Explain how the processes of weathering, erosion, transportation and deposition

have shaped New Zealand

New Zealand has been influenced by many processes which have given the country

its particular shape. Starting from the everyday coastal erosion, to the very

common rivers of New Zealand, they have shaped our landscape in a dramatic

difference. Great forces like waves from the sea, glaciers and rivers have created

the New Zealand landscape and continue to shape it today. They also have shaped

us economically through these four processes. These forces all have the processes

of weathering, erosion, transportation and deposition.

Erosion, is the carrying away of rocks and soil by wind, water and gravity, that

have been worn down. Coastal erosion was the great influence that has shaped New

Zealand. Coastal erosion is the process of the sea eroding rock. This can be

divided into three parts: hydraulic action, abrasive and chemical. Hydraulic action is

when massive amount of sea water and air gets forced into cracks of the rock

causing eventual erosion.

This is a photo of Pancake Rocks,

Punakaiki, Paparoa National Park,

West Coast, South Island. This is an

example of coastal erosion. The

waves eroded the weaker part of

the rock first which then became

separated from the bigger part of

the rock. These rocks are 3 the left-

over of a big rock which its soft part

had been eroded away. Abrasive is when small particles of rock and sand floating

in the sea, crashes onto the rocks causing erosion. Chemical is acid rain eating

away the rocks and salt particles in the sea eroding the rock.

This is photo of Hole in the Rock of Bay

of Islands. This is an example of coastal

erosion. The wave has found the easiest

way to wear and break down the rock

and eventually turned it into a hole. This

is called weathering. Weathering is the

process of rock being constantly worn

away and broken down. Weathering can

be divided into two thing; chemical and physical. Chemical weathering happens

when chemicals, suck as acid in rain water, gradually dissolve and eat away at

rocks.

For example, limestone rock dissolved by rain

water is responsible for many caves and

gorges in New Zealand. This includes the cave

in the Castle Hill basin, Canterbury, which has

been formed by rain water dissolving

limestone.

Physical weathering makes rocks break

away apart in sheets, blocks or grains. It can be divided into three categories;

exfoliation, freeze-thaw action and biological. Exfoliation: Rocks warmed by the

sun expand and when they cool down at night they shrink. The outer layer of the

rock expands more, because it is directly exposed to the sun’s heat. Eventually it

separates from the rock and peels off. Freeze-thaw action: Water seeps into

cracks in rock and then freezes and expands. As the temperature rises and falls, the

crack gradually grows until the rock breaks apart. Biological weathering is when

bacteria, lichens and mosses eat away at the rock surface by producing chemical.

Animals burrowing and roots growing in the ground is also biological weathering.

Hole in the Rock may be an example of biological weathering. The mosses that are

growing on the rocks cause it to have cracks by producing chemicals.

Another powerful factor that has shaped New Zealand the most is the glaciers. New

Zealand’s landscape (especially south island) has been mostly shaped by glaciers.

This is a photo of Fox glacier of the

south island. It has carved out a

valley of its own with the typical U-

shape of glacial valley. The bottom

part of the glacier is mostly grey

and black, caused by the glacial

erosion which has the sand-paper

effect. When glacier moves, it

carves out the soil and rock which

is called abrasion, and carries with it down the valley. This is called transportation.

After the glacier carried the sand and rocks onto the bottom of the valley, it dumps

the rocks leaving a pile of erratic which is the term for left-over rocks from glacial

erosion. Dumping or depositing a pile of sand or rock by transportation is called

deposition.

This is a photo of Aoraki valley,

South Island. This is another

example of glacial erosion. The

valley has been worn and carved

away by a glacier. Now the valley

has the typical U-shape of glacial

valley. The middle empty part is

where the glacier had once been;

which is a plain.

The plain made by the glacier, have

shaped us not only in a geological way but in economical and social way. By carving

out the valley and making a plain, train track may be built and even some houses

can be built. This train track may effect on us if this track was used for trading.

Manhattan, United States, is an example of how the glaciers shaped the city

economically and socially. Long ago in Manhattan, United States, there was glacial

erosion. This had a massive effect on where the tall skyscrapers and tiny small

ordinary building should be placed.

This is a photo

of Manhattan. If

you observe

closely, there is

a curve above

the city. The

curve starts on

the low left hand-side but gets higher in the middle and lowers again at the right

hand-side of the photo. This is caused by the glacial erosion. The glacier carved the

soil out and deposited the hard rocky part in the middle. Therefore tall skyscrapers

that needed strong foundation could stand safely on the eroded rocks and soil. On

the other hand, the soft and weak soil was deposited on the right and left hand-side

of the photo. This caused only small and tiny buildings which did not need strong

foundation to be built on it.

The most obvious but very influential factor is river. Rivers are the best example of

weathering, erosion, transportation and deposition.

This is a photo of Hooker

valley, South Island

which is a glacial valley.

In the middle, there is a

river. The river started

off from the mountains

behind and travelled

through the valley made

long ago by a glacier.

This river has weathered

the rocks from the

mountains and the rocks that were in the valley. Then the river transports the rocks

and it deposits the dirt and soil onto the slower part of the river which is the inner

part of the river. This creates the sand bank.

This is a photo of the Grey River near

Greymouth, West Coast, South Island.

The same effect occurs in this river too.

The river deposits the transported soil

and dirt onto the slower and inner part

of the river. This is the white sand bank.

The white sand is the weathered rock

from the mountains that have been

eroded and transported until it became sand and reached the Grey River.

Therefore, it is very clear that the four processes of weathering, erosion,

transportation and deposition have shaped New Zealand and are linked together.

The three massive forces of shaping the New Zealand landscape have definitely

shaped us through the four processes. They always follow another and do not

happen independently. They have shaped us not only in geological way but in

economical way as well. These four have, are and will keep shaping the landscape

of New Zealand.