3 geology · rocks 13 copy and complete: _____ are the building blocks of rocks. 14 clay and sand...

3Students:

expand their knowledge of science to include abstract concepts, theories, principles and models

explore how scientific work has led to an understanding about the natural world and changed our understanding of ourselves and our possible destiny

use fossils and other information to construct a time scale for the history of Earth

use a classification system for living things, past and present.

Students:

explain the relationships, past and present, in living and non-living systems

use time scales to explain the changing Earth and its place in space

use physical and theoretical models to investigate geological processes.

1 What is a rock?

2 A dentist’s drill usually contains diamond pieces. Why?

3 True or false? Rocks can be made out of dead animals.

4 How can scientists tell the age of an Aboriginal painting?

5 Is petrified wood a fossil or a piece of wood that is really frightened?

6 How do scientists know about animals like the dinosaurs that have been extinct for millions of years?

7 Why did dinosaurs often have rocks in their stomachs?

8 What killed off the dinosaurs?

Getting started

Learning focus

Standards: Science knowledge and understanding

LEVEL 5

Geology

SciDim2CB_Ch03.indd 53SciDim2CB_Ch03.indd 53 11/1/06 4:09:04 PM11/1/06 4:09:04 PM

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3.13.1Rocks may not be alive, but they can still tell us quite a lot about the past. Geology is the study of the Earth, its rocks, minerals, volcanoes, earthquakes, fossils and much more. Mineralogy is a branch of geology that studies minerals. Petrology is the study of rocks themselves and how they are formed.

MineralsA mineral is a naturally occurring substance with its own particular chemical composition and structure. Minerals are found in the Earth’s crust (lithosphere) in beautiful shapes called crystals. Quartz, mica and feldspar are examples of minerals. Minerals are the building blocks that make up rock.

Almost all minerals (99 per cent of them) are made up from only eight elements—oxygen (O), silicon (Si), aluminium (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K) and magnesium (Mg). The two most common elements that make up the Earth are oxygen (O) and silicon (Si), so it is not surprising that

PiezoelectricityWhen two brothers,

Pierre and Jacques Curie, sandwiched a thin slice of quartz between two layers

of tin and applied pressure to it in 1880, they detected a short pulse of electricity. Many years later, scientists

realised this so-called ‘piezoelectricity’ could be

generated using tiny quartz crystals, and could be used

to keep time in watches and clocks.

these elements are also common in minerals. Quartz is made up of silicon and oxygen.

Some minerals are made up of only one metal element and are known as native metals. Gold, silver and platinum are native metals.

Characteristics of mineralsMinerals have several characteristics or properties that help geologists differentiate between them.

What’s in a name?Parasite is a mineral found

in the central American country of Columbia, apatite is a mineral

containing phosphates that can be used as a fertiliser

and crocidolite is an asbestos mineral!

Fig 3.1.2 Native silver

Fig 3.1.1 Quartz (left), mica (middle) and feldspar (right) are all minerals.


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Crystal structureMany minerals have a distinctive crystal structure. In ancient times it was believed that quartz crystals were composed of water that had frozen so solid it could never melt. Logically, the word ‘crystal’ comes from the Greek word kyros, meaning ‘icy cold’. The overall shape formed by a mineral’s crystals is called a habit.

monoclinic(augite)

hexagonal(emerald)

cubic(diamond)

orthorhombic(olivine)

triclinic(plagioclase)

tetragonal(zircon)

Fig 3.1.3 Most crystals have one of the structures shown here.

Some crystals have an internal structure that causes them to break apart more easily in some directions, along cleavage planes.

Fig 3.1.4Several cleavage planes may be seen in these crystals.

Homework book 3.1 Crystals

Wulfenite has distinctive flat crystals. Fig 3.1.5

LustreEach different crystal structure reflects light differently. Lustre refers to the way a mineral reflects light.

This azurite (a copper compound) sample contains high-quality blue pigment. Fig 3.1.6

HardnessMinerals have a characteristic hardness. A mineral is harder than another if it is able to scratch it, without getting scratched itself. In 1812, an Austrian mineralogist, Frederic Mohs, invented a scale of hardness from 1 to 10, with 10 being the hardest and 1 being the softest. A mineral is able to scratch any mineral lower than it on Mohs’ scale.

