MODULE mod7A mod7B mod7C mod7D mod7E mod7F mod7G mod7H mod7I mod7J mod7K mod7L mod8A mod8B mod8C mod8D mod8E mod8F mod8G mod8H mod8I mod8J mod8K mod8L mod9A mod9B mod9C mod9D mod9E mod9F mod9G mod9H mod9I mod9J mod9K mod9L 8ha1
8Ha1 Sandstone - squashed sand?
Name _____________________________ Class ____________
We can look at the way sedimentary rocks are formed by squeezing some damp sand.
Method
1 Pick up a small amount of damp sand in your hand.
2 Squeeze your fingers tightly around the sand. Watch carefully what happens.
3 Open your hand and look at the sand again.
Recording your results
Write down what the sand looked like, or what happened, in each of the steps in the method.
Step 1: _________________________________________________________________________
_______________________________________________________________________________
Step 2: _________________________________________________________________________
Step 3: _________________________________________________________________________
Considering your results/conclusions
Complete these sentences using the words from the box.
Squeezing the_________________ sand forces out the _________________ . This helps to make
the _________________ of sand _________________ together. The _________________ sand is
much _________________ than it was before it was squashed. This is because the grains of
_________________ are much _________________ together.
closer damp grains sand smaller squashed stick water
[ observing, considering ]
8Ha2 Sedimentary rocks 1
Name ____________________________ Class ____________
Apparatus
- Hand lens or microscope - Sedimentary rock samples
Sedimentary rocks are formed when layers of sediment are compacted (squashed) and cemented (glued) together. As they are all formed in the same way, we might expect them to have similar properties.
You are going to examine and test different sedimentary rocks to find out what features they have in common.
Name of sedimentary rock
Colour
Texture
Grains obvious/ grains not obvious
Fossils/no fossils
From my observations, I can see that sedimentary rocks have these features in common:
a ______________________________________________________________________________________________________________
b ______________________________________________________________________________________________________________
c ______________________________________________________________________________________________________________
8Ha3 Glue and sand grains
You are going to try to see how the grains of sand are held together in a pile of damp sand and in sandstone. After this, you will use a model to see what needs to happen to turn sediment into sedimentary rock.
Experiment 1: Observing sand and sandstone
1 Look at some damp sand with a hand lens. Pay particular attention to how the grains are being held together.
2 Look at some sandstone in the same way.
- Damp sand
- Sandstone
- Hand lens
1 Draw a picture of what you saw when you examined damp sand.
2 Draw a picture of what you saw when you examined sandstone.
3 From your observations, write down how you think the grains are held together in:
a damp sand b sandstone.
Experiment 2: Models of sedimentary rock
- Large plastic syringe (without end)
- Sand
- Water
- Clay suspension
- Plaster of Paris
- Petri dish
- Disposable plastic cups and spoons
1 Place some sand in a plastic cup and add some water so that the sand is very damp, but not dripping wet.
2 Place some damp sand into the syringe so that it is about two-thirds full.
3 Place the syringe open end down onto a plastic Petri dish and push downwards, while also pushing the plunger into the syringe.
4 The pressure of pushing the plunger into the syringe should compress the sand. Now lift the syringe up slightly and push the plunger in further until the pellet of sand is sitting in the Petri dish.
5 Repeat these steps using a mixture of sand and clay suspension and then sand and plaster of Paris solution.
6 Leave the pellets to dry then examine them carefully with a hand lens.
4 Record your observations in a table like this:
Pellet made from
Appearance of grains
Other observations
damp sand
damp sand and clay suspension
damp sand and plaster of Paris solution
5 How is the pellet made of damp sand different to the sand you started with?
6 Is there any difference between the pellets you have made? If so, what?
7 a Sand grains are large and do not fit together well. When you made the second pellet with sand and clay, you could squash the clay and sand grains together. What do you think happened to the small clay grains to allow you to do this?
b Where did the plaster of Paris go when you made the third pellet?
8 What does this experiment tell you about the formation of sedimentary rocks?
8Ha4 Layers of sediment 1
Sedimentary rocks are formed from layers of sediment. The layers of sediment can be laid down over a very long period of time. If the type of sediment which is deposited changes, then the type of rock which is formed will also change. If different layers of rock are formed on top of one another, we get layers of rock like those shown in the cliff face.
Imagine that the area where you are sitting was once covered by water. This is what might have happened to make the sedimentary rocks beneath you.
- The first layer of sediment to be deposited was gravel, made up of fragments of other rocks.
- Over a period of time, smaller rock fragments were deposited next, forming a layer of sand.
- Shellfish lived in the water and as these died, their remains formed a layer of sediment.
- The sea level dropped and the water became much
Layers of different sediments form different rocks:
- gravel forms conglomerate
- sand forms sandstone
- clay forms shale
- plant fragments form coal
- remains of small shellfish form shelly limestone
- microscopic plankton form chalk.
shallower and a layer of very small clay particles was deposited.
- Trees and plants grew along the edge of the water. When the trees died their remains formed a layer of sediment.
- There was a change in sea level and the shallow marshy area became flooded. Microscopic organisms called plankton lived in the warm waters. As they died, their remains formed another layer of sediment.
1 Symbols can be used to represent these rocks. Cut out the symbols below and stick them in the order in which they were formed in the passage above. Remember to put the rock formed from the first layer of sediment at the bottom.
