Geomorphology is the study of changing landforms. Landforms are always changing,

sometimes quickly and sometimes slowly. Some processes build landforms up while

others modify them as can be seen in the diagram on screen. The Earth's landforms

are built up by the processes of volcanism, folding and faulting. Folding is where

crustal plates move together forcing rocks between them to fold as

can be seen at the diagram below. The mountain ranges formed are the most common type.

Much of the hill country in the North Island of New Zealand is the result of

folding, such as the Kaimanawa ranges which have buckled due to the coming

together of the Pacific and Indo-Australian plates. Faulting occurs where

there is a crack in the Earth's crust known as a fault. Most movement of land

by these faults are slow, but a sudden movement can result in an earthquake.

Depending on the direction of movement, land can move in an upwards, downwards or

sideways direction. For example, the Southern Alps of New Zealand have been

formed by uplift of land alongside the Alpine Fault. Volcanism is where cracks

in the Earth's crust allows magma to reach the surface for a volcanic

eruption, where cools and hardens to become a volcano. For example these

mountains in the Tongariro National Park which is located in the central North

Island of New Zealand.

Land is then modified by various erosion processes.

The removal of soil and rock is called weathering.

The transportation of the material is usually down-slope due to gravity,

and the deposition of material results in deposition landforms.

Some of these natural processes include the actions of wind, rivers, glaciers, waves

and the freezing and falling of ice.

Erosion by wind is known as Aeolian erosion. This type of erosion is significant in

environments where the soil is unconsolidated such as beaches and deserts.

Wind transports the fine particles and deposit them as dunes.

Erosion by rivers is called fluvial erosion.

Streams and rivers erode rocks and soil from riverbeds and banks

and typically deposits the material downstream on the floodplains of river valleys, or in deltas.

The clay, silt, sand and gravel deposited by flowing streams is known as alluvium.

Glaciers are rivers of ice.

They erode by grinding rocks and transport enormous quantities of debris as they move down-slope.

They carve out U-shaped valleys such as these examples in Fiordland.

Material deposited at the side and terminus of the glacier are called moraines.

Erosion by the freezing and thawing of water is known as periglacial erosion.

This is significant in alpine regions where water gets into the cracks in rocks.

The daily or seasonal freezing and thawing can cause the rocks to shatter.

Ocean waves are an agent of coastal erosion.

Through processes like abrasion, hydraulic action and corrosion,

waves break down rocks into finer sediments like sand

and transport the material along beaches.

Deposition features that result from the transportation of sediment include beaches,

spits, bars, tombolos and mud flats.

Wave erosion leaves behind features such as cliffs, wave cut platforms, caves, arches and stacks.

Mass movement also known as mass wasting

is when large quantities of soil and rock move down-slope by the force of gravity.

Sometimes this process can happen slowly as in the process of soil creep.

Other times it can be quick when there is a landslide, a lahar or an avalanche.

Factors that can increase the potential for mass wasting include an increase of water content in the soil,

a reduction in the vegetation that holds the soil together,

the undercutting of the slope by either erosion or excavation,

and by earthquakes.