Pigment and streakMinerals often have a distinctive colour called pigment. They can be crushed into powders to colour paints. Some of these minerals are toxic and most have now been replaced by safer synthetic dyes.

The term streak is also used to describe the colour of a powder made from a mineral. Streak can be seen when a mineral is rubbed on an unglazed white tile. Some minerals do not produce a streak, and others have a streak that is a different colour from the mineral itself. Prac 1

p. 59

3.13.1


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>>>Mohs’ scale of hardness

1 talc

2 gypsum

3 calcite

4 fluorite

5 apatite

6 orthoclase

7 quartz

8 topaz

9 corundum

10 diamond

Hardness of some common objects

fingernail 2.5

copper 3.5

iron nail 5.5

glass 5.5

steel knife 6.5

emery board 8.5

A dentist’s drill needs to be harder than a tooth and so has diamond pieces on its surface. Fig 3.1.7

Prac 2 p. 59

The white body paint used in Aboriginal ceremonies is made from pipe clay and gypsum. Fig 3.1.8

Fig 3.1.9 Powdered ochre was used to make these Aboriginal rock paintings on the Chamberlain River in northern Western Australia.

Aboriginal painting

Aboriginal people traditionally use pigments (or ochres) from nature for the colours of their paintings. They grind up minerals from the local rocks and blend them to get the right colours. Often each colour has a special meaning. Blood is red, the pigment coming from rusty-coloured pebbles of haematite, containing iron oxide (Fe2O3) (rust). Bones are white, its ochre coming from a clay called kaolin found in creek beds. Fat is yellow and skin is brown, both pigments (called limonite) coming from well-worn pebbles in creek beds. Black comes from the charcoal of fires. To make paint, pigments are mixed with juices, egg or blood.

Uses of mineralsMinerals have many uses. Some of them are listed in the table below.

Mineral Uses

salt food preservative, source of sodium and chlorine

graphite ‘lead’ in pencils, electric motors

phosphate matches, fertilisers

tungsten light-bulb filaments, saw blades and drill bits

sulfur used to make sulfuric acid, fertiliser

Rocks and mineralsRocks and minerals


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3.13.1RocksThe study of rocks is a branch of geology known as petrology. A rock is made up of minerals. Granite is a rock made from three minerals—quartz, mica and feldspar. Limestone rock contains only one mineral—calcium carbonate. Rocks usually contain no more than six minerals. Clay and sand are types of rock, although crushed into very small pieces.

Fig 3.1.10 The rock granite is made from the minerals quartz, mica and feldspar.

Haematite (iron ore) occurs in several forms, including so-called kidney ore. Fig 3.1.11

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[ Questions ]Revision questions

Minerals 1 What is the difference between geology and petrology?

2 What is the study of minerals called?

3 What is a native metal?

4 Give three examples of native metals.

Characteristics of minerals 5 List four characteristics of a mineral.

6 Sketch two types of crystal structure.

7 What structure allows some minerals to be broken more easily in one direction than another?

8 Why have mineral pigments been largely replaced by synthetic dyes in paints?

9 Who invented the scale of hardness?

10 What is the hardest mineral on this scale?

Uses of minerals 11 List five minerals and what they are commonly used

for.

12 How do Aboriginal artists use pigments from minerals?

Rocks 13 Copy and complete: _______ are the building blocks

of rocks.

14 Clay and sand don’t look like rock; why are they classified as rock?

>>

OresOres are rocks or minerals that contain elements that may be extracted for profit. Iron, for example, is extracted from an ore called haematite. Aluminium is extracted from the ore bauxite.

Ore Element that may be extracted

azurite copper

bauxite aluminium

carnotite uranium

cassiterite tin

chalcopyrite copper

galena lead

haematite iron


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Ores 15 Define the word ‘ore’.

16 Which ore contains:a ironb aluminium?

Thinking questions

17 Each of the following statements is incorrect. Rewrite each to make it true:a A mineral is any substance found in the ground.b All minerals are made up of two elements.c Gold and silver are metals, not minerals.d Mineralogy is the study of rocks.