2 Which rock was formed first?
3 Which rock was formed last?
4 Which rock will be squashed the most? Explain your answer.
[ knowledge ]
8Ha5 Sedimentary rocks 2
This picture shows layers of sedimentary rocks in a cliff face. Each rock layer has been drawn using a different symbol for each type of rock.
1 Fill in the gaps using words from the box. You may need to use some words more than once.
Over a _________________ period of time, layers of _________________ collect on top of
each other. The newer layers on top _________________ the layers of sediment below them.
This forces the _________________ closer together. The water gets squeezed out from
between the _________________ and they get 'glued' together by chemicals that had been
_________________ in the _________________ . Sedimentary _________________ is
formed.
Some sedimentary rocks are made from small grains such as _________________ .
Others, like conglomerate, are made from _________________ grains such as gravel or stones.
dissolved grains large long sand sediment squash rock water
2 This key shows what symbols are used to show different types of rocks.
Look at the diagram on the first page.
What sort of rock forms:
a the oldest layer
___________________________________
b the youngest layer
c the greatest number of layers
d the most common type of rock in the cliff face?
3 A sandy sea bed was covered by a thick layer of sea shells from dead sea creatures. This layer of shells was covered by a layer of clay from a huge landslide. Gravel and some large boulders then covered this layer. Over millions of years all these layers were turned into rock.
Fill in the diagram below with correct symbols for each rock layer.
4 Why do you think scientists often show different types of rock with symbols rather than just
drawing what the rock looks like? _______________________________________________
__________________________________________________________________________
[ knowledge, literacy ]
8Ha6 Layers of sediment 2
Sedimentary rocks are formed from layers of sediment. These layers of sediment can be laid down over a very long period of time. If the type of sediment which is deposited changes, then the type of rock which is formed will also change. If different layers of rock are formed on top of one another, we get rock strata (layers) like those shown in the cliff face.
Imagine that the area where you are sitting was once covered by a sea. Water from a river was flowing quite quickly into the sea, and the first layer of sediment to be deposited was
Symbols can be used to represent rocks:
gravel, made up of fragments of other rocks. Over a period of time, the river water slowed down, and smaller rock fragments were deposited, forming a layer of sand. Shellfish lived in the water, and their shells formed a layer of sediment when they died. The sea level dropped and the water became much shallower and deposited a layer of very small clay particles. Trees and plants grew along the edge of the shallow water and as these died they fell into the water. Over a long period of time they formed a layer of sediment. There was a change in sea level and the shallow marshy area became flooded. Microscopic organisms called plankton lived in the warm waters. As they died, their remains formed another layer of sediment.
1 Draw out the layers of rock formed, as described in the passage above. Use the symbols above.
2 Why do you think scientists often show different types of rock with symbols rather than just drawing what the rock looks like?
3 Which layer of rock will be under the most pressure? Explain your answer.
4 What are layers of rock properly called?
5 Some limestone is not composed of many bits of shell. Draw out a symbol that could be used to represent this type of limestone.
6 a What does the word 'deposited' mean?
b Explain why the river no longer deposited gravel when it had slowed down.
7 When sand is squashed (compacted) by layers of sediment above it, the grains are pushed together.
a What happens to the water between the grains?
b How do the grains become 'glued' together to form sandstone?
c What is the proper term for this 'gluing together'?
8Ha7 Layers of sediment 3
Layers of sediment are formed when rivers and streams deposit the rock fragments they are carrying. This can happen when the river begins to flow more slowly. But it is not the only way in which a layer of sediment can be formed.
Your task is to find out about the different types of sedimentary layer and how they are formed.
You may find it helpful to look up the following key words:
marine eolian streams/rivers fossils
When you have done your research, your task is to set up a 'Rocks Roadshow' to explain to the public how different sedimentary rocks are formed.
[ research ]
8Hb1 How much carbonate?
Preliminary experiment
In these experiments you will try to find out how much carbonate there is in different limestones.
- Watch glasses - Crushed limestone (calcium carbonate)
- Pipettes - Dilute hydrochloric acid
- Eye protection - Limestone samples to test
Wear eye protection.
1 Place a level spatula of crushed limestone on the watch glass.
2 Add some dilute acid, one drop at a time.
1 Write down what happened to the rock when acid was added.
2 Write down why you think you got these results. Try to explain what was happening to the rock.
Planning
3 Now plan an investigation to compare the amount of carbonate in two samples of limestone.
- How will you make sure you conduct a fair test of the two samples?
- What will you keep the same?
- What will you change?
- How will you know which sample of rock contains the most carbonate?
- What will you record?
- How will you make sure your investigation is safe?
4 Show your plan to your teacher before you start.
[ planning, observing, considering ]
8Hb2 Limestone gridword
This is a slightly more difficult type of puzzle!
1 Write your answer to the clues on the lines.
2 Using a pencil put the words into the grid. You will notice that there are no numbers for the clues or on the grid. You have to get the words to all fit into the grid!
