GEO - Natural Processes (SMCE)

Wave Formation Steps

1. The sun’s radiation warms the sea surface

2. Surface winds blow toward low pressure areas

3. Air and surface of sea interact. Capillary waves form as wind blows over the surface and friction drags the water 

4. Wind waves form and become larger with fetch and duration

The ______ _______ ______ environment is located in the _______ _________, ____ of the equator on the _____ coast of the _____ island of NZ. Approximately __km from ______ _____ with the _______ part of the _____ extending __km

The south Muriwai coastal environment is located in the southern hemisphere 36,50 S of the equator, on the west coast of the North island of NZ. Approx 40km from Auckland City with the southern part of the beach extending 45km

Fetch

Large uninterrupted expanse of sea, 2000km fetch across the Tasman Sea between Australia and NZ’s west coast, the larger the fetch the more energy wind can transfer to water meaning bigger, larger waves

F_____ t______ v_______

Fluid threshold velocity = winds exceed 16km/h 42% of the time

What wind speed does SALTATION occur?

16km/h

Prevailing wind from __ direction, __% of the time

SW wind, 58% of the time

Wave energy?

100,000 joules of wave front

How much sediment is moved ________ by ___ at Muriwai Beach every ______

175,000 m squared moved northwards by long shore drift each year

Saltation STEPS + Percentage

1. When _____ ______ (_m/sec at Muriwai) applied to _____ they begin to _____

2. Grains ______ with other grains, causing _______ into _____

3. _____ grains are ejected at ______ velocity (_m)

4. ______ winds are capable of ______ transporting onto _______, until ____ drops below m/sec or a _____ of _____ _____ ______, dune _______ _____ _____ grains

__%

1. When shear velocity (6m/sec at Muriwai) applied to grains they begin to move

2. Grains collide with other grains, causing ejection into air

3. Fine grains are ejected at greater velocity (1m)

4. Strong winds are capable of rapidly transporting onto foredune, until wind drops below 4m/sec or a zone of zero wind velocity, dune vegetation stem traps grains

75%

PROCESS OF LONGSHORE DIFT

1. ______ energy waves approach from ___ due to _____ of the beach. ______ are generated across ______km _____ across _______ Sea and prevailing wind. Average ____ of __km/h

2. ______ hits the shore, travelling up ________ _________ sediment

3. When ______ runs out of ______, gravity propels ________ _______ back towards the sea, with some sediment ________

4. The next _______ deposits the sediment and once again travels up the foreshore, and _______ again _______ material

5. _________ swash and backwash transports sediment in a ______ motion _________ along the beach. Annually, ___,000 square metres of sediment is _______ Northwards

6. Longshore drift _______ and _______ material on the ______ face for _______ processes of _______ and _______ which results in the ________ of sediment towards ________ where material interacts with __________ growth, leading to _________ of sediment and therefore ______ of __________ shapes due to differences in _______

1. High energy waves approach from WSW due to angle of the beach. Waves are generated across 2000km fetch across Tasman Sea and prevailing SW wind. Average speeds of 16km/h

2. Swash hits the shore, travelling up foreshore depositing sediment

3. When swash runs out of energy gravity propels backwash straight back towards the sea, with some sediment removed

4. The next swash deposits the sediment and once again travels up the foreshore, and backwash again removes material

5. Continual swash and backwash transports sediment in a zigzag motion Northwards along the beach. Annually, 175,000 square metres of sediment is transported Northwards

6. Longshore drift transports and deposits material on the beach face for aeolian processes of deflation and saltation which results in the movement of sediment towards foredunes where material interacts with vegetation growth, leading to deposition of sediment and therefore dunes of different shapes due to differences in vegetation

Types of sediment

Titanomagnetite, silica, feldspar, quartz

Characteristics of TITANOMAGNETITE

black, dense, small (less than 0.25mm), tends to clump, finer grains = difficult percolation = harder to dry

Characteristics of SILICA, FELDSPAR and QUARTZ

lighter colour, larger (1mm - 2.5mm) larger grains = easy percolation = easier to dry

WHY is TITANOMAGNETITE finer?

Older, volcanic, originates from Mt. Taranaki, fluvial/marine processes ground down = finer

Destructive waves

high wave in proportion to length, weak swash, strong backwash = more than 10 crests per minute, more than 1m in height

CONSTRUCTIVE WAVES

In the SMCE, constructive waves form in the _______ due to _______ SW wind ______, which are because of ______ atmospheric air pressure systems (> ____ ) These conditions bring more ____ and ______ weather leading to ___ energy waves, which are _____ than m in height, with ____ than __ _____ per minute. This causes ______ to be stronger than __________ due to less ______ and _______ nature, contributing to a ______ beach.

In the SMCE, constructive waves form in the summer due to reduced SW wind strength, which are because of higher atmospheric air pressure systems (> 1080 mb) These conditions bring more settled and calmer weather leading to low energy waves, which are less than 1m in height, with less than 10 crests per minute. This causes swash to be stronger than backwash due to less energy and spilling nature, contributing to sloping beach.

AEOLIAN EROSION + TRANSPORTATION + DEPOSITION

1. Sediment is supplied to the _____ zone via wave _______ processes e.g ______ drift, placing sediment on ______ face

2. At ____ tide, the sun’s rays _____ sand, _________ moisture, drying it and making it _____ and more susceptible to _______. The ______ the temp the greater rate of _______. E.g average temp in SMCE is degrees, with summers of + meaning ___sediment is susceptible to aeolian erosion, thereby transportation and deposition

3. _______ occurs when wind _______ the fluid _______ velocity (__km/h) Materials are ______ from the _____ part of the beach

4. Aeolian ________ occurs (e.g saltation) as long as winds _______ 16km/h. _______ winds move material via ______ which is when ______ velocity of m/sec is applied to grains (whose _______are at or below the ______ size) and begin to move. As they move, grains ______, causing a _____ reaction towards _________

5. At _______, _________ interacts with onshore winds, _______ them down and creating ____ velocity zones, ________ sediment on dunes, _______ them.

1. Sediment is supplied to the surf zone via wave deposition processes e.g littoral drift, placing sediment on beach face

2. At low tide, the sun’s rays heat sand, evaporating moisture, drying it and making it friable and more susceptible to deflation. The high the temp the greater rate of evaporation. E.g average temp in SMCE is 19 degrees, with summers of 20+ meaning more sediment is susceptible to aeolian erosion, thereby transportation and deposition

3. Deflation occurs when wind surpasses the fluid threshold velocity (16km/h) Materials are removed from the lower part of the beach

4. Aeolian transportation occurs (e.g saltation) as long as winds exceed 16km/h. Onshore winds move material via saltation which is when shear velocity of 6m/sec is applied to grains (whose diameters are at or below the critical size) and begin to move. As they move, grains collide, causing a chain reaction towards foredunes

5. At foredunes, vegetation interacts with onshore winds, slowing them down and creating zero velocity zones, depositing sediment on dunes shaping them.

Vegetation found on dunes

Spinifex, marram, pingao

WHY VEGE NEED SAND

space, water, light = photosynthesis and reproduction, stabilise dunes

MARRAM GRASS

1. Marram grass _____ grow _______ __________ causing ______ dunes 

2. Vegetation _____ down _____ erosion meaning __________ of sediment __________ the plant, leading it to grow _____, further contributing to ____ _____ dunes

3. ______ dunes are ____ susceptible to ________ wave ______ which _____ their shape

1. Marram grass roots grow vertically downwards causing steeper dunes 

2. Vegetation slows down aeolian erosion meaning accumulation of sediment smothering the plant, leading it to grow upward, further contributing to tall steep dunes

3. Steeper dunes are more susceptible to undercutting wave erosion which alters their shape

SPINIFEX

1. Spinifex ____ grow _______ causing ______, _____ dunes

2. When _____ by sediment the plant sends out ______ that grow towards, _____ the _____ of dunes towards the ___, ___________ the ______ slope

3. This shape is _______ to erode as roots _____ sediment together, _______ dunes

1. Spinifex roots grow outwards causing shorter, wider dunes

2. When buried by sediment the plant sends out runners that grow towards, down the front of dunes towards the sea, accentuating the gentler slope

3. This shape is harder to erode as roots bind sediment together, stabilising dunes