Internal Assessment Resource - nzqa.govt.nz · How weathering and erosion produces an observable (current) landform. Examples of a dominant and easily observed landform might be:

Exemplar for internal assessment resource 2.3A Earth and Space Science for Achievement Standard 91189

© Crown 2010

Exemplar for Internal Assessment Resource

Earth and Space Science Level 2

Resource title: Rocks of Banks Peninsula

This exemplar supports assessment against:

Achievement Standard 91189

Investigate geological processes in a New Zealand locality

Expected responses

The moderators have developed expected student responses from a wide variety of sources

Date version published by Ministry of Education

December 2011 To support internal assessment from 2012

[Note: The student work is related to inland Canterbury not Banks Peninsula as the task asks for]

Task Requirements

Students are required to select at least two different rock types found in a selected local area.

For each rock type, produce a concise report, pamphlet or brochure that:

1. Identifies the types of rock selected.

2. Explains the role of plate tectonics in the formation of selected rock types.

3. Explains the role of rock cycle processes in the formation of selected rock types.


© Crown 2010

4. Explains how weathering and/or erosion has shaped the present day observable landforms in the locality.

Notes:

There are two distinct aspects to this assessment task: 1. Geological processes involved in the formation of 2 different rock types 2. How weathering and erosion produces an observable (current) landform. Examples of a dominant and easily observed landform might be: karst limestone, radial drainage patterns, sandstone arches, smooth granite domes, braided river beds, U shaped valleys, steep V shaped gorges, river terraces, wave cut coastal platforms, fault scarps etc. It is assumed that the geological processes of weathering and/or erosion are discussed in relation to the formation of a current landform.

For grade differentiation, holistic judgement of student presentation should be based on comprehensiveness, accuracy and linkage of explanations.

Teachers need to manage authenticity for any assessment from a public source because students have access to assessment schedule and exemplar content. Using this assessment resource without modification may mean that student work is not authentic and invalid.


© Crown 2010

Grade Boundary: Low Excellence

1. Investigate comprehensively geological processes in a New Zealand locality involves:

discussing the link between the plate tectonic processes and the rock cycle processes that have formed the types of rocks in the locality

discussing the link between the erosional processes with the shape of the current landforms in the locality.

What makes this a low excellence:

This report presentation demonstrates a deeper understanding of geological processes (and rock cycle connections) in the formation of rocks and a landform feature in a local area.

It is has extended explanations and some reference to rock cycle processes such as erosion and deposition.

It has relevant illustrative maps, diagrams, equations and photos. Sources are acknowledged.

Typical rock types include: basalt, granite, greywacke, limestone, ignimbrite, sandstone, mudstone, andesite, schist and marble. Note that gravel in a river bed is not a rock type – it is still sediment and not yet made into rock.

To achieve the standard at excellence the student would need to have made the distinction between sediments and sedimentary rocks.

Rock type 1: Formation of Greywacke sandstone

Our youngest Greywacke which makes up the bedrock of the Southern Alps and the North Island,

originates from the erosion and deposition of sediment on deep ocean floors are derived from ancient

Gondwana rocks (now Queensland) some 250mya. Our oldest greywacke formed by similar processes

about 490-443mya and are found today on the West Coast.

Greywacke is a sedimentary rock because it is made from particles of sand and mud (sediment) that

has been eroded from land and then transported by glaciers and rivers to form sea floor fans in

deeper offshore water. The mud fraction is transported further than the sands because they are much

smaller in size and takes less energy to move the particles.

This process of deposition, burial and squeezing occurs on a vast geographic scale. Movement of the

Pacific plate by sea floor spreading as it pushes against continental crust produces folding, faulting

and uplift on a large scale to form mountains. Our local area is only a tiny part of this. Weathering,

erosion, transport and deposition of sediment are key processes in the rock cycle. This is the way in

which materials are recycled.