All rocks are made of these chemicals. ___________________________________________
Limestones react with these chemicals to produce carbon dioxide. ______________________
Many limestones are formed from these. They are the things that many small sea creatures
live inside. ______________________________
Most limestones are basically this colour (although some contain other minerals which make
them different colours). ______________________________
The first word of this chemical compound is 'calcium'. It is the chemical found in all
limestones. ______________________________
These are the remains of dead plants and animals that have got buried in a layer of rock grains
and turned into rock. ______________________________
This is a type of limestone which used to be very common in school classrooms.
This is a type of sedimentary rock. ______________________________
This is a word which refers to any rock that has been formed from layers of grains which have
been deposited and then squashed. ______________________________
This is the name given to the particles that make up a rock. They can be rounded or
interlocking. ______________________________
8Hb3 Types of limestone 1
The composition of sedimentary rocks varies and depends on the way they were formed. There are different types of limestone - chalk is formed from the shells of microscopic animals, coquina is formed from larger shell fragments and oolite is formed from sediments of calcium carbonate deposited when sea water evaporated.
All sedimentary rocks can be formed wherever sediment is deposited. Sediments can be deposited on land or at sea. On land, sediments can be deposited on the beds of glaciers (boulders), rivers and streams (gravels and sands) and during periods of flooding (fine sand and silt). They can be deposited on the beds of lakes (fine sediments), in swamps (coal), or in deserts (sand). Sediments are often deposited where the land meets the sea, at beaches, estuaries, and in lagoons (areas of quieter water, protected from the power of the waves). At sea, sediments can be deposited on the sea bed and around reefs. As sea water evaporates, some of the mineral salts dissolved in it form solid particles of sediment. This is called precipitation. For example the limestone, oolite, can be formed from dried up tropical seas and lagoons.
1 a Make a list of all the different places where sediments can be deposited.
b Chalk is pure white and formed from the shells of microscopic sea animals. Which of these places would have been suitable for the production of chalk? Explain your answer.
c Coquina is a limestone formed from larger fragments of sea shells. Where would you expect to find coquina? Explain your answer.
d Some samples of limestone contain more impurities, such as iron compounds, than others. Which of these places would be most likely to contain impurities such as iron compounds? Explain your answer.
2 a When sedimentary rocks are formed the grains become 'squashed' together. Explain why this happens.
b What is the proper term for this 'squashing together'?
c The grains of sediment become 'glued together'. What is the proper term for this gluing together?
8Hb4 Types of limestone 2
There are several types of limestone, each of which has a different composition and has been formed in a slightly different way.
1 Use the table of information below to draw general conclusions about the composition and colour of a piece of limestone and:
a where it was formed
b how it was formed.
2 Use your conclusions to predict the composition of a piece of limestone which was formed in a cave as rainwater dripped from the ceiling and evaporated, forming a stalactite.
Name of limestone
Chemical composition
Type of sediment
Conditions and place of formation
Notes
Oolitic limestone
Up to 85% calcium carbonate (calcite) but may also contain dolomite, haematite and silica grains.
Formed when calcite is precipitated around a central grain such as a small fragment of shell or a grain of quartz.
Sediment formed in warm, shallow tropical seas and lagoons.
Precipitation of calcite is caused by high salt content of the sea and/or evaporation of water.
Range of colours from white through yellow to brown and red, depending on the impurities present.
Travertine
Up to 95% calcium carbonate, in the form of the mineral calcite.
Formed when calcite is precipitated in layers.
Sediment is deposited as crystals formed when water from rivers or hot or cold springs evaporates.
A whitish, crystalline form of calcium carbonate. A more porous form of travertine is known as tufa.
Chalk
Up to 99% calcium carbonate, in the form of the mineral calcite.
Formed from the shells and skeletons of microscopic sea animals.
Sediment formed in large areas of shallow sea water which were usually free from other sediments.
A very pure, fine-grained white variety of limestone. Chalk is also soft and porous. A type of fossiliferous limestone.
Coquina
Up to 95% calcium carbonate.
Formed from larger fragments of sea shells and coral.
Sediment formed on the sea bed in shallow water. It is composed almost entirely of fossil shells cemented together by calcite (calcium carbonate).
The shells may be the size of pieces of gravel and are usually broken into pieces of a similar size. A type of fossiliferous limestone.
Fossiliferous limestone
Up to 85% calcium carbonate, depending upon the impurities present.
Formed from a large number of fossils held together by a calcite cement.
Sediment is usually formed on the sea bed in shallow water.
Colour and texture depend upon the number and type of fossils contained in the rock.
Dolomitic limestone
50-60% calcium carbonate (calcite), the rest being calcium magnesium carbonate (dolomite).
Formed by the replacement of calcium carbonate with magnesium carbonate from sea water.
The original limestone sediment is changed over a period of time by the presence of magnesium salts in high concentration in sea water.
This rock is less reactive with hydrochloric acid than the other types of limestone. The texture of the original limestone is usually conserved.
8Hb5 Information from limestone
The composition of sedimentary rocks varies and is determined by the way in which they were formed. All samples of limestone contain the mineral calcite (calcium carbonate). Most limestones were formed from sediments deposited on the sea bed (and most contain the remains of animal shells), though some are formed in lakes, rivers and on land. The composition of a particular piece of limestone can provide geological information about the position of the sea bed at the time the sediment was being formed. Some reef-like and shell limestones contain the mineralised remains of corals, clams and oysters. As these organisms are all still alive on Earth today, we can identify the conditions in which they are likely to have lived - shallow, mud-free lagoons and reefs.
