the waves continue travelling in shallow water, the base of the wave slows down due to friction. ○ This causes wave height to increase and wavelength to decrease. ○ Eventually this reaches a point where the base of the wave stops but the wave crest becomes steeper and topples over. ○ This causes the process of waves breaking onto the coast. How do waves affect coastal areas? Waves on the beach ● Swash ​ is formed when waves break and water rushes up a beach. Swash moves up the beach in direction of waves, carrying sediments with it. ● Backwash ​ is created when the swash loses energy due to gravity and friction to the sea and returns back to it, forming backwash. Backwash carries sediments from shore to the sea perpendicularly to the shoreline. Notes by some weirdo called Conrad Soon.. I don’t guarantee the full accuracy of the information here. Special thanks to Mrs Wong, the most wholesome and pure Geography ahma.

Types of waves Type of wave Constructive waves Destructive waves Places where they occur ● Low gradient, low energy environment. ● Occur on gentle coastal slope and sheltered coast. ● Steep gradient, high energy environment. ● Occur on steep coastal slope and open coast. Shape of wave ● Small, low waves ● Low wave height, long wavelength ● Large, high waves ● High wave height, short wavelength Frequency of waves ● Occur 6-8 per minute ● Occur 10-14 per minute Prominence of swash or backwash ● Swash more powerful than backwash ● Deposition process more prominent ● Accumulation of sediments results in creation of sandy coasts. ● Backwash more powerful than swash ● Erosion process more prominent ● Transport rocks and material away and erode coasts. Type of coast formed ● Form gentle, sandy slopes. ● Form steeper, coarser slopes. Wave refraction ● Wave refraction ​ is the process in which waves change direction as they approach a coast ● Waves tend to ​ converge on headlands ​ , leading to a higher concentration of wave energy which means larger waves which are usually destructive, leading to enhanced erosion. ● Waves tend to ​ diverge in bays ​ . The dissipation of wave energy leads to smaller waves which are usually constructive, leading to less erosion and more deposition. ● When they approach a straight coast at angle, they break parallel to coast. Why do coastal landforms and features vary from place to place? Coastal erosion (CASH) ● Corrasion ​ , where the impact of the sediments carried by the waves grinds against the rocks, weakening them and breaking them down. ● Attrition ​ , where the sediments in the wave hit and rub against one another, breaking into smaller pieces and becoming rounder and smoother. ● Solution ​ , where chemicals contained within sea-water may dissolve some rocks found on coast (e:g; carbonic acid against limestone) ● Hydraulic action ​ , where the impact of waves against the coast compresses air in between the rock’s joints and cracks and then releases it. This repeated action causes the joints to weaken and the rocks to shatter. Sediment transport ● Beach drift ​ and l ​ ongshore current ​ are the results of waves approaching coasts at angle, together they form ​ longshore drift. ● When waves approaching coast break at an angle to beach the beach, sediment move up beach at angle as swash and perpendicularly down as backwash. ● The resulting zigzag movement is ​ beach drift. ● When wave approach coast at angle, they create ​ longshore current in ​ nearshore zone ​ and move sediment along shore. ​ Longshore currents ​ are ocean currents that flow parallel to coast. ● The combined effect is known as ​ longshore drift ​ . Notes by some weirdo called Conrad Soon.. I don’t guarantee the full accuracy of the information here. Special thanks to Mrs Wong, the most wholesome and pure Geography ahma.

Sediment deposition ● Sediment deposition ​ typically occurs in areas where which have these characteristics. ○ Sheltered from strong winds. ○ Uncommon destructive waves. ○ Calm waters like those of mangrove coasts. ○ Deep bays sheltered by headlands ○ Common constructive waves ○ Shallow offshore water (allows sediments to rise above sea level quickly) ○ Light winds which will result in lower wave energy hence more deposition, ○ Prevalence of material that can be transported away as this will result in more deposition. In what ways do coastal landforms and features vary from place to place? Formation of cliff and shore platforms ● A ​ cliff ​ is a near-vertical and steep rock face found along coasts. ● Hydraulic action and abrasion may erode a crack or joint on rock surface, gradually enlarging crack or joint to form notch. ● Notch may be further deepened to produce bigger hollow space called cave. ● As process of erosion continues, overhanging cliff is formed, eventually collapse and materials deposit at foot of cliff. ● Some material may be carry by waves and throw against base of cliff, cause further erosion. ● Over time cliff retreat inland and gently sloping platform appears at base of where cliff used to be. ● Platform is called ​ shore platform ​ , which is submerged during high tide. ○ When drawing diagram, label shore platform, roof of cave, cave, cliff. Formation of headlands and bays ● Some coastlines have alternating bands of more resistant and less resistant rock. ○ Give example, e:g granite vs chalk ● Less resistant rocks will be eroded faster than more resistant rocks. ● Less