Rock type 2: Formation of Limestone

Limestone is formed by the deposition of calcium/magnesium carbonate by chemical precipitation out

of sea water and/or the continual settling out of billions of carbonate shelled micro-organisms and

macro shells onto a low energy shallow (but not always warm water) sea floor. Younger limestones

are 23-35 million years old.

An easily observed landform

Limestone is a very common rock in NZ and is responsible for much of our easily observed

landscapes. It is generally easily eroded. These landscapes are formed by the chemical weathering of

calcium carbonate and surface and underground water erosion by the rivers bedload. Rivers carry

large rock particles which erode river banks and river beds. Limestone is often jointed and fractured

and acidic water easily weathers out the joints. This can lead to internal collapse and sinkholes.

Acidified water continuously decomposes the lime. Limestone is a chemical sedimentary rock made

mostly of calcite from shells with various amounts of mud and sand. It is chemical because the lime

comes from once living organisms that secrete a hard shell.

Student 1: Low Excellence


© Crown 2010

Grade Boundary: High Merit

2. Investigate in depth geological processes in a New Zealand locality involves:

explaining the plate tectonic and rock cycle processes that have formed the types of rocks in the locality

explaining the erosional processes that have shaped the current landforms in the locality.

This presentation has explanations for:

(a) How plate tectonics and rock cycle processes operate to produce the two rock types.

and

(b) How weathering and/or erosion produces a current landform. What makes this a High merit:

Explanations clearly link geological processes associated with the rock cycle with formation of selected rock types.

Presentation shows structure. Technical terms have an explanation and are defined. Relevant illustrative diagrams are provided. Key technical words are provided e.g. erosion, weathering, deposition,

sediment, uplift. Relevant diagram provided

To achieve excellence the student would need to have linked all rock types discussed to plate tectonics and their formation.


Greywacke is a very common NZ rock type. Rock types are particular kinds of rock that belong to

either metamorphic, sedimentary or igneous rock groups or classes. Examples of rock types are

basalt and limestone Greywacke is formed form the deposition of muddy fine sand in deep water

The sand and mud is the sediment (unconsolidated loose particles) that has been transported by

rivers and glaciers down to the sea. Particles that are very fine can be transported further out to

sea before they settle onto the sea floor. Greywacke is thought to be muds and sands that flow

down the continental slope and out onto the deep sea floor where they accumulate great

thicknesses. These sediments become deeply buried and undergo change by being compressed.

Greywacke is a grey rock that shows signs of being compressed but not so much that it is

metamorphic.

Greywacke is found nearly everywhere and it makes up the main mountain ranges in both the

North and South Islands. It was originally eroded from the present Queensland coast of

Gondwana. Gondwana is the name of the supercontinent before it broke up 85 million years ago.

Plate tectonics cause continents and ocean floor to move and in the process causes mountains

that are eroded. Erosion is an important geological process of the rock cycle and produces rock

fragments that are transported by rivers. The larger the fragments the faster the river has to go

to carry them along.


Limestone is usually a white or yellowish rock that is made mostly of calcium carbonate. It is a

common rock type and is a type of chemical sedimentary rock. It is called this because all the

materials are either from organic origin or from precipitation out of water. It often has lots of

broken fossil shells in it. Fossils are the preserved remains of ancient organisms.

Limestone forms most often in warm shallow sea where the calcium carbonate precipitates out of

sea water more easily to make the glue that sticks all the shells together. Limestone is able to

form in deeper water, deeper burial and in colder temperatures. The limestone of Punakaiki was

formed about 35 million years ago in warm shallow and coastal waters. Over millions of years

broken shells, sand and mud accumulated on the sea floor and became hardened into limestone

by burial of material on top f it. About 25 million years ago the sea floor was uplifted by Pacific

plate movement and the limestone became exposed to the air.

An observed landform

Because limestone is easily weathered and eroded, it forms many spectacular bluffs and cliffs

that stand out. They make famous tourist attractions like where I live at Punakaiki on the West

Coast. These are called the pancake rocks because of their shape. This was formed by layers of

lime and mud being laid down and the mud is softer and more easily eroded than the limestone

so it erodes more and leaves a surface that is cut in more than the limestone which stands out.