Oolitic limestone is formed when water evaporates and the soluble compound calcite is precipitated. Evaporation is greatest from large expanses of warm water. The presence of oolitic limestone suggests a tropical sea or lagoon environment.
The calcite in limestone is often accompanied by other minerals, such as dolomite and aragonite. These minerals are also carbonates and all three minerals are colourless or white. Most limestones are lightly coloured due to the presence of impurities in the rock. These impurities may include sand, clay, iron compounds or the remains of plants and animals. Fossil remains in a piece of limestone can also provide biological evidence about the species living at the time that the sediment was deposited.
1 Describe the two processes by which sediments containing calcium carbonate can be formed.
2 How can the composition of a piece of limestone help us to understand the history of the Earth?
3 Chalk is a limestone formed from the shells of microscopic animals. It is pure white in colour. What can you conclude about the water in which these animals lived?
4 A small amount of limestone is formed from calcium carbonate deposited on land. How and where do you think this might happen? (Hint: Would this process involve the deposition of shells or the precipitation of calcium carbonate?)
5 Dolomite is calcium magnesium carbonate (CaMg(CO3)2). Calcium carbonate fizzes when a weak acid is added to it. Predict what you think will happen if weak acid is added to some dolomite. Explain your answer.
6 Choose one of the rocks named above and describe how it was formed in as much detail as you can.
8Hc1 Pairs of rocks 1
Examine as many of the marked pairs of rocks as you can.
Complete a new card for each pair of rocks.
Name of rock
Type of rock
Appearance
Hardness
How much water it soaks up (porosity)
Does it have obvious crystals?
These two rocks are similar because they both:
They are different because:
8Hc2 Pairs of rocks 2
Your task is to examine and test pairs of rocks as carefully as you can, so that you can identify the similarities and differences between each rock within the pair.
The rocks are in matching pairs - a metamorphic rock is paired with the rock from which it was made when metamorphism happened. For example, marble (metamorphic rock) is paired with limestone (sedimentary). Examine and test as many pairs of rocks as you can and then try to answer the following questions.
1 From your results, how are metamorphic rocks similar to sedimentary rocks? What properties are the same?
2 From your results, how are metamorphic rocks different from sedimentary rocks? What properties are different?
3 Imagine that you have been given a rock which is unlabelled. How would you find out what type of rock it is? What clues would you look for?
4 Write a list of questions you might ask about a rock which would help you to tell if it was a metamorphic rock or not.
8Hc3 Metamorphic rocks
1 Complete the gaps in these sentences using words from the box below. You may need some words more than once.
All rocks are made up of different __________________ . When these minerals are
__________________ and squashed, they can change into __________________ ones.
Metamorphic rocks have been __________________ within the Earth.
All __________________ rocks were originally other types of rock. As more layers of rocks
build up, the older rocks get pushed __________________ into the Earth. Earth
__________________can squeeze the rocks and raise their __________________ . Gradually,
over a very __________________ period of time, the rocks get changed into
__________________ rocks. One example is the __________________ rock limestone,
which changes into __________________ when it is heated and squashed.
changed different down heated long
marble metamorphic minerals movements
sedimentary temperature
2 This table shows the names of sedimentary rocks, and the names of the metamorphic rocks they turn into. Use words from the box below to complete the table.
Name of original rock
Name of metamorphic rock
marble
limestone quartzite sandstone shale slate
8Hc4 Diamonds are forever
Diamond is a particularly hard form of one element, carbon. Diamond is made of the same element as soot and graphite. Diamonds are very rare and are only found in a few places in the world. They are the hardest mineral known. They are also very beautiful when they have been cut and polished - the surfaces reflect light, forming rainbow spectrum effects. They are formed when pure carbon crystallises deep within the Earth, where pressures are extreme and temperatures are very high. Recently, a process has been designed which enables chemists to make 'industrial' diamonds - diamonds formed from pure carbon in the laboratory. These have the same properties as natural diamonds but are much cheaper. These industrial diamonds can be used for any job which needs a material that is very hard and that will last for a long time. One example is as the cutting surface on a drilling machine. The drilling machine that cut the Channel Tunnel used diamond drill bits.
1 What element are diamonds made from?
2 How are diamonds formed in the Earth?
3 If diamonds are only made of the element carbon, are they a rock or a mineral?
4 Diamonds have very special properties. List as many properties of diamonds as you can.
5 Why do you think chemists needed to make 'industrial diamonds'?
[ literacy, knowledge ]
8Hc5 Slate
Slate is a material often used for making the roof tiles for buildings. It can be used for this purpose because the rock can be split into very thin sheets. This is a skilled job which is carried out by craftsmen who call the process 'dressing the stone'. It is very easy to break slate if it is cut the wrong way.
Slate was formed by great pressure on layers of shale. The pressure caused the grains in the shale, a sedimentary rock, to form into new layers. It is these layers which enable the craftsman to split the stone quite easily. They also give slate different properties, depending upon the way it is cut. If the slate is split along the grain of the stone, the pieces of rock will be quite strong and very weatherproof.
If the stone is cut across the grain, the rock is much weaker and more likely to break. It is also less weather-resistant and may let water leak in.
Cutting slate carefully along the grain.
