1. A/S outline + Where is the natural environment, what is it like, what natural features (landforms) are there and where are they located (distribution)?
Lesson one

2. Demonstrate understanding of how interacting processes shape a NZ Geographic environment External exam
Where is the natural environment, what is it like, what natural features (landforms) are there and where are they located (distribution)?
What natural processes are interacting to form the landforms (outcomes) and what are the interactions involved? What is the scale of these processes (individual event, seasonal, short term, long term or over geological timescale)?
How and why do these processes show temporal variations?
How and why do these processes show spatial variations?
How and why is the environment being modified at the present and is it likely to be changed in the future?

3. Omaha natural environment
Where is Omaha?

4. Where is the natural environment?
Location and Extent:
60km N of Auckland, on the East coast
36*20’ 26” S 174* 46’ 30” E
Sand Spit 4kms long, orientated N-S, between 2 rocky headlands, Ti Point to the N and Karamuroa Point/Te Kie point to the S.
The Whangateau Harbour entrance separates the spit from Ti Point.
The northenmost end of the spit is called Te Taumutu Point.

5. Mapping activity

6. Location

7. Oblique aerial photograph

8. Origins of the sand spit
The sand spit was formed 6,500 yrs ago after the last ice-age ( sea levels 100m lower and freeze-thaw weathering broke up rocks). Sands were transported shoreward from the Hauraki Gulf by rising sea levels.
Sand spit formed by ocean currents depositing sand in slack water in a Northerly direction from Te Kie point.
Over the last 100yrs sea levels have continued to rise by approx 13-14cm.

10. What are the natural features? Where are they located?
Ocean beach: Dunes, fore dunes and back dunes Sand ripples/beach cusps Berm marking at high water mark

11. Ocean Beach: dunes
Back dunes
Fore dunes

12. Ocean Beach

13. Ocean Beach: sand ripples/beach cusps

14. Ocean Beach: berm marking at high water mark

15. What are the natural features? Where are they located?
Ti Kie Point/Ti Point: Cliffs/headland Shore platform

16. Ti Kie Point/Ti Point: Cliffs/headland

17. Ti Kie Point/Ti Point: shore platform

18. Cliff with shore Platform
Waitemata sandstone
Greywacke
Shore Platform

19. Features of Mangatawhiri Sand Spit
(1) beach of sand composed of quartz and feldspar between 20 and 100m wide
(2) longitudinal sand dunes 1-4m high with spinifex, pingao, and marram grasses on the fore dunes, and lupins, pohuehue and shrubs on the back dunes. Dune ridges run parallel to the beach and have steep windward slopes-(20*) and gentler leeward slopes (5*).
Sand ripples and beach cusps can be seen on the northern beach.
The Northern part is a bird reserve of 8 hectares.

20. Features of Mangatawhiri Sand Spit
(3) At the southern end of the beach, Te Kie Point is a cliff, 20-50m high of Waitemata sandstones and mudstones with
(4) a horizontal shore platform at the base of the cliff, up to 100m wide of darker, harder greywacke.
(5) North of the Whanateau harbour, Ti Point is a headland of olivine basalt.

21. Drawing a precis sketch
A precis sketch is a simplified drawing of an area showing only “points of interest” to you and your reader – in our case a precis sketch of natural features at Muriwai.
Use definite lines and do not use shading.
Divide your picture into 3 parts: background, middle ground and foreground. Draw one part in entirety at a time.
Features in the background are smaller and darker (to show darkness draw diagonal lines really close together).
Features in the foreground look larger and are lighter (to show lightness draw a few diagonal lines).
Do not include moving objects like cars, people or gannets.
Include a title, frame and labels (use a ruler and write the name of the feature neatly).

