Geography 1 Flashcards
How do waves form?
Waves are formed by the wind blowing over the sea. Friction with the surface of the water causes ripples to form and these develop into waves.
What is the fetch?
The distance the wind blows across the water is called the fetch
Swash
Swash: Movement of water UP the beach
Backwash
Backwash: Movement of water back DOWN the beach
Constructive waves properties
SWASH is stronger than BACKWASH so waves run gently up the beach- material is carried onto the beach and deposited there.
Destructive waves properties
BACKWASH is stronger than SWASH, so waves crash onto the beach- material is eroded from the coastline.
Erosion
Erosion is the wearing away and removal of rock by forceful water wind and ice which then transport the material away.
Attritio\
Materials carried by the waves bump into each other and so are smoothed and broken down into smaller particles.
Hydraulic Action
The force of the waves enter cracks in the cliff and squash air into the crack. When the wave retreats, the air in the crack expands quickly, causing a minor explosion.
Solution
The acids in the salt water slowly dissolve rocks on the coast.
Abrasion
Waves throw material they are carrying against the cliff, sometimes at high velocity.
Suspension
Fine material such as clay and sediment is carried by the sea.
Solution
Dissolved minerals are carried by the sea
Traction
Large boulders and pebbles are rolled along the sea bed.
Saltation
small stones, pebble and slit bounces along the sea bed.
How is a wave cut platform formed?
The waves crash into the cliff base causing it to erode. The hydraulic action of the waves creates a notch to be cut into the cliff base. Air becomes trapped in cracks and joints on a cliff face. When the wave breaks the air becomes compressed, weakening the cliff and causing erosion. Gravity causes the eroded cliff to fall. The waves and abrasion causes the rocks from the fallen cliff to break up over time. The process begins again, with waves undercutting the next section of the cliff.
What is a discordant coast?
This means that the rocks are layered in discord, meaning that the rocks used can alternate from hard rock and soft rock.
How are headlands and bays formed?
There first needs to be a discordant coast, where there are alternating hard rock and soft rock. When the waves erode the headlands through hydraulic action and abrasion, the hard rock erodes much slower than the soft rock. After a long time of the waves crashing, the soft rock will have now moved much more inwards while the hard rock would still roughly maintain its shape but may have softer edges around them. The soft rock is the area of the bays and the headlands are the area of the hard rock.
How are Caves, Arches, Stacks and Stumps formed?
For them to form you first need a headland, inside the headland there must be some area of weakness. This can be some sort of crack or a different type of rock. The sea will now start attacking this weakness through refraction, (the waves bending around the Headland and hitting the sides of it) hydraulic action (where the force of the large waves puts more air into the cracks of the weaknesses) and abrasion ( where materials from the waves hit the weakness at high velocity. Eventually as erosion keeps on happening, the cave becomes bigger and bigger, it’ll eventually go through the headland as it will extend across to the other side of the headland, when that occurs an arch will form. The roof of the arch is very unstable, the more bigger the arch, the more unstable. Eventually due to weathering and erosion, it becomes possible that the roof of this arch collapses into the sea. When this occurs, this leaves behind a standing section of the rock and we call this a stack. The base of the stack is vulnerable to various types of erosion such as hydraulic action and abrasion (as mentioned before) because of the erosion from the waves, the base gets narrower and narrower and eventually, during a very large wave or a huge storm, the stack can collapse and what is left of it is called a stump.
What is a bar
A long stretch of sand stretches across a bay leaving a lagoon behind
What is a spit?
A long stretch of sand across a river mouth with one end attached to the mainland
Explain long shore drift
Eroded material is left on the beach, The waves from the sea come onto the beach at an angle and pick the material up and move them up the beach. This movement of the waves is called SWASH. The waves come in at an angle due to wind direction. The waves then move back down the beach in a straight direction due to gravity. They take other eroded material with them. This movement of the water back down the beach is called BACKWASH. This process is repeated again and again, which makes the material travel along the beach.
How is a spit formed?
Wind blows at angle causing longshore drift of material to occur along the coast. The coastline reaches a river mouth and LSD (Long shore drift) material is deposited across the mouth. Salt marsh forms behind the spit because the water is calm. The salt marsh joins the land behind to form part of the new coastline. The river water travels down the river. Wind blowing onto the spit curve the end of it. The river current stops the spit from being deposited right across the river mouth.
How is a Bar formed?
So first a spit is formed. This time there isn’t a lakemouth to prevent the spit from growing. So as Long shore drift keeps on depositing material on to the shore, it grows all the way until it connects 2 bays, also connecting two headlands. The water inside the lake is now called a lagoon, this area will gradually will be filled with deposition.
Hard engineering?
is the use of artificial structures aimed at controlling natural processes
Soft engineering?
is more environmentally friendly methods that work with natural processes
Managed retreat?
is when we allow the sea to flood and erode some land as a controlled retreat of the coastline
2 examples of Hard engineering to prevent erosion
Sea walls - 5000 to 10000 pounds per metre, a concrete or rock barrier is paced st the foot of cliffs or the top of a beach. It has a curved face to reflect the force of the waves back into sea.
Advantages: Effective at preventing erosion. Creates a promenade so people can walk along it.
Disadvantages: Extremely natural and ugly, obstructs beach access
Rock armour - 1000 to 4000 pounds per meter, are large boulders interlocked together to form rock revetments can be used to control erosion by armouring the beach face and dissipating wave energy by absorbing the wave energy.
Advantages: Rock armour is considered one of the best ways to maintain coastline as they absorb the energy of the waves
Disadvantages: They look different to the local geology, as the rock has been imported from other areas. In extreme weather conditions rock armor can fail.
2 examples of soft engineering to prevent erosion
Dune fencing- 400 to 2000 pounds per meter, Dune fencing is a coastal management technique used to trap windblown sand and encourage the formation or stabilization of dunes. These fences are typically made of permeable materials like woven synthetic mesh or wood, allowing sand to pass through while slowing down the wind and reducing its erosive power.
Advantages: Dune fences have been seen to look good on beaches, they are cheap, allows for a habitat to be created: an ecosystem.
Disadvantages: You need to maintain dune fencing a lot, won’t work in extreme weathers.
Beach nourishment is a coastal management technique that involves replenishing sand to beaches that have been eroded by natural processes or human activities. This process typically involves dredging sand from offshore locations and pumping it onto the beach.
Advantages: Nourished beaches can provide improved recreational opportunities for visitors, boosting local tourism economies. Beaches act as natural buffers against storm surges, and beach nourishment can enhance this protection.
Disadvantages: Temporary solution, can affect coastal ecosystems