A roof slate.
The layers in a block of slate.
1 Why is it difficult to cut slates of the right size?
2 Slate quarries are always surrounded by mounds of broken pieces of slate (called slate spoil). Where do you think these came from? Why is there so much?
3 Roofing slates last for many years but are very expensive. Why do you think this is?
4 Modern roofs often have tiles made from concrete. These are man-made and coloured. Why do you think builders use these tiles instead of real slates?
5 The layers within the rock allow us to use slates for roofing. Where did these layers come from? How were they formed?
6 Slate is also used to build the walls of houses in Wales and some other parts of Britain. If you were going to build a wall out of slate blocks, which way round would you place the layers? Draw a diagram to help you explain your answer.
8Hd1 Investigating crystal size 1
Complete the gaps in the following sentences using the words from the box. You may need to use some words more than once.
cooled crystals fridge hot salol
Rock is very difficult to melt, so I used some____________ instead. This melts easily and can be
____________ down so that it makes ____________ in the laboratory.
I took some of the ____________ liquid and let it cool down slowly on a warm watch glass. I also
put some of the ____________ liquid in a ____________ so that it would cool down quickly.
Draw what each of the crystals looked like after they had cooled.
Cooled slowly.
Cooled quickly.
Considering your results/conclusion
From my results I can see that the crystals which are made when the chemical cools quickly are
______________ (smaller/bigger) than the crystals made when it cools slowly. Slow cooling makes
______________ (big/little) crystals; quick cooling makes ______________ (big/little) crystals.
Imagine you are being interviewed about this experiment on TV. Complete the interview using information from your experiments.
Scientists have made a major break-through in their understanding of the structure of the Earth. Careful observation and recording of data has enabled a leading team of scientists to describe how granite was formed and why different pieces of granite have different sized crystals in them. We interviewed one of the scientists who said …
'Granite, an ______________ (igneous/sedimentary) rock, is made when molten rock cools down.
Different pieces of rock have different sized crystals in them. I think that the ______________
(big/little) crystals were made when the molten rock cooled down ______________
(slowly/quickly) and that the ______________ (little/big) crystals have been made when the molten
rock cooled down more ______________ (slowly/quickly).'
8Hd2 Investigating crystal size 2
You are going to be interviewed on TV about the formation of crystals in igneous rocks and how they are affected by temperature. You need to plan an experiment to demonstrate this as part of your interview.
1 How will you do this demonstration? You will need to think about the following.
- What chemical you will use. You will not be able to use molten rock in a TV studio.
- How you will allow the chemical to cool.
- How you will carry out a fair test.
- What apparatus you will need.
- What observations you are going to make.
- How you will stay safe while doing your demonstration.
Show your plan to your teacher before you do any practical work.
2 Carry out your demonstration to make sure it works.
3 Complete the interview below, describing your demonstration to show why crystal sizes in igneous rocks vary. Briefly state your results and explain how these led you to reach your conclusions.
8Hd3 Density of igneous rock
You are going to compare the densities of some igneous rocks. The density of a material is the mass (in grams) of one cubic centimetre (1 cm3) of that material.
density (g/cm3) = mass (g) / volume (cm3)
- Samples of granite and gabbro
- Large plastic measuring cylinder (or displacement can and large bowl)
- Accurate top pan balance
Different rocks contain different minerals, some of which are more dense than others. Granite and gabbro are igneous rocks which have different densities.
Experiment 1: Finding the density of granite and gabbro
1 Select a dry piece of granite and use a top pan balance to find its mass in grams. Draw a results table like the one below and record the mass.
2 Place 100 cm3 of water in a large plastic measuring cylinder. Record the volume of water in your results table.
3 Carefully place your piece of granite into the water in the measuring cylinder. Record the new volume in your table.
4 Calculate the volume of the piece of granite (Hint: The volume of the piece of granite will be the increase in volume shown on the measuring cylinder). Record the volume of the granite in your table.
5 Calculate the density of the granite and write it in your table.
6 Repeat steps 1 to 5 using a piece of gabbro.
1 Which rock has the highest density: granite or gabbro?
2 Both of these rocks are igneous rocks. Why do they have different densities?
Experiment 2: Finding the densities of basalt and obsidian
Repeat the method above to find the densities of basalt and obsidian. Record your results in your table.
Use your table of results to help you answer these questions.
3 a Is basalt more like granite or more like gabbro?
b How do you know?
4 a Is obsidian more like granite or more like gabbro?
Optional extra
Granite
Obsidian
Gabbro
Basalt
Texture of rock
coarse grains
fine grains
Amount of different chemicals found in each type of rock (as a percentage of the total rock)
aluminium oxides
iron oxides
magnesium oxides
silica
other chemicals
14%
3%
1%
72%
10%
16%
11%
7%
50%
Minerals found in rock include:
quartz,
potassium
feldspar,
sodium
feldspar
calcium
pyroxene
Colour of rock
light grey
or brown
dark grey
or black
Data showing chemical and mineral composition of some igneous rocks.
1 Look at your results again. Does the data in this table support your conclusions? Explain your answer.
2 Why do you think granite is described as a silica-rich rock? What evidence is there in the table to support this description?
