Spatial Variations at Muriwai
There are four key areas where differences in Natural Processes occur
Otakamiro Headland
Beach
Southern Dunes
Northern Dunes
1. Natural Process: Wave Erosion
Headland
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Due to wave attack, hydraulic pressure and abrasion erosion occurs at the headland
Wave attack attack has created a notch at the base of the north side of the headland
Headland made up of voclanic rock and awhitu sandstone. Awhitu erodes more easily than the
harder volcanic rock
Awhitu stone used by waves to further erode through abrasion
Southern Dunes
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Waves reach the base of the southern dunes
Due to the steep shape of the dunes (10-12 metres) and the lack of vegetation the waves cut
into the base of the dunes causing it to erode onto itself
Northern Dunes
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In times of extreme low pressure the Mean High Tide mark reaches to the foot of the dunes
Due to shape of dunes (rolling 2-3 metres high) and vegetation growth the northern dunes do
not experience as much erosion as the southern dunes whilst wave attack does cut into the base
of the dune it does not collapse onto itself as extreme as the southern dunes (due to vegetation
growth and lack of incline of dune shape)
2. Natural Process: Wave transportation of sediment
Headland
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Wave refraction causes eroded material from the headland to be taken towards the beach
Transportation of sediment driven by currents being powered by prevailing south west winds
Southern Dunes
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Since the 1950s pattern has been that more material is lost to the sea than deposited by
Aeolian or wave processes
Beach
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Longshore drift transports sediment up the beach in a zig-zag fashion
850,000m³ of material moved up beach annually
3. Natural Process: Wave deposition of material
Headland
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Little deposition of material (except in caves) as wave attack transports material at the
headland rather than depositing
Beach
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Material is deposited on beach due to Longshore drift
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Aeolian processes continue transport & deposition of material towards dunes
Northern & Southern Dunes
Waves deposit little material on dunes
Instead waves remove material from dunes
4. Natural Process: Aeolian Erosion
Headland
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Headland wet by waves is in turn dried by wind
This leads to salt crystallisation on the headland
Further wind leads to erosion of headland material
Southern Dunes
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Wind leads to blow outs and erosion of southern dunes
Little vegetation cover exposes southern dunes more
Headland acts as a shelter from wind
Northern Dunes
I) More exposed to wind than southern dunes
II) Extensive vegetation cover means these areas suffer less wind erosion
III)
Areas of little vegetation cover and directly in face of south west winds suffer blow
outs
Beach
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South west winds can loosen sand on beach and cause erosion
5. Natural Process: Aeolian Transportation
Headland
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Can move fine material from rock surface into the sea
Loosened material from wave attack can be blown into sea
Frittering
Beach
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Off shore breezes over 18Km/ph allow transportation of material (Saltation, Surface creep) up
the beach towards the dunes
Northern Dunes
• Wind transportation occurs with sea side face of dune more exposed to the winds
6. Natural Process: Aeolian Deposition
Headland
• No deposition
Beaches
• Material that is unable to reach the dunes will accumulate on the beach
Northern Dunes
• Wind deposition will occur due to saltation and surface creep
QUESTION
Explain how the natural processes operating within your geographic environment have affected the
distribution of the natural phenomena.
STRUCTURE
Intro Paragraph 1 (P1)
There are a range of natural processes that are active in Muriwai Coastal Geographic Environment
(M.C.G.E). Theses natural processes are present in the 4 main areas in Muriwai; Otakamiro Headland,
Beach, Southern and Northern Dunes. Within these areas certain Natural Processes are more dominant
than others. At the Headland the dominant natural processes is wave erosion (P2). At the Beach it is
Longshore Drift (P3). Northern Dunes it is Aeolian Processes (P4). At the Southern Dunes it is a
combination of Aeolian and Wave Processes (P5). In my essay I will discuss each area and how natural
processes affect natural phenomena at M.C.G.E.
Conclusion (P6)
QUESTION
Select two natural processes and name them. Draw a labelled map(s) and/ or cross section (s) to
show spatial variation in the operation of each of these 2 natural processes within your Geographic
Environment. Refer to the 2 natural processes and Account for spatial variation in the operation of
each of these natural processes within your Geographic environment.
STRUCTURE
Notes- 2 part Question
IV) Choose 2 natural processes that demonstrate spatial variation (basically choose the ones you
can write the most about) and highlight these in a basic map of Muriwai (Remember to include
all relevant mapping conventions).
V) Requires that you write an essay explaining why spatial variation occurs in each of your named
natural processes.
Essay
Intro Paragraph 1 (P1)
There are numerous examples of spatial variation that occur in the Natural processes at Muriwai
Coastal Geographic Environment (M.C.G.E.). Wave Erosion and Aeolian Erosion are good examples of how
natural processes vary spatially. These variations occur within the 4 main regions at M.C.G.E;
Otakamiro Headland, Beach, Southern and Northern Dunes. At the headland Wave Erosion occurs in
the form of Hydraulic Action and Corrasion (P2), there is little to no erosion on the beach or at
Northern Dunes (P3) where as the Southern Dunes the main process is Wave Encroachment (P4).
Spatial variation is further shown in Aeolian Erosion. At the headland Aeolian Erosion occurs in the
form of Frittering (P5), there is little to no erosion the beach (P6). However at the Southern Dunes
the main process is Deflation (P7).
Conclusion (P8)
Remember where possible include labelled diagrams