22. Draw a precis sketch of this view

23. Elements and natural processes (1)
Lesson 2

24. Do now
Name 2 features at Ocean Beach
Name 2 features at Te Kie Point

25. Do now Name 2 features at Ocean Beach Ocean beach:
Dunes, fore dunes and back dunes
Sand ripples/beach cusps
Berm marking at high water mark
Name 2 features at Te Kie Point
Cliffs/headland
Shore platform

26. Do now
Describe the location, size and extent of the Omaha coastal environment

27. Do now
Describe the location, size and extent of the Omaha coastal environment
Location:
60km N of Auckland, on the East coast *20’ 26” S 174* 46’ 30”
Extent:
The limit of Little Omaha Bay (Ocean Beach) is Ti Point in the North and Karauroa Point in the South. The Whangateau Harbour entrance separates the spit from Ti Point. The northenmost end of the spit is called Te Taumutu Point.
Size:
Sand Spit 4kms long, orientated N-S, between 2 rocky headlands

28. Definitions - how many do you know?
Cliff
Bay
Esturary
Spit
Beach

29. Definitions - how many do you know?
Cliff
A steep rock face along the coastline
Bay
Indents in the coastline between two headlands
Estuary
The part of the wide lower course of a river where its current is met by the tides

30. Definitions - how many do you know?
Spit
A ridge of sand deposited parallel to the coast by long shore drift
Beach
The area of deposited sediment between the lowest spring tide level and the point reached by the storm waves in the highest tides

31. To know what the natural processes are, we need to know what the individual elements are that work to form processes.
What could be some examples of elements?

33. 1. Inputs/Elements Write these on handout
Inputs: winds NE to SE
: waves NE to SE
: tides m. Into the harbour (flood) and out (ebb) of harbour
: sand fine (0.17mm)- (0.3mm) to medium-coarser at harbour entrance-high feldspar content=volcanic origin from central N Island via Waikato R. through Hauraki Plains.
: base rock- greywacke with Waitemata Sandstone on top Ti Point-olivine basalt intrusion-hard rock but jointed, Karamuroa-sandstone
: vegetation: marram, spinifex, pingao
: sunshine
: rain

34. How to measure wind?

36. WAVES wave length crest trough wave height
particles in waves follow a circular pattern
Waves are measured as wave length from wave crest to crest
Wave height is measured from trough to crest

37. Copy and draw a diagram
Waves transfer energy from one place to another as the water particles move forward in a circular motion. The water itself will rise and fall with the movement of the wave. Waves at sea are created by the transfer of energy from wind to the sea surface.

38. Copy and draw a diagram
As the waves approach Te Kie Point, the sea becomes shallow and the base of the wave is slowed down by frictional drag. In turn, the wave crest becomes higher and the wave length shorter. When the wave height is greater than the wave depth, the crest breaks. As Te Kie Point, a headland, juts out into the sea, the wave breaks directly on the headland at high tide.

40. Wave Types

41. TIDES Are daily changes in sea levels
Tides rise (FLOOD) to produce a HIGH TIDE
And fall (EBB) (LOW TIDE)
Produced by the gravitational pull that the Sun and Moon exert on the Earth’s surface and the oceans on 1 side and the other side bulges out because of inertia
there are two high tides on Earth at any one time
Moon/
Sun

43. Can you think of any examples of natural processes?

45. 2. Natural processes Write these on handout
1 Past volcanic processes and past weathering (frost-shattering during peri-glacial times) to produce the sand.
2 Processes that erode or wear away the rocks.
Weathering (salt crystal growth and exfoliation) and
Mass Wasting (rock falls, landslides)
Wave erosion (by destructive waves), wave quarrying, hydraulic action (30 tonnes per m2), abrasion, attrition.
Wave Refraction around Te Kie Point
3 Processes that deposit or build up the beach.
Wave transportation ( longshore drift ) and wave deposition by constructive waves pushing sand up the beach in the swash.
Wind (Aeolian) transportation by saltation, surface creep and suspension and wind deposition when the wind drops or sand hits vegetation, fence etc.

46. Processes that erode rocks - weathering
exfoliation Exfoliation occurs where there is alternative heating of the rock during the day and cooling during the night. This results in the expansion and contraction of the rock which weakens the sandstone. The outer layers brake off as concentric layers.