3 Why do you think gabbro is described as an iron-rich rock? What evidence is there in the table to support this?
4 Fred says 'Iron is more dense than silica. This is why granite is more dense than gabbro'. Is he correct? Why?
8Hd4 The changing Earth
Cut out the labels at the bottom of the sheet, and stick them into the correct places on the diagram.
---------------------------------------------------------------------------------------------------------
mantle
igneous
quickly
magma
slowly
lava
small
large
volcano
8Hd5 Igneous rocks
1 Write the answers to these clues in the grid.
a An igneous rock with large crystals.
b Liquid rock.
c The layer of hot rock under the crust of the Earth.
d If a rock gets hot enough it will _______________ .
e This is where magma escapes through the crust of the Earth.
f The solid part of the Earth, on which we live.
g An igneous rock with small crystals.
h Size of crystals made by slow cooling.
i Lava on the surface of the Earth _______________ down quickly.
j These are different sizes of these in different igneous rocks.
a
b
c
d
e
f
g
h
i
j
2 Write out the letters in the shaded boxes, and add the last missing letter.
3 Now write a clue for these words. ______________________________________________
8Hd6 Mount St Helens
Some volcanoes do not erupt for hundreds of years, and then suddenly erupt without much warning. Mount St Helens in the USA erupted on 18 May 1980. There was some warning, but no-one
knew exactly when the eruption would happen.
The eruption began with a small earthquake, which caused a landslide on the mountain. Experts think that this released the pressure that was holding the molten rock inside the volcano. According to an eyewitness, 'There was a landslide, then the first ash cloud came out and then the explosions really began. It looked just like a forest fire, you could see it burning and churning, kind of rumbling - we were right under it!'
A horizontal explosion blew the side out of the mountain and then a vertical one sent tonnes of ash into the air. The sideways blast vapourised trees and anything else in its path with heat that reached a temperature of 5000 °C. Hundreds of square miles of forest were flattened within 10 minutes of the landslide starting.
About 60 people died in the blast, most buried under tonnes of ash. The north side of the mountain was covered by a 1100 °C flow of pumice (a kind of rock) which burnt up everything in its path. Other areas were buried under an avalanche of melted snow, boulders and soil an average of 45m deep. Near to the blast, trees were uprooted and burnt. The trees which missed the direct blast were coated in a layer of ash up to a metre deep.
Today, the environment is recovering. Plants and trees are growing on most areas. Insects and mammals are thriving - there are even more deer and elk now than there were before the eruption. But the power of this eruption means that this volcano is now studied very closely indeed. There are two neighbouring volcanoes, also inactive for many years, just like Mount St Helens. Both are now studied carefully but nobody knows when the next one might erupt.
1 How could people first see that the volcano was erupting?
2 Why was the earthquake thought to be important in this volcanic eruption?
3 What were the stages in the eruption of the volcano?
4 What damage did the volcano cause?
5 If you lived near to the neighbouring volcanoes how would you feel? What could you do to make sure that you didn't get caught in an eruption like the one described here?
6 The environment is recovering. Think about where the new plants and animals might have come from. Do you think any of them managed to survive the volcanic eruption? If so, how?
7 Scientists can study volcanoes, but they cannot stop them erupting. If this is the case, why do scientists monitor volcanoes? What benefit could there be for the people who live near this volcano? What benefit could there be for people who live near other volcanoes?
8Hd7 A new island!
The dormant Kavachi volcano, in the middle of the Pacific Ocean, has erupted and formed a new speck of land. The Kavachi volcano is at the top of an 800 m underwater mountain located in water 1.1 km deep. Scientists, who happened to be on a ship in the area at the time, first spotted a steaming volcanic beach. Then suddenly, the water boiled up and there was a huge fountain of steam and volcanic ash. Refrigerator-sized chunks of molten lava were thrown 70 m into the air and a 500 m high mushroom cloud formed every 5 minutes - each time the volcano erupted. The eruption was later described as 'a classic clash between a volcano and the ocean'. Shock waves from the volcanic eruptions stunned schools of fish which floated to the surface and were eaten by seabirds. The chemicals from the eruption were detected up to 5 km away from the volcano.
The first recorded eruption of Kavachi was in 1939, and it has erupted at least eight times since then. Each time, the island it created became unstable and collapsed back into the water. Its last recorded eruption was in 1991. One of the scientists in the area explained that the effect was caused by the release of magma from the top of a magma chamber, which is below sea level: 'The magma has a lot of gas in it, so it's a very explosive mixture when it comes close to the surface.'
1 Where is Kavachi?
2 Using the information in the text to help you, draw a scale diagram to show the shape of the sea bed in this region. Make sure you mark the level of the surface of the sea on your diagram.
3 Mark the magma chamber on your diagram.
4 The scientists stayed well away from the erupting volcano. They were afraid that their boat would sink because of the amount of gas in the water. Where would this gas have come from?
5 Imagine that you were one of the scientists who spotted this volcano starting to erupt. A newspaper has asked you to write a report describing what it looked like and how you felt at the time.
6 If this volcano continues to erupt, it might eventually collapse back into the sea again. Draw a series of diagrams to try to explain why. (Hint: Think about where the molten magma came from.)
