Waves

• Wave is a disturbance that transfers energy from place to place
• The crest is the highest point on a wave. The trough is the lowest point on a wave.
• The wavelength is the distance from one point on the wave to the next corresponding adjacent point. Wavelength is a measure of distance.
• The wave height is the measurement from the top of a crest to the base of a trough. 
• Wave


  A disturbance that transfers energy from place to place

  
• Medium

  The material through which a wave travels (can be gas, liquid, or solid)

  
• In coastal areas, the medium for waves is water, the ocean/sea

  
• Wave crest


  The highest point on a wave

  
• Wave trough

  The lowest point on a wave

  
• Wavelength


  The distance from one point on the wave to the next corresponding adjacent point
• Wave height


  The measurement from the top of a crest to the base of a trough

  
• How a wave breaks

  1. In open water, water moves in circular motion

  2. In shallow water, water moves in elliptical motion and front becomes steeper

  3. Water at front moves faster than rest of wave

  4. Front tumbles forward and wave breaks

  
• Constructive waves


  Help build a beach by transporting sediment to the shore (swash is stronger than backwash)

  
• Destructive waves

  Erode the shore by moving material back to the sea (backwash is stronger than swash)

  
• Characteristics of constructive waves

  • Small in height
  • Beach building
  • Gentle angle
  • Spilling breakers
  • Less energy
  • Strong swash and weak backwash
  • Low wave frequency

  
• Characteristics of destructive waves

  • Large in height
  • Beach eroding
  • Steep
  • Plunging breakers
  • Lots of energy
  • Weak swash and strong backwash
  • High wave frequency

  
• Ways waves use their energy

  • Erosion
  • Transportation
  • Deposition

  
• Erosion processes

  • Corrasion/Abrasion
  • Scouring
  • Hydraulic Action
  • Corrosion/Solution
  • Attrition
• Corrasion/Abrasion


  Rocks and pebbles flung by waves against cliff face, wearing it away

  
• Scouring


  Water hitting cliff face, impact acts as abrasive pad to erode cliff

  
• Hydraulic action


  Force of waves compressing air pockets in rocks/cliffs, air expands explosively breaking rocks apart
• Corrosion/Solution


  Chemical process that corrodes rocks on cliff face, usually limestone and chalk
• Attrition


  Sea grinds rocks together, making them smaller and more rounded
• Windward


  Side exposed to the wind or prevailing winds
• Leeward


  Side toward which the wind is blowing
• On many Caribbean islands, the leeward/western side is sheltered with low energy waves, while the windward/east coast is exposed to high energy Atlantic waves
• Coastal features from erosion

  • Headlands and Bays
  • Caves, Arches, Stacks and Stumps
  • Cliffs and Wave-cut platforms

  
• How headlands and bays form

  1. Discordant coastlines with soft and hard rock

  2. Soft rock erodes quicker, forming bays

  3. Hard rock erodes slower, forming headlands

  4. Headlands exposed to destructive waves, sheltering adjacent bays

  
• Wave refraction

  Waves approach coastline parallel to it, energy concentrated around headlands but reduced around bays

  
• How caves, arches, stacks and stumps form

  1. Sea erodes areas of weakness in headland

  2. Cracks develop into small caves

  3. Caves widen, forming arches

  4. Arch roof collapses, leaving stack

  5. Stack continues eroding, forming stump
• How cliffs and wave-cut platforms form

  1. Erosion greatest at cliff base, forming wave-cut notch

  2. Undercutting continues, cliff collapses and retreats

  3. Wave-cut platform left at base as cliff retreats

  
• Ways material is transported at the coast

  • Dissolved minerals carried in solution
  • Small fragments held in suspension
  • Large fragments transported by traction
  • Medium fragments transported by saltation
  • Longshore drift
• Longshore drift


  Zigzag movement of sediment along beach, caused by swash pushing material up at angle and backwash pulling it down perpendicularly

  
• Coastal deposition features

  • Beaches
  • Spits, Bars, Tombolos, Barrier Islands
  • Sand Dunes
  • Salt Marshes

  
• How beaches form

  Material from rivers, longshore drift, constructive waves, and cliff erosion builds up between high and low tide marks

  
• How spits form

  1. Longshore drift deposits material where coastline changes direction

  2. Spit grows outwards as more material is deposited

  3. Change in wind direction can cause hooked end (recurved lateral)

  4. Water trapped behind spit creates low energy zone for marsh development

  
• How bars form

  Similar to spits, but bar crosses bay, joining two headlands and creating a lagoon
• How tombolos form

  Spit continues growing to join land to offshore island
• What carries wave?

  A medium is a material in which a wave travels, a medium can be gas, liquid or solid. In coastal areas the medium is water