47. Exfoliation or Onion Weathering

48. Processes that erode rocks - weathering
Salt crystalisation
Salt crystals attack porous, coarsely granular rock.
Saline water enters pores and as it evaporates salt crystals form.
As they grow pressure is put on the rock, or the rock is dissolved and/or split by incoming water.

49. Processes that erode rocks - weathering
Mass wasting (rock falls, landslides) Is the removal of material downslope and occurs due to gravity. This allows soil and rock to fall down the steep slopes and form a scree slope at the bottom where it accumulates

50. Elements and natural processes (2)
Lesson 3

51. Processes that erode rocks
Wave erosion (by destructive waves), wave pounding, hydraulic action, abrasion, attrition.
Abrasion
This is caused by boulders, pebbles and sand being hurled against the base of the cliff by breaking waves. This results in rock breakup.
When a cliff consists of differing layers of rock of differing resistance, the less resistant rocks are eroded away rapidly, while the more resistant rock remains.
Draw a diagram

52. Waves carrying sand, shingle is hurled at the cliff

53. Processes that erode rocks
Wave erosion (by destructive waves), wave pounding, hydraulic action, abrasion, attrition.
Hydraulic action
When water is thrown against a cliff by breaking waves it often compresses the air in cracks and crevices in the rocks. When the waves retreat the air expands, sometimes explosively. This causes rocks to shatter as the cracks are enlarged and extended.
Draw a diagram

54. Air can become compressed and will expand when the wave retreats

55. Processes that erode rocks
Wave erosion (by destructive waves), wave pounding, hydraulic action, abrasion, attrition.
Attrition
As boulders and rocks, already eroded from cliffs, are hurled against the shore, and against each other by breaking waves, they gradually break down into smaller and more rounded pieces.
Takes place along side other erosional processes
Accounts for the varying sediment sizes
Draw a diagram

56. Break down of sediment on the shore

57. Processes that erode rocks
Wave erosion (by destructive waves), wave pounding, hydraulic action, abrasion, attrition.
Wave pounding
Steep waves have considerable energy. When they break as they hit the foot of cliffs or sea walls, they may generate shock-waves, which may produce pressures of up to 30 tonnes per square metre.
Draw a diagram

58. Sheer force

59. Processes that erode rocks
Wave refraction
Process by which waves undergo a change of direction as they approach headlands and beaches.
Generally most beaches are concave towards the sea. This is due to wave refraction.

60. Wave refraction
Close to the coast, water gets more shallow and waves are slowed down. This causes the waves to bend around Te Kie Point, concentrating the wave energy and making it possible for the waves to attack all sides of a headland.
On Ocean Beach, because the beach is concave, the waves spread out as they slow down and the energy is dissipated.

61. As a wave approaches a headland
Water depth decreases, causing that section of the wave to slow down due to friction from the sea floor
The change in speed causes the remaining deep water wave section to refract (bend) towards the headland.

62. Coastal Kung Fu

63. 1 2
Rockfalls 3
Wave action

64. Relief: Omaha climate graph/ wind rose?
Lesson 4

65. Elements and natural processes (3)
Lesson 5

66. Beaches
Beaches are the most unlikely of landforms to be found facing the open sea.
They are, after all, merely piles of loose sand and shingle and yet they manage to remain intact on coastlines where waves can reduce concrete sea walls to rubble in a very short time.
The secret of their geomorphic success lies, of course, in this very fact-that they are only loose sand.
Beaches can both adapt their shape very quickly to changes in wave energy and also dissipate this energy in minor adjustments of the position of sand or shingle.
The beach is therefore able to maintain itself in a dynamic equilibrium with its environment due to the inherent mobility of its sediments.
Pethick, 1984

67. Processes that deposit or build up at the beach
Wave transportation ( longshore drift ) and wave deposition by constructive waves pushing sand up the beach in the swash.
Write/guess definitions for
Wave transportation
Longshore drift
Wave deposition

68. Wave Types

69. Longshore Drift- Wave Transportation
Swash - water sliding up beach at the same angle as the wave approaches the shore
Backwash - water flowing back down beach to sea at 90’ to the beach.
This transports sand along the beach. Omaha, sand deposition to S of Southern Groyne suggests S to N movement.