8He1 Rock bingo
1
sedimentary
slate
2
pressure
granite
transportation
melting
sandstone
weathering
mudstone
particle theory
crystal size
cementation
metamorphic
sediment
acids
3
limestone
4
deposition
minerals
compaction
fossils
porous
basalt
harder
5
6
grains
bigger crystals
7
8
9
10
appearance
DO not make a double sided photocopy of this worksheet
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8He2 Rock 'I've got, whose got…'
transport
sediments
THIS SHOULD BE A DOUBLE-SIDED PHOTOCOPY
The place where magma flows out of the Earth as lava.
Hot, molten rocks within the Earth.
Type of rock formed from other rocks due to high temperature and pressure.
This will be greatest on the rocks at the bottom of a cliff.
The process which drops sediments.
An igneous rock with large crystals.
A metamorphic rock which contains layers of crystals which can be easily split to make roof tiles.
A sedimentary rock containing calcium carbonate.
The process which forms magma from solid rock.
The chemicals which make up rocks.
The process which carries rock particles from one place to another.
Rocks formed when magma turns to a solid.
A sedimentary rock formed from very tiny particles of mud.
An example of a sedimentary rock which is formed from grains of sand.
A metamorphic rock formed from limestone or chalk.
This process breaks down rocks into smaller particles.
These remains are often found in sedimentary rocks.
The theory that everything is made of particles which are constantly moving.
This is decided by how quickly the magma cools when forming igneous rocks.
When sedimentary rocks are formed, the rock grains are squashed together during this process.
Carbonates react with these chemicals.
Sedimentary rocks which soak up water are said to be this word.
Layers of rock grains which build up as more grains are deposited.
When sedimentary rocks are formed, the rock grains are glued together by salts during this process.
Rocks formed from layers of sediment.
These will be formed in igneous rocks when magma cools slowly because particles have more time to group together.
These can be seen in sedimentary rocks but may not be seen in metamorphic rocks.
An igneous rock with very small crystals.
8He3 The rock cycle 1
Cut out these sentences. Match the pairs, and put them in the correct order to describe the rock cycle. Stick them into your book.
Small fragments of rock get transported away …
If the rock is heated enough, it melts …
… are deposited at the bottom of the river.
The layers of sediment gradually get squashed …
… through cracks and volcanoes.
… igneous rocks.
… metamorphic rock.
… squashed under the surface of the Earth.
… and are changed into metamorphic rock.
Some magma rises to the surface of the Earth …
When the river slows down, the bits of rock …
Over many years, these bits of rock …
Some igneous rocks get buried and squashed …
Rocks get weathered by chemical …
… and eventually form sedimentary rock.
Some sedimentary rocks get heated and …
When the magma cools, it forms …
… and forms magma.
… build up to form layers.
… and physical weathering.
This changes the rock into …
… from rock faces by rain, streams and rivers.
8He4 The rock cycle 2
Cut out the labels below and stick them on this diagram to show the rock cycle.
Lava cools quickly on the surface to form igneous rocks with small crystals.
Magma rises to the surface of the earth.
Rocks get weathered by chemical and physical weathering.
Some igneous rocks are changed into metamorphic rock.
If the rock is heated enough, it melts and forms magma.
Some magma gets trapped, and cools underground to form igneous rocks with large crystals.
The layers of sediment gradually get squashed and eventually form sedimentary rock.
Small fragments of rock get transported away from rock faces by rain, streams and rivers.
Some sedimentary rocks get heated and squashed under the surface of the Earth. This changes the rock into metamorphic rock..
When the river slows down, the bits of rock are deposited at the bottom of the river, or sea. Over many years, these bits of rock build up to form layers.
8He5 Uniformitarianism
In 1785, the Scottish geologist James Hutton outlined his ideas about Uniformitarianism. He proposed that the Earth was too old for us to be able to tell its exact age, but that the geological processes which shape the Earth's surface today are the same processes that have shaped the Earth's surface throughout time. For example, if the patterns found in layers of sand at the bottom of rivers today are the same as the patterns found in ancient sandstones, it would suggest that the same kind of river current was flowing then. If this theory is true, the Theory of Uniformitarianism could help us to explain the events that shaped the Earth many millions of years ago.
James Hutton (1726-1797).
Carry out research to find the answers to one of the following questions. Write a report of your findings. You may be able to present your information to the rest of your group.
1 James Ussher worked out that the Earth was about 6000 years old. How did he work this out?
2 In 1779, the French naturalist Comte George de Buffon had proposed that the Earth was much older than the 6000 years suggested in the Bible. What was his evidence that the Earth was much older than was suggested in the Bible?
3 Hutton's work was strongly attacked, especially by some Christian fundamentalists, when it was published. Why do you think this was?
4 In 1830, the first volume of 'The Principles of Geology' was published by another Scottish geologist, Charles Lyell (1797-1875). This work developed Hutton's ideas on Uniformitarianism and dated the Earth at several hundred million years old. What evidence did Lyell use to date the Earth?
5 Lyell's method of explaining past events by looking at what is happening in the present, was applied to biology by Charles Darwin during his writing of the 'Theory of Evolution'. What evidence did Darwin use to support his ideas about evolution?
8H Summary Sheets
The rock cycle
Rocks are made from a mixture of minerals. The shape of rocks can be changed by weathering and erosion. Weathering can occur because of chemical, physical or biological processes.