The ocean waves erode the limestone into cliffs. The sea also undercuts the softer rock and these

then collapse leaving blowholes for further erosion.

Student 2: High Merit


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Grade Boundary: Low Merit

3. Investigate in depth geological processes in a New Zealand locality involves:

explaining the plate tectonic and rock cycle processes that have formed the types of rocks in the locality

explaining the erosional processes that have shaped the current landforms in the locality.

This presentation has a full explanation for:

(a) How plate tectonics and rock cycle processes operate to produce one rock type.

and

(b) How weathering and/or erosion explains a current landform What makes this a low merit: It has a clear explanatory link between rock cycle processes, plate tectonics and formation for one rock type and explains effect of erosion on a landform.

To achieve a stronger merit the student would need to give a full explanation for two rock types.


Greywacke is the name given to a very hard type of sandstone. Sandstone is a type of sedimentary

rock which is made from particles (sediment) that have been glued together. In this case, the sand is

mixed with mud and clay and squeezed so that all the water disappears and the particles are pushed

close together. The tiny rock and mineral particle that make up the sandstone have come from the

erosion of land in the ancient past. It is thought the sediment came from the erosion of the ancient

Gondwanaland before it split up to make the continent of Zealandia. The sediment settled onto a deep

sea floor and piled up and up to a thickness of many kilometres. This thickness sank into the crust

only to be uplifted by the movement of the Pacific plate against the Indo-Australian plate. The pacific

plate pushed up the great thickness of Greywacke sediment to eventually make the Southern Alps.

In summary, the formation of greywacke rock is a result of the rock cycle processes of erosion,

transport of eroded material by rivers, deposition onto the sea floor and then pushing up by plate

tectonic movement.


Limestone is made of fossil sea shells stuck together on the sea floor. It is made of calcium. Limestone

is mined for use on farmland so that the acidity of the soil is rebalanced if it is too acid. It is also used

for roadways on dairy farms. Limestone is made when all the lime is compressed together as it gets

buried by other layers of rock.

An observed landform

Mt Hutt is a famous and dominating landform of the Mid Canterbury foothills. IT sticks out onto the

Canterbury Plains and catches all the snow. It has a famous ski field and is high enough to get lots of

snow when the weather is right. Mt Hutt is made of lots of layers (strata)of sedimentary rock which

belongs to what is called the Torlesse Greywacke. This rock is easily eroded and weathered because it

is shattered and jointed due to be being uplifted and folded and faulted s the Pacific Plate pushes

against the Indo-Australian plate. Water is trapped in the joints of the rock and as it freezes, it prises

the joints open so that they can be easily broken, fall down the mountain by gravity and then be

transported by rivers. Mt Hutt is steep and has lots of scree slopes where the shattered rock slides

down hill and into rivers.

Student 3: Low Merit


© Crown 2010

Grade Boundary: High Achieved

4. Investigate geological processes in a New Zealand locality involves:

identifying the types of rock(s) found in the locality describing the plate tectonic and rock cycle processes that have formed the

types of rocks in the locality describing the erosional processes that have shaped the current landforms in

the locality. What makes this a high achieved:

Identified two types of rock(s) found in the locality Described role of plate tectonic in the formation of selected rock types Described rock cycle processes that form the selected rock types Described state or name relevant erosional processes that have shaped an

observable landform in the locality. Describes at least two relevant rock cycle ideas for each selected rock type:

Erosion, transport, deposition, sediment, deep burial, pressure, heating, melting, crystallising.

Descriptions of rock cycle processes are relevant to the rock type.

To achieve merit the student would need to give explanations of rock cycle processes and plate tectonic connections, and the explanation for the selected landform would need to have more detail.


Sediments come from erosion of land and then transported by rivers to the sea. These sediments

become deeply buried heated, and pressured and then uplifted by movement of Pacific Plate

subduction during the Rangitata Orogeny.