71. Processes that deposit or build up at the beach
Wind transportation and deposition by saltation, surface creep and suspension
The movement of sand in air is a highly complex process.
Airflow (wind) experiences frictional drag over a sand surface (beach), therefore the airflow slows down i.e. there is a decrease in wind velocity.
The beach surface should be visualised as a continous layer of sand grains with a superfacial scattering of individual grains lying on it. This upper layer consists of grains with a range of diameters which project (poke up) through the air flow.

72. Processes that deposit or build up at the beach
Wind transportation and deposition by saltation, surface creep and suspension
Surface creep
Wind rises to a minimum of 4.5m/s in speed
Sand is rolled along the surface
Saltation
Wind speed increases to 5m/s
Sand is picked up into the air briefly and then falls back due to gravity, striking the next grain which in turn is lifted into the air

73. Processes that deposit or build up at the beach
Wind transportation and deposition by saltation, surface creep and suspension
Suspension
Is found in very strong winds or if the sand grains are very small in dimension.
Sand grains are suspended in the air

74. wind direction BACKSLOPE SLIPFACE crest movement of sand
WIND TRANSPORTATION Movement of sand over dunes with no vegetation to trap sand.
wind direction
BACKSLOPE
SLIPFACE
crest
angle of repose
movement of sand

76. Beach Profile

77. Recap processes

78. What natural processes are interacting to form the landforms (outcomes) and what are the interactions involved?
Lesson 6

80. Looking at natural processes, which ones do you think interact?

81. The formation of ONE natural feature within a Coastal Geographic Environment: Sand Dunes Interaction between hydrological and aeolian processes
2 SE wind direction /waves approach Ocean beach from SE, transporting sand, less than 1mm diam. feldspar
and quartz, constructive waves( )
push sand up beach.= hydrological deposition
1 Longshore drift moves sand along the beach from s-n at 1m in 1 min.
=hydrological transportaion
3 SE wind picks up sand as it dries(saltation moves 80%) and blows it inland up the leeward slope of the dune and over the crest
(? m high)and down
the steeper slipface. = aeolian transportation and deposition

82. The formation of ONE natural feature within a Coastal Geographic Environment: Sand Dunes Interaction between hydrological and aeolian processes
From the diagram you have drawn, write a series of paragraphs to explain how two interacting processes have created a named landform feature

84. the cliff retreats The formation of ONE natural feature within a
3.Wave erosion (hydraulic action etc)
at H.tide erodes cliff, leaving shore
Platform ( ) of harder Greywacke
1.Sub-aerial weathering affects cliff shape so not 90*. Waitemata sst. ( ?m )
2.Undercutting of cliff
Causes collapse and
mass wasting
the cliff retreats
The formation of ONE natural feature within a
Coastal Geographic Environment:
Cliffs and Shore Platform

85. First of all… Notches
The most important erosional process is wave pounding.
As waves attack cliffs they undercut the cliff and form a notch.

86. When a cliff face can no longer be supported by its base, the cliff face collapses.
Material eroded from the cliff will be caught up in the wave action and will act abrasively- add a cutting compound of gravel and sands.
As the cliff face continues to be eroded away, as its less resistant rock is exposed, a shore platform will develop..
The shore platform will develop to a depth determined by the power of the wave.
Beyond the platform eroded material will be deposited.
The platform will become wide enough that waves will break well before the cliff, and the erosion on the cliff will decrease.
The shore platform, an area of resistant rock, will remain until erosional wave processes, or weathering, break it down.