Sedimentary rocks
Rock fragments, formed as a result of weathering and erosion, are transported by rivers, and the fragments get worn down. Small rock fragments are called grains. When the water slows down, some of the grains are deposited at the bottom of rivers, lakes or seas, and form sediment.
Layers of sediment collect on the sea bed, and the bottom layers get squashed. The grains of sediment are forced closer together (compacted) and the water is squeezed out from between the grains. Minerals in the sediment 'glue' the grains of rock together (cementation). Eventually, sedimentary rock is formed. The composition of sedimentary rocks varies and depends on the way they were formed. For example, there are different types of limestone - chalk is formed from the shells of microscopic animals, coquina is formed from larger shell fragments and oolite is formed from sediments deposited when sea water evaporated.
If any animals or plants get trapped in the sediment, they may form fossils.
Igneous rocks
Molten rock is called magma. If the molten rock flows out of volcanoes it is called lava. Igneous rocks are formed when magma cools down.
Lava cools down quite quickly, and forms igneous rocks with small crystals (like basalt). Magma underground cools down much more slowly and forms rocks, like granite, with bigger crystals.
Metamorphic rocks
Sedimentary or igneous rocks can be changed by heat or pressure into new kinds of rock, called metamorphic rocks. Metamorphic rocks have different properties from the sedimentary or igneous rocks they were made from.
Examples
limestone, sandstone, mudstone, chalk
basalt, granite
marble, quartzite, slate, gneiss
Grains or crystals?
separate grains
crystals
crystals - often in bands of different colour
Hard or soft?
often soft or crumbly
hard
Porous?
often
not usually
The Earth is continually changing. Rocks are weathered and eroded and new rocks are being formed. The processes which make rocks, weather them and change them are linked together in the rock cycle.
8H Target Sheet
Topic
Targets
Before the unit
I have learned this
I have revised this
8Ha
Know the names of some sedimentary rocks.
Know the characteristics of sedimentary rocks.
Know how the pressure on rocks varies.
Know how sedimentary rocks are formed.
8Hb
Know what all rocks are made out of.
Know what limestone is.
Know some of the differences between different limestones.
Know that limestone is a carbonate-rich rock.
8Hc
Know what the word metamorphic means.
Know some examples of metamorphic rocks and the rocks from which they were made.
Know how metamorphic rocks are different from sedimentary rocks.
Know how metamorphic rocks are formed.
8Hd
Know the names of some igneous rocks.
Know how igneous rocks are formed.
Know why igneous rocks can have different sized crystals.
Know how the particle theory can be used to explain the different sizes of crystals in igneous rocks.
8He
Know how the rocks of the Earth change.
Know what the rock cycle is and about the different processes by which rocks are formed.
Know that rocks melt as part of the rock cycle.
Know how rocks are weathered.
8H Word Sheets
Word sheets that include new words from the 'Focus on:' pages are available on the Exploring Science website.
8Ha - Settling Down
Word
Pronunciation
Meaning
sem-men-tay-shun
A process in which water is squeezed out of the spaces between pieces of rock leaving mineral salts behind which stick (cement) the rock pieces together.
cemented
sem-men-ted
Something that has been stuck together.
chalk
Soft white or grey rock formed from the shells of small sea animals.
com-pack-shun
When layers of sediment or rock are squashed by the weight of sediment above them.
deposits
When moving water drops rock fragments or grains.
fossil
The remains of a dead animal or plant that became trapped in layers of sediment and turned into rock.
grain
Tiny, rounded piece of rock.
A sedimentary rock made from the shells of dead sea creatures consisting mainly of calcium carbonate.
The chemicals that rocks are made from.
poor-us
Porous rocks can soak up water.
A sedimentary rock made from rounded grains of sand.
Rock grains and fragments dropped on the bottom of a river, lake or sea.
sedimentary rock
Rock formed from layers of sediment.
shale
A sedimentary rock.
The movement of rock grains and fragments by wind or water.
weathered
Rocks that have been worn away or broken up by chemical, biological or physical processes.
8Hb - Fossils and limestone
carbonate-rich
Something which contains a lot of compounds called carbonates.
Any sign of past life that has been preserved in a rock.
A sedimentary rock made from the shells of dead sea creatures.
oolite
oo-lite
A type of limestone formed when water evaporates and leaves calcium carbonate behind.
8Hc - All change!
Molten rock beneath the surface of the Earth.
A metamorphic rock formed from limestone.
met-a-mor-fik
A word meaning 'changed'.
metamorphic rocks
Rocks that have been formed by changing igneous or sedimentary rocks.
A sedimentary rock made from mud.
quartzite
kwartz-ite
A metamorphic rock formed from sandstone.
A metamorphic rock with tiny crystals, formed from mudstone.
8Hd - A river of rock
ba-salt
An igneous rock with very tiny crystals.
bonds
Forces holding particles together.
crust
The solid rocks at the surface of the Earth.
crystal
kris-tal
Piece of mineral with sharp edges.
gran-it
igneous rock
igg-nee-us
A rock formed when magma or lava cooled down and solidified.
lar-va
Molten rock that runs out of volcanoes.
man-tel
The part of the Earth below the crust.
particles
The tiny pieces that everything is made out of.
A place where lava flows out of the Earth.
8He - Rolling on
rock cycle
All the processes which form sedimentary, igneous and metamorphic rocks, linked together.