18 Why wouldn’t iron ever be found as a native metal?

19 Suggest what a traditional Aboriginal artist would mix to make the colour grey.

20 A bird’s nest made of clay was found stuck on one of the paintings in the rock shelter shown in Figure 3.1.9. Parts of the bird’s nest was dated as being 15 000 years old.a Suggest what the age is of the paintings underneath

the nest.b Suggest why this was a better method of dating than

taking a sample of the painting itself.

21 Gneiss contains feldspar, quartz, mica and hornblende. Which of these:a are mineralsb is a rock?

22 Name two ore types that contain an element in common and name the element.

23 True or false?a Clay is a type of rock.b All rocks contain only one type of mineral.c Ore is a type of mineral.

Analysis questions

24 If you were a traditional Aboriginal artist, what pigments would you use to paint the Aboriginal flag?

25 Draw a line representing Mohs’ scale of hardness. Mark on it where each of the following would go.a fingernailb copperc iron nail

26 Rank the following minerals from softest to hardest

apatite calcite talc quartz diamond

27 Would:a orthoclase scratch gypsumb quartz scratch topazc calcite scratch your fingernail?

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at workSurfing

Companion WebsiteFind out more about minerals and their uses by connecting to the Science Dimensions 2 Companion Website at www.pearsoned.com.au/schools, selecting Chapter 3 and clicking on the Web Destinations button.

Researching mineralsSurf your available resources (textbooks, encyclopaedias, Internet, etc.) to:

• investigate types of gemstones, their characteristics and where they are found

• find out what lapidary is• find out what a carat is• find the location of Australia’s major known mineral

deposits.

Present your work in one of the following ways:

• a labelled map• a flow chart showing the mining of gems or the

process of lapidary• an information card to educate people who are about

to choose gems.

3.1 SCIENCE

Rocks and mineralsRocks and minerals


http://wps.pearsoned.com.au/sd2

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3.13.1

[ Practical activities ]3.1U

NIT Making a crystal

You will needCopper sulfate, 250 mL beaker, craft stick, Petri dish, Bunsen burner, tripod, gauze mat, heat-proof mat

What to doPart A Obtaining a seed crystal 1 One-third fill a 250 mL beaker with water and dissolve

as much copper sulfate in it as possible.

2 Heat the solution and add more copper sulfate in small amounts until no more will dissolve.

3 Remove the solution from the heat and allow it to settle and cool for about 5 to 10 minutes.

4 Carefully decant enough of the solution to make a shallow layer in a Petri dish and allow this to cool overnight. Keep the rest of the solution in the beaker.

Part B Growing a large crystal 1 Obtain a small seed crystal from the Petri dish (or ask

another group for one if yours did not produce any).

2 Tie it to a piece of cotton thread and suspend it in your cooled copper sulfate solution.

Prac 1 Unit 3.1

3 Observe the crystal every few days for a week or so.

Questions

1 Your initial solution was saturated. What does this mean?

2 Sketch the crystal (after it has grown).

3 Do copper sulfate crystals have obvious cleavage planes?

Observing rocksYou will needSelection of rocks and minerals, spatula or iron nail, unglazed white tile, glass stirring rod, piece of copper, emery board, access to stereo microscope or magnifying glass

What to do 1 Construct a table like that shown below.For each rock or mineral, complete the following tasks.

2 Record its colour or pigment.

3 Rub the rock or mineral against the white tile. Record the colour of any streak left on the tile.

4 Record how lustrous the rock or mineral appears to be; that is, does it sparkle, does it reflect light or is it dull?

5 Use a magnifying glass or stereo microscope to observe any crystals. Identify their shape or draw what they look like.

6 Try to scratch the rock or mineral with your fingernail, spatula or iron nail, glass stirring rod, piece of copper and emery board. Estimate what number on Mohs’ scale your specimen would be.

Questions

1 List the rocks and minerals you tested in order from softest to hardest.

2 On what does lustre depend?

3 What is the difference between a rock and a mineral?

Prac 2 Unit 3.1

Rock Colour/pigment Streak Lustre Crystal shape Hardness

Making a crystal

icy pole stick

seed crystal

copper sulfate solution

Fig 3.1.12


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3.23.2Classifying rocks according to the minerals they contain would be too difficult and result in too many categories. Instead they are classified according to how they were formed. This results in three main types of rocks: igneous, sedimentary and metamorphic.

Igneous rocksIgneous comes from the Latin word ignis, meaning ‘fire’. It is not surprising then that igneous rocks are formed when molten material from within the Earth cools and becomes solid. Molten material is called magma when it is below the Earth’s surface, and lava when it is above the Earth’s surface. Magma reaches the Earth’s surface when volcanoes erupt.

Intrusive igneous rocksWhen magma cools slowly below the Earth’s surface it forms intrusive rocks. The word ‘intrusive’ means ‘forced in’, which is exactly what happens when magma is squeezed between other rock layers under the ground. Intrusive rocks contain large interlocking crystals. Granite is an example of a slow-cooling igneous rock in which crystals can be seen with the

naked eye. Although formed underground, granite often becomes visible above ground when erosion or movement of the tectonic plates uncover it.

Extrusive igneous rocksLava cools more quickly than underground magma because it is above the Earth’s surface. Cooling lava forms extrusive rock. The word ‘extrusive’ means ‘pushed out’. Crystals formed are small or non-existent. Basalt is an example of an extrusive igneous rock containing tiny crystals. The ocean crust is made of basalt.

Lava forms extrusive igneous rock when it cools and solidifies. Fig 3.2.2

Uses of igneous rocksIgneous rocks like granite and basalt are extremely hard and are useful building materials. Scattered across much of western Victoria are long-dead volcanos. The lava they spewed out thousands of years ago levelled large areas of the landscape and laid a foundation of basalt (or bluestone) under most of western Victoria and much of Melbourne. Bluestone is a common sight around inner Melbourne, having been used in buildings, gutters and lanes.

How extrusive and intrusive igneous rocks are formed

volcano

extrusiveigneousrock

intrusiveigneous rock

lava

sill

dyke

magma

Fig 3.2.1

Prac 1 p. 66


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Uses of granite Uses of basalt

bridges bridges

buildings buildings

kitchen benchtops crushed and placed under railway sleepers

gravestones crushed and covered with tar to make bitumen roads

• Sediment first builds up to form a layer. This could be at the bottom of a river bed or the sea. Pressure from the material above squeezes out any air or gaps that might exist in the sediment at the bottom of the layer. The particles then interlock.

• Water seeps through the sediment carrying with it minerals that cement the particles together even more strongly.

Sedimentary rock Made from

sandstone sand

mudstone mud

conglomerate particles of different sizes

limestone remains of sea organisms (e.g. fish, corals)

chalk skeletons of tiny sea animals

coal compressed plant material.

Ancient toolsAxes made from igneous rocks have been found in ancient Aboriginal quarries near volcanic outcrops in Kakadu National Park, Northern Territory. These axes have been dated using scientific methods and found to be over 20 000 years old. Another igneous rock called greenstone was by mined by Aboriginal people at Mt William near Lancefield in central Victoria. Greenstone is hard, fine grained and perfect for axes and was traded with other tribes.

Fig 3.2.3The hardness of igneous rocks made them perfect for tools such as this

Aboriginal axe-head.

The sedimentary rock layers are obvious in the ‘beehives’ section of the Bungle

Bungle Ranges, Purnululu National Park, northern Western Australia. Fig 3.2.4

Conglomerate rock, also in the Bungle Bungle RangesFig 3.2.5

Sedimentary rocksSedimentary rocks derive their name from the Latin words sedimentum, meaning ‘settling’, and sedere, meaning ‘to sit down’. They are made from sediment which is itself made from small, broken-down bits of other rocks and the remains of animals and plants. This material has been compressed and stuck together in a process known as lithification.

There are two main stages in lithification:

Tourist-attracting rocks

Kata Juta (the Olgas) are a group of thirty or so huge rocks in central Australia

that are the weathered remains of conglomerate

rock, a type of sedimentary rock. The largest of these rocks reaches 546 metres

above the surrounding ground level.

3.23.2


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>>>constructed from it. This also means that inner Sydney looks very different and brighter in colour to inner Melbourne, much of which has the colour of the dark bluestone.

Metamorphic rocksPressure-cooker conditions deep in the Earth’s crust can change rocks into new types of rocks. The word ‘metamorphic’ comes from the Greek words meta meaning ‘change’ and morphe meaning ‘form’. A metamorphic rock is one that has changed form.

Sedimentary, igneous or even metamorphic rocks may be changed by heat and pressure within the Earth. A rock made this way is stronger than the original material because its particles are fused together. This is similar to squeezing a snowball to make it stronger.

Original rock

Original rock type

Changed by Metamorphic rock

limestone sedimentary heat marble

granite igneous heat, pressure gneiss (pronounced nice)

shale sedimentary pressure slate

slate metamorphic heat, pressure schist

schist metamorphic heat, pressure gneiss

Fig 3.2.6 The white cliffs of Dover in England are made of powdery chalk composed of the tiny skeletons of sea creatures over 70 million years old.

Types of rocksTypes of rocks

Oyster mortarThe first white settlers of Sydney had no limestone

from which to grind lime for mortar used in

bricklaying. Instead they collected the oysters that

were in abundance around Sydney harbour, and

burnt and crushed them to produce the lime needed.

Prac 2 p. 66

Uses of sedimentary rocksSedimentary rocks are easy to split and are often used as building or paving materials. Limestone can

be used as a building block or be ground up to make cement, a key ingredient in concrete and mortar, two of the most important building materials of all. Coal is burnt to provide power for electricity generation and heating.

Sandstone comes in a variety of colours, and blocks of it are used to make bridges and buildings. Sydney is built on sandstone and it is not surprising that its early buildings, bridges and gutters were

Fig 3.2.8 Gneiss (pronounced nice) is a metamorphic rock that frequently contains bands of different minerals. Bends in the bands indicate where enormous pressure has folded the rock.

Fig 3.2.7These limestone stalactites are sedimentary rocks

caused by dripping water carrying dissolved

chemicals.

Stalactites and stalagmites

Stalactites and stalagmites are fascinating natural structures formed when slightly acidic rainwater

dissolves calcium carbonate (lime) out of sedimentary rock. This lime solution may then drip from the roof of a limestone cave, leaving deposits on the ceiling (stalactites) and floor (stalagmites) when the

water evaporates.


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3.23.2Marble is a popular material

for kitchen benchtops, buildings and sculpture because of its beautiful patterns and dense composition. The Taj Mahal in India is made of marble, studded with semi-precious gems. Slate is a metamorphic rock that splits easily because of its flat, parallel crystals. This makes it useful as roofing tiles, floor tiles and for billiard table tops.

The rock cycleRocks get made, but they are also weathered and eroded. Weathering is when a rock is broken down into smaller particles such as pebbles, soil or sand. This can happen in three different ways.• Physical weathering: Wind, the water from waves

and rivers, ice from glaciers and dramatic changes in temperature can all wear down and crack rock, breaking it down.

• Chemical weathering: Water and chemicals in the air (particularly pollutants) can react with rock and dissolve it.

• Biological weathering: Animals scratch at rocks to find food and to build burrows. Plant roots get into cracks forcing them apart.

Homework book 3.2 Rock types

The rock cycle

weathering breaks down rocks, erosion occurs

igneous rocks formed from molten rock

heat and/or pressure form new, metamorphic rocks

continental crust

sediments pulled deeper by movement of tectonic plates

mantle

ocean crust

sediments build up and compact to form layers of sedimentary rock

sediments fall to the bottom of rivers and oceans

Fig 3.2.10

More about weathering can be found in Science Dimensions 1.

Once broken down, the small particles of rock can be moved to another spot by animals, water and wind. This is called erosion. Eroded soil settles when it stops moving and might form new sedimentary or metamorphic rock if the conditions are right.

The Taj Mahal in India is made of white marble. It was built by the emperor Shah

Jahan as a tomb for his wife Mumtaz. Fig 3.2.9In the barrel

of a gunIn the late 1700s,

geologists Sir James Hall and James Hutton

successfully proved that heat and pressure could change limestone into

marble by sealing some limestone in a gun barrel and roasting it over a fire.


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>>>

heat

Igneous rocks

Sedimentary rocks

weatheringerosion

weatheringerosion

weatheringerosion

compaction and cementing

sediments

pressure

Metamorphicrocks

heat pressure

cooling

melting

magma

Meltingmelting

Fig 3.2.11 A simplified rock cycle

Types of rocksTypes of rocks

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Igneous rocks 1 Copy and complete: Rocks are classified according

to _______ .

