Erosional Landforms Flashcards
Landforms and Landscapes
Landform ~ a small - scale feature.
Landscape ~ made up of these small features and explains how they are interconnected with each other and coastal processes.
Headlands and Bays
Formed where there are bands of different rocks with different resistance to erosion.
Formed mainly by hydraulic action , wave pounding and abrasion
where rocks lie PERPENDICULAR :
- the weaker rock erodes more quickly forming a bay
-the more resistant rock juts out as a headland.
- discordant coastline
where rocks lie PARALLEL:
- hard rock lies on the seaward side of the coastline
- bays develop when a weakness is eroded landward
- concordant coastline.
Wave refraction
A process by which waves break onto an irregular shaped coastline ~ headland separated by two bays.
- Waves drag in the shallow water approaching a headland
- The wave moves faster in the deeper water approaching a bay , causing the wave to REFRACT.
- causes the energy of the waves to be concentrated or CONVERGED at the headland , causing higher waves and greater EROSION.
- The low energy wave spreads out or DIVERGE into bay area causing shorter waves and greater DEPOSITION.
Wave - cut notch
- DESTRUCTIVE WAVES break repeatedly on coastlines.
- UNDERCUTTING occurs between high and low tide.
- Marine processes of hydraulic action , wave pounding and abrasion form a WAVE - CUT NOTCH at the base of the cliff.
- CONTINUED undercutting , increases the DEPTH of the notch, and weakens the support for rocks above.
- This eventually COLLAPSES , producing a STEEP CLIFF profile.
- REPEATS over time , and the cliffs retreat inland , parallel to the coastline.
Wave - cut platform
- The landform produced due to the continuous sequence of undercutting , collapsing and retreating.
- At the base of the steep cliff, a GENTLY SLOPING SHELF appears ( 0 - 3 degrees )
- Often STRIATED ( marked with long , thin lines ) from rocks being dragged over the surface.
- ROCK POOLS form due to abrasion and biological weathering .
- MATERIAL is dragged across it by WAVE ACTION and is cut into by abrasion , hydraulic action and solution.
- At LOW TIDE ~ subjected to weathering processes. Example ~ freeze thaw .
- WIDEN ~ causing shallow water and small waves even at high tide.
- FRICTION slows down approaching waves so they break on the platform and not at the base of the cliff , so undercutting eventually CEASES.
Geos
- Narrow , steep sided inlets , formed when vertical lines of weakness ( faults ) in rocks run PERPENDICULAR to the coastline.
- Formed by HORIZONTAL HYDRAULIC ACTION .
- The faults become larger and turn into narrow, tunnel-like caves.
- Eventually the roof of the cave collapses leaving behind the narrow inlet.
Blowhole
- occur in a similar way to geos.
- Horizontal faults in rock become enlarged into caves.
- If a major fault line runs vertically through the ROOF of the cave , then water can be forced upwards during storm conditions.
- VERTICAL HYDRAULIC ACTION create a tunnel to the surface.
- Eventually water is forced out of the top of the cliff, as the waves break on the coastline.
caves , arches , stacks and stumps
- A sequence of erosional landforms
- often develop around headlands where wave action is concentrated due to wave fraction.
- develop in areas of more RESISTANT ROCK.
- CRACKS form in the base of the cliff due to HYDRAULIC ACTION.
- Cracks are further widened by WEATHERING PROCESSES.
3.Over time cracks form WAVE-CUT NOTCHES.
- ABRASION and HYDRAULIC ACTION deepen the notch to form a CAVE.
5.WAVE FRACTION causes destructive waves to concentrate their energy on the sides , DEEPENING the cave.
6.If two caves are ALIGNED , the waves may cut through to form an ARCH.
- Overtime the arch becomes UNSTABLE and collapses under its own weight to form a pillar of rock called a STACK.
- The stack is eroded at its base and weakened by SUB ERIAL PROCESSES from above.
- Eventually the stack collapses to from a STUMP, which is eroded by ATTRITION and transported away to be deposited within the bay.