87. Draw a series of diagrams to show how two interacting processes have created a named landform feature - Interacting processes = hydrological processes of wave refraction and wave pounding Remember to annotate Remember to include specific information

88. Field trip to Omaha
Lesson 7

89. Go through field trip booklet
Go through field trip booklet. Diagram of features/processes (How and why do these processes show spatial variations
Lesson 8

90. Map to show Spatial Pattern of Processes
Weathering, mass wasting and
wave erosion. Wave refraction
Wave transportation and deposition, aeolian
Transportation and deposition
Weathering, mass wasting and
wave erosion. Wave refraction

91. Map to show Spatial Pattern of Features or Outputs
1 Cliff
3 Beach
4 Fore and Back Dunes
1 Cliff
2 Shore Platform

92. How and why do these processes show temporal variations?
Lesson 9

93. Can you think of how the processes can change over time (temporal variation)
Weathering
Hydrological
Aeolian

94. Temporal Variations
Mangatawhiri spit was formed over the last 6,500yrs as the sea level rose m after the last ice-age, due to wave transportation and deposition.Aeolian processes have built up the dunes on the spit.
Summer storms, LP systems bring storm surges and large waves erode the beach eg TC Maranui 1968 removed 0.5ha from the tip of the spit overnight.
Season changes in the beach profile occur.

95. Temporal Variations in features and processes at Omaha

97. From the diagrams, describe and explain the temporal variation in the operation of a natural process in the Omaha coastal environment

98. How and why is the environment being modified at the present and is it likely to be changed in the future?
Lesson 10

99. From the field trip
Can you think of any examples of human modification?

100. Human and why the whole environment is being modified, now and in the future
Omaha beach is a natural system, modified by natural processes and by the actions of humans.

101. Human modification of Omaha sandspit
1930’s began farming
sand mining of 380,000m3 from sandbank E of Whangateau Harbour. Caused ebb tide to change direction from S to SE so sand supply to beach ended. Used for Beach Replenishment on Ocean Beach N of southern groyne.
1970 beginning of subdivision and golf course and causeway. Developers bulldozed the fore dunes and built a timber seawall.
Jun/July 1978 storms destroyed seawall and eroded sections.
1979/80 beach protection following major erosion. Because of fear of loss of property.3 Groynes built to trap sand. Quartz dolerite blocks from Flat Top Hill quarry,Wainui,10km W of Orewa and Greywacke from quarry at end of Omaha Valley Rd.were used in the groynes.

102. Groynes 1970 $1.3 million Groynes Natural process modified
Extent of modification
Northern groyne
Built to redirect the ebb tide current to its original southerly direction to increase wave deposition on spit and to prevent sea waves from entering Whangateau Estuary
Successful as wave deposition has increased.
Southern groyne
Built to increase wave deposition and interrupt longshore drift
Successful in increasing wave deposition as shown by high water mark being 34m further out to sea
Swash groyne
Build to decrease wave erosion on the base of the Southern groyne
Successful as wave deposition increased and est accreation was 7000m3

103. What process did the groynes modify?
1 Longshore drift. Draw 3 sketches of 1 before groynes 2 groynes 3 after groynes

104. Human action= building of groynes to modify the process of wave transportation(LSD), resulting in growth of beach to s of southern groyne to 100m
2. 3 groynes built
In southern,
Swash and northern
1. before groynes
3.Sand trapped to s
of s groyne, widening
beach to 100m wide.

105. 2 Dredging of harbour Resulted in Ebb Tide and sand being redirected out to sea and out of the system. Prior to dredging, Ebb Tide and sand flowed south along the spit replenishing the supply.

106. 2 Dredging of harbour 1953-1988 Natural process modification
Removal of sand caused the ebb current to be redirected from S direction to SE direction (depositing sand in bay and forming sandbank outside harbour entrance)
Extent of modification
Extreme as 300m of tip of spit was lost by wave erosion.
Occurred over an extended period of time and did not end when dredging did

107. OTHER Processes modified.
Wind deposition.Dune fences: N end trap sand and build dunes. Cloth has short life-span and fences get buried.
Pedestrian accessways prevent Dune erosion: elevated timber boardwalks and fencing to protect dunes and plants. 20 provided
Harbourside erosion: 1.8km of seawall. Southern 1km around golf course rip-rap and fibrolite, northern section gabion baskets. Need repair over next 5-15yrs.