Deck 18a- Erosional processes and landforms Flashcards
What is erosion?
Erosion is the wearing away of rock along the coastline.
What are the 4 types of erosion?
Hydraulic action, solution (corrosion), abrasion and attrition
What is hydraulic action?
When a wave impacts a cliff face, air is forced into cracks under high
pressure, widening them. Over long periods of time, the growing cracks destabilise the cliff
and fragments of rock break off it.
What is abrasion?
The repeated action of waves breaking on a cliff is enough to remove material
from it over time. If sand and shingle are present in the water, it will act like sandpaper and
erosion will take place faster.
What is attrition?
Beach material is knocked together in water reducing their size and increasing
their roundness and smoothness.
What is solution erosion?
Carbon dioxide in the atmosphere is dissolved into water turning it
into a weak carbonic acid. Sea water also contains carbonic acid. The carbonic acid dissolves the carbonate ions in the rocks.
Which types of rocks are most vulnerable to solution erosion?
Rocks rich in carbonates ions (i.e. fossils) such as chalk and limestone
State an example of a local erosional coastline.
Marsden Bay, South Shields
How does a wave cut notch form?
The foot of a cliff is attacked by the action of the waves at high tide. Erosional processes such as hydraulic action, corrosion and abrasion erode the foot of the cliff, creating a wave cut notch.
How does a wave cut platform form?
Erosional processes continue to erode a wave cut notch deeper into the cliff, leaving an overhang. The overhanging rock eventually collapses under the force of gravity, causing the cliff to retreat. The retreating rock leaves a wave cut platform, which is the very base of the cliff which is not eroded as it is below the low water mark.
State an example of a local wave cut platform an which beach it is at.
Trow Point, South Shields
How are caves formed?
Coastlines that have weaknesses such as joints, bedding planes and faults are prone to hydraulic action which will widen the weakness into a crack. Hydraulic action and abrasion will continue to erode and widen the crack leading to the formation of cave.
How are arches formed?
Waves will be refracted and focussed on all sides of the headland allowing erosional processes to deepen caves. When two caves are aligned and arch can form where they meet. Erosion at the base widens the arch.
What is a stack and how are they formed
A stack is a pillar of rock that is separate from the main cliff along a coastline. Over time arches become unstable due to continued erosion at the base and sub aerial processes above the sea surface. When an arch collapses a stack is formed.
What is a stump and how are they formed?
A stump is a remnant stack. Erosional and subaerial processes continue to wear away a stack until it collapse leaving behind a stump.
State an example of a local beach that is characterised by erosional landforms following the crack-cave-arch-stack-stump sequence.
Marsden Bay, South Shields
Old Harry’s Rocks in Dorset is another good example of this sequence.
What is a geo and how are they formed?
A geo is a narrow, steep sided inlet that forms when the sea cuts inland, along a joint.
What is a blowhole and how are they formed?
A blowhole is a vertical opening or chimney in the roof of a sea cave, or a crack in a coastal cliff, through which air and water are forcefully ejected by the action of waves and tides, creating a spray or jet of water. They are formed when erosion is vertical, often due to lots of solution erosion.
