Geography KA1

Key Words

• coastline = the part of a coast where land meets the sea. erosion helps to make tis line more clear and beaches are often found there
• constructive waves = low lying waves with crests far apart. they have a gently flowing wave fronts and carry sediment up the beach
• destructive waves = close waves with high, steep wave crests and fronts. breaking waves plunge onto the beach with little swash but a strong backwash, carrying sediment away from the sea
• swash = the water that travels up the beach when the wave hits land
• backwash = the returning water from the swash going back into the sea

Erosion, transportation and deposition

• Solution = dissolving of chemicals in rock eg. limestone
• corrosion = rock fragment picked up be the sea are thrown at a cliff. they scrap and ware away rock
• abrasion = sediment grinding on a rocky platform
• attrition = Rock fragment carried out to sea and grinned against each other (made into sand)
• hydraulic action = power of the waves as they hit a cliff. trapped air is forced into cracks, eventually causing them to break apart
• Long-Shaw drift (transportation) = prevailing winds cause waves to carry back sediment in a strong backwash at a right angle then more waves to carry it along the shaw at an angle and the process repeats, carting sediment along the shaw.
• deposition = takes place when the flow of water slows down and sediment can't be carried any more so is dropped/deposited. this occurs commonly on bays

Weathering & Mass Movement

• Weathering
• mechanical weathering = the disintegration of rocks. Where this happens, piles of rock fragments called screen be found at the foot of cliffs.
• chemical weathering = caused by chemical changes. Rainwater, which is slightly acidic, very slowly disintegrates certain types of rocks and minerals.
• freeze-thaw action = in the day, water collects in cracks in the rocks. At night, the water freezes to form ice and expands and causes stress, and the cracks enlarge. After being repeated over a large amount of time, rock fragment breaks off and collects as scree at the foot of the rock face.
• Mass Movement
• it is the downslope movement of rocks, soil or mud under the influence of gravity
• There are several types of movement:
• rock slides = on a steep-is slope, rock breaks apart and slides down a glide plane, and at the impact point at the bottom, the rock breaks into debris, along with more debris from previous rock slides
• Mud slides = on a steep-is slope, weathered loose material mixes with water and slides down a hill as mud.
• Slumping = has a concave slip plane so material is rotated back into the cliff face as it slips.
• Slides = these take place on steep cliff faces. Weathering has taken place on the sides and there are joints and cracks in the bedding planes. There is scree at the bottom.

Wave Cut Platforms

• over time, during a medium tide mainly, destructive waves erode a cliff and create a wave cut platform, and after it becomes so deep in, the rest of the cliff face above it crashes down to forms debris
• the bottom of the cliff doesn't usually get eroded but becomes soft because of the friction because of the swash and backwash.

Headlands and bays (Conc. & dis.cord.)

• discordant coastline: occurs when bands of different rock type run perpendicular to the coast
• concordant coastline: Occurs where the bands of existing rock types run panel to the coast. the harder rocks act as a warrior to prevent erosion on the softer rocks further inland
• Headlands: hard rock that stick out of discordant coastlines as they haven't been eroded, like the soft rock has (eg. Dorset, Old Harry Rocks)
• Bays: where soft rocks have been eroded, bays form and waves deposit sediment which can form beaches. Bays are also sheltered.

Coastal Erosion/Deposition Landforms

• spit: deposition drops sediment just off a shaw and with long-shaw drift, it builds up over time, forming a spit. they can get multiple recurved ends as it gets longer and in the sheltered areas, salt mash can form
• bars: this blocks off the river or opening and forms a lagoon from where a spit has grown to the other end of the land, creating a bar shape, where no water can pass through
• headlands
• bays
• caves: cracks open and form caves
• arch: erosion may lead to 2 back to back caves, creating an arch
• stack: arch collapses from weathering
• stump: stack erodes and is weathered to form a stump