Limestone is formed from the accumulation of calcium carbonate shells or precipitated out of

sea water and deposited generally on a shallow sea floor.

Pacific plate movement .influences the depth of water by generating crustal uplift and

consequent sea level changes due to

An observed landform:

Response describes states and/or names relevant weathering and/or erosional processes that

produce the selected landform.

E.g. Limestone caves Limestone is mostly calcium bicarbonate and this is easily weathered away by acid water from rain and underground streams. Underground rivers with their acid water erode and corrode the limestone. Many surface features have a fluted appearance and this is caused by acid water flowing over the rock over thousands of years when exposed to the air. Underground erosion causes rock to collapse and form sinkholes and caverns. Many of these caverns have stalactites’ and stalagmites where water drips and precipitates out calcium bicarbonate.

Student 4: High Achieved


© Crown 2010

Grade Boundary: Low Achieved

5. Investigate geological processes in a New Zealand locality involves: identifying the types of rock(s) found in the locality describing the plate tectonic and rock cycle processes that have formed the


the locality. What makes this a low achieved

Names two rock types and states simply that tectonic plate movement causes up and down movement of the crust.

Has basic presentation showing how each rock type is formed in relation to the rock cycle.

Has descriptive understanding of how erosion produces an observable landform.

To reach a secure achievement the student would need to give more detail in their description of the rock types and their formation.

Rock type 1: Greywacke

This rock is one of the most common rocks found in NZ and makes up the main mountain chains

in both Islands. Greywacke is named because of its drab grey colour. It is a very hard sandstone

and forms huge thicknesses of sediment that have been uplifted by plate tectonics. Sandstone is

made from broken rock fragments that have been eroded and transported and eventually

dumped out at sea. Greywacke is made when all the sand is compressed by being buried deeply

in the Earth’s crust. Moving tectonic plates causes the pile of sediments to be pushed up and in

some cases to be pulled down.

Rock type 2: Limestone:

Limestone is made of shells and forms in shallow warm water. So, when the limestone was

made, the sea must have covered the land and as animals died their shells built up on the sea

floor. Limestone is made of calcium carbonate and is usually white or yellow in colour.

Sometimes it has sharks teeth in it and sometimes whole shells. The lime is made into limestone

when it becomes buried and compressed. Because the giant tectonic plates are constantly

moving, they sometimes cause the land to go up and down. As the land goes down, the sea is

able to cover the former land and deposits of lime can be formed.

Erosion and landforms.

When acid eats away limestone rock, it forms caves and caverns. Often the caves form because

they are eaten away from beneath and the bottom falls out. Sometimes the top is eaten away

and the ground sinks to be seen as sinkholes. These can be dangerous. In our local area, there

are many sinkholes and they often have underground streams in them that also erode the rock

away and carry the pieces down to the sea. These sinkholes often collapse above the direction of

flow of underground streams.

Student 5: Low Achieved


© Crown 2010

Grade Boundary: High Not Achieved

6. Investigate geological processes in a New Zealand locality involves: identifying the types of rock(s) found in the locality describing the plate tectonic and rock cycle processes that have formed the


the locality. What makes this a high not achieved:

Has an inadequate description of rock cycle processes. Has an inadequate description of weathering/erosional factors in formation of

an observable landform. Does not identify (name) two rock types.

To meet achievement the student would need to have described the two key rock types in their area and described an observable feature.

Rock type 1. Greywacke.

Greywacke is the name given to a type of sedimentary rock that is found all over NZ. It is grey in

colour and is made of rock particles. In our local area of Mt Cook there are many different layers

of greywacke rock which have lots of big folds in them. These folds were caused by plate

tectonics.

Erosion and landforms

Around Kaikoura there are lots of caves. These caves are found in limestone and have been

made by the action of the sea crashing against the rocks. Some caves are quite high up

suggesting that the coastline was once higher than it is today.

Student 6: High Not Achieved

Documents

Internal Assessment Resource - nzqa.govt.nz · How weathering and erosion produces an observable (current) landform. Examples of a dominant and easily observed landform might be: