2.2 The main landforms associated with these processes
2.2.1 The characteristics and formation of landforms: headlands, bays, cliffs, wave-cut platforms, caves,
arches, stacks, stumps, beaches, spits, bars, sand dunes.
2.2.2 The formation and characteristics of discordant and concordant coastlines.
2.2.1 The characteristics and formation of landforms: headlands, bays, cliffs, wave-cut platforms, caves,
arches, stacks, stumps, beaches, spits, bars, sand dunes.
2.2.2 The formation and characteristics of discordant and concordant coastlines.
2.2.1 The characteristics and formation of landforms
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Part 1 - Erosional Features
Coastal erosion is the process by which waves wear away and remove rock from the coastline. The energy of waves, particularly during storms, can gradually break down cliffs and other coastal features over time. Erosion is most effective where waves are powerful and rocks are less resistant. You have previously studied the impacts of destructive waves and also the four key processes of coastal erosion, namely: |
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Hydraulic action – the force of waves compresses air into cracks in the rock, causing pieces to break away.
Abrasion (corrasion) – sand, pebbles and rocks carried by waves are thrown against the coast, wearing it away like sandpaper.
Attrition – rocks carried by waves collide with each other, becoming smaller, smoother and rounder.
Solution (corrosion) – acidic seawater dissolves soluble rocks such as limestone and chalk.
Over thousands of years, these processes create a range of distinctive coastal landforms, including headlands, bays, cliffs, wave-cut platforms, caves, arches, stacks and stumps.
Abrasion (corrasion) – sand, pebbles and rocks carried by waves are thrown against the coast, wearing it away like sandpaper.
Attrition – rocks carried by waves collide with each other, becoming smaller, smoother and rounder.
Solution (corrosion) – acidic seawater dissolves soluble rocks such as limestone and chalk.
Over thousands of years, these processes create a range of distinctive coastal landforms, including headlands, bays, cliffs, wave-cut platforms, caves, arches, stacks and stumps.
Bays & Headlands
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Bays and headlands are formed in a similar way to rapids in rivers. They develop along coastlines where there are alternating bands of hard and soft rock running at right angles to the coast. The softer rock is eroded more quickly by the sea, creating a bay, while the more resistant hard rock is left jutting out into the sea as a headland.
Bay A bay is an indented section of coastline that is usually found between two headlands. Bays are generally more sheltered from wave attack, so there is less erosion. As a result, beaches often form in bays as sediment is deposited. Headland A headland is a piece of land that extends out into the sea. Waves are concentrated on headlands by wave refraction, resulting in higher rates of erosion. This can lead to the formation of coastal features such as caves, arches, stacks and stumps. Watch - Play the video above from 2:20 to 4:35. This shows the process of headland and bay formation. Task 2 - Use the worksheet to explain the process and formation of bays and headlands. |
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Cliffs & Wave Cut Platforms
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Wave-cut platforms are formed in a similar way to waterfalls and gorges in rivers. At high tide, the power of the sea attacks and erodes the base of a cliff.
Over time, this erosion creates a wave-cut notch (an undercut section at the bottom of the cliff). As the wave-cut notch becomes larger, the weight of the rock above it increases. Eventually, the cliff can no longer support its own weight and collapses. The process then begins again, as wave erosion creates a new wave-cut notch at the base of the cliff. As this cycle continues, the cliff gradually retreats inland. As the cliff retreats, a wave-cut platform (a broad area of exposed bedrock) is left behind. Wave-cut platforms are most visible at low tide. Task 3. Watch the video to the right, and this one. ii. Make a sketch of the image above onto the worksheet. iii. Annotate all the main features using the description above and information from the videos. |
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Caves, Arches, Stacks and Stumps
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Watch - Check out this excellent video from Time for Geography.
Caves, arches, stacks and stumps are usually found on headlands, where wave refraction concentrates wave energy and erosion. Waves exploit weaknesses in the rock, such as cracks and joints. Hydraulic action is often the main process of erosion involved, although abrasion may also play a role. Over time, a crack may widen to form a cave. As erosion continues, the cave becomes larger and may eventually cut all the way through the headland, creating an arch. As the arch continues to widen, the weight of the rock above becomes too great and the roof collapses, leaving behind a stack. The stack is then attacked by erosion at its base and weathered from above. Eventually, it collapses, leaving a stump, which is often only visible at low tide. Task 4 - Use the worksheet to the right to create an annotated sketch using the diagrams, YouTube video and descriptions above to explain how caves, arches, stacks & stumps form. |
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Part 1 - Depositional Features
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Beach: A beach is an accumulation of sediment between the lowest low tide and the highest high tide. Beaches may be composed of sand, shingle, pebbles or a mixture of these materials. Beach material can come from longshore drift, constructive waves, cliff erosion and river deposition.
Beaches can be divided into three main zones: the backshore, foreshore and offshore. The backshore is the area above the normal high-tide mark and is only reached by waves during storms or exceptionally high tides. The foreshore is the area between the high-tide and low-tide marks. The offshore zone is the area beyond the low-tide mark that is permanently covered by water. Berm: A berm is a ridge of sand or shingle found at the upper part of a beach. It is formed when constructive waves deposit sediment near the high-tide mark. Several berms may develop over time, representing different periods of deposition. Intertidal Zone: The area of the coastline between the high-tide mark and the low-tide mark. This area is covered by seawater at high tide and exposed at low tide. Strand Line: A line of material such as seaweed, driftwood, shells and litter that has been deposited by the sea at the highest point reached by a particular tide. |
Check out the photo above of a beach in Conwy, UK and see if you can spot any of the features in the diagram above.
Task 5 - Now complete the worksheet below. |
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Spits & Bars
Spits and bars are coastal landforms created by the deposition of sediment. Their formation is closely linked to longshore drift, the process by which waves transport sand and shingle along the coastline. When the coastline changes direction or crosses the mouth of a river or bay, longshore drift may continue depositing sediment out to sea. Over time, this can create a spit, which is a narrow ridge of sand or shingle attached to the land at one end. If deposition continues and the spit grows across an entire bay, joining two headlands, it forms a bar. Bars can cut off a bay from the sea, creating a lagoon behind them. Spits and bars are excellent examples of how coastal deposition can reshape coastlines and create new landforms. Watch - Play the two minute explanation video on the YouTube video to the right. Task 5 - Complete the worksheet by labeling the coastal processes leading to the formation of Hurst Spit (UK) as well as its physical features using information from the video task. |
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Bars (no, not that sort!)
Task 6 - Complete the worksheet below using the Google Map to help you.
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Sand Dunes
Sand dunes are depositional coastal landforms formed by the accumulation of sand above the high-tide mark. They are created when dry sand is blown inland by the wind from a beach and becomes trapped by obstacles such as driftwood, pebbles or vegetation. As more sand is deposited, small mounds begin to form. These mounds gradually grow into dunes as additional sand accumulates. Plants such as marram grass (see photo to the right) help to stabilise the dunes by trapping more sand with their leaves and roots. Sand dunes are an important part of the coastal system because they act as natural barriers against erosion and flooding, while also providing valuable habitats for plants and animals. Watch: Play the first three minutes of this video, from Time for Geography (note the subtitle language options). Task 7 - Using the rest of the Time For Geography video, complete the tasks on the worksheet. |
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2.2.2 Discordant and concordant coastlines.
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The shape of a coastline is influenced not only by the power of the waves but also by the arrangement of the rocks along the coast.
Many coastlines are made up of alternating bands of hard and soft rock. The way these bands are arranged in relation to the sea determines whether the coastline is described as discordant or concordant. A discordant coastline occurs when bands of hard and soft rock run at right angles (90°) to the coastline. The softer rock is eroded more quickly than the harder rock, creating bays and headlands. A concordant coastline occurs when bands of rock run parallel to the coastline. If the outer band of hard rock is breached by erosion, the softer rock behind it can be rapidly eroded, creating features such as coves. The arrangement of rock types therefore plays an important role in determining the shape and characteristics of coastal landscapes. Task 8 - Complete the activities on the worksheet. |
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