Chapter 10 - The Work Of The Sea Flashcards
Describe the term ‘destructive wave’.
Destructive waves cause erosion during stormy weather.
What is the ‘fetch’?
The length of sea over which the wind blows the waves.
What are prevailing winds?
Winds that blow regularly from one direction.
How does the sea erode?
He sea erodes by hydraulic action, attrition and abrasion.
What is hydraulic action.
Hydraulic action is erosion carried out by the force of the waves against the coast. Air is in cracks and compressed by incoming waves. As pressure is released, this can cause a mini-explosion which can weaken and shatter the rock.
What is abrasion?
Abrasion is when the sea uses its load of rocks and stones to erode the coast.
What is attrition?
Attrition is when the seas load is worn down as the pieces smash against each other so that the stones are smoothed and made smaller.
How are bays and headlands formed?
Bays and headlands: When the sea erodes a coastline with bands of hard and soft rock. Sea erodes soft rock faster then hard rock by hydraulic action and abrasion. Soft rock forms bays and hard rock forms headlands.
Describe the term ‘constructive wave’.
Constructive waves deposit more material then is taken away.
What is a bay?
A wide area of the coast where the land curves inward.
What is a headland?
A high piece of land that just out into the sea.
What is a sea cliff?
A vertical height of rock along the coast.
How are sea cliffs formed?
- The waves erode and undercut the base of the cliff using hydraulic action and abrasion.
- Wave-cut notch forms at the base, between high and low water marks, which undermines the rock above.
- Face of the cliff falls down.
- A wave-cut platform formed as cliff retreats.
e. g. Cliffs of Moher, Co. Clare
How does the sea transport?
Swash and Backwash, Longshore Drift
Explain slash and backwash.
Swash: Water running up the beach from an incoming wave. Transports sand and pebbles
Backwash: Water moves back down the beach
Swash stronger then Backwash: Constructive Waves (building beach)
Backwash stronger then Swash: Destructive Waves (removing beach)
Explain longshore drift.
Longshore Drift: When waves hit at an angle, transporting material in zigzag
- Swash runs up beach at and angle and deposits
- Material is brought back by backwash
- Swash moves material along beach making sand-spits, sandbars
How is longshore drift controlled?
Damage such as blocked harbours and sand less beaches are controlled by groynes, which trap sand as it’s being transported along the beach.
Name 5 features of sea deposition.
Beaches, sandspits, sandbars, lagoons, tombolos.
Describe a beach.
-Composed of sand and deposited materials
Storm Beach: Bigger stones and rock deposited at the back of the beach above high water during a storm.
Sandy Beach: Between high and low water mark.
Sand Dunes: Formed when sand is blown and is trapped by plants or stones
How does the sea help people?
- Tourism => Resorts and shops e.g. Tramore, Waterford
- Ports => Imports and exports, ferry services e.g. Dublin Port
- Fishing => Trawlers are services by ports e.g. Killybegs, Donegal
How do people harm the sea?
Pollution: Oil spills and untreated sewage endanger wildlife
How does the sea harm people?
- Flooding: Huge waves flood low-lying places e.g. Netherlands
- Erosion: Farmland and houses are worn away by the sea