2 What does the Latin word ignis mean?

3 What’s the difference between:a magma and lavab intrusive and extrusive rocksc a dyke and a sill?

4 How does the rate of cooling of molten rock affect crystal formation?

5 Name two igneous rocks.

6 Describe a use for a particular igneous rock.

7 How old are some ancient Aboriginal axes found in Kakadu National Park?

8 What rock is much of inner Melbourne built from?

Sedimentary rocks 9 What is:

a sediment b lithification?

10 Name two sedimentary rocks and describe what they are made from.

11 Give two reasons the particles in a sedimentary rock stick together.

12 Inner Sydney is built predominantly from what rock?

Metamorphic rocks13 Name two things that may affect rocks in the

Earth’s crust.

14 Name two metamorphic rocks, and name their ‘parent’ rocks.

The rock cycle 15 List three types of weathering.

16 What is the difference between erosion and weathering?

Thinking questions

17 If granite is formed underground, how is it that granite boulders can be seen above ground in Euroa and Seymour in Victoria?

18 Draw a sketch explaining the difference between a stalactite and a stalagmite.

19 Give a brief description of the main rock types.

20 Suggest why marble is sometimes used to make cutting boards for food.

21 What type of rock is:a chalk d marble g coal?b limestone e greenstone c basalt f sandstone

Analysis questions

22 Copy and complete the schematic diagram of the rock cycle in Figure 3.2.12.

erosion

igneous rocks

m

elting

c

oolin

g

melting

heat

/pressu

re

erosio

n

melting

heat

/pre

ssur

e

Fig 3.2.12 >>

Homework book 3.3 The soil texture triangle


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3.23.2

23 Label each rock in Figure 3.2.13 as either igneous (intrusive), igneous (extrusive), sedimentary or metamorphic.

Fig 3.2.13

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at workSurfing

Companion WebsiteFind animations that show how rocks are created by connecting to the Science Dimensions 2 Companion Website at www.pearsoned.com.au/schools, selecting Chapter 3 and clicking on the Web Destinations button.

Researching UluruSurf your available resources (textbooks, encyclopaedias, Internet, etc.) to find details on one of the following.

1 What rock is Uluru (formerly known as Ayers Rock) made from and how was it formed? What is its importance to the local Aboriginal people? Who runs the Uluru National Park?

2 How is coal formed? What are the differences between brown and black coal, where are they both found and what are they used for?

Present your work as a combination of the following ways:

• a poster• a Word document• a flow chart showing how Uluru or coal is formed• a pamphlet for tourists visiting Uluru or a coal mine.

3.2 SCIENCEImagining

Volcanic eruptionYou are Ignis, a tiny piece of rock way under the Earth’s surface. You are about to be spewed out in a volcanic eruption. Describe your journey, your fate and the fate of your fellow rocks. Describe the temperatures, pressure and how you and your rock-mates feel at each stage.

Present your work in one of the following forms:

• an oral children’s story• a role play• a written short story• a dance (with music).

Investigating

Sedimentary rocksInvestigate the properties of artificial sedimentary rocks made from various combinations of sand, dry clay, small stones, plaster mix and water.

Present your work as an experimental report. Include all the normal features, such as aim, materials, method, results and conclusion.



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>>>Types of rocksTypes of rocks

[ Practical activities ]3.2U

NIT Growing crystals at different temperatures

cold water air onlysaturated coppersulfate solution

Fig 3.2.14Crystals and cooling ratesYou will needCopper sulfate, two 100 mL beakers, two 500 mL beakers, one 250 mL beaker, stirring rod

What to do 1 One quarter fill the 250 mL beaker with water and

use a stirring rod to dissolve as much copper sulfate in it as possible.

2 Heat the solution and add more copper sulfate until no more will dissolve (a saturated solution).

3 Place half of the saturated solution in each of the two 100 mL beakers.

4 Place one 100 mL beaker in a 500 mL beaker with some cold water and the other in a 500 mL beaker containing air only.

5 Observe any crystals formed overnight.

Prac 1 Unit 3.2

RockmakerConcrete is made from a combination of two or more of the following: cement, sand, crushed rock, water. In this experiment, you will make various types of concrete.

You will needCement (dry, powdered), sand, finely crushed rock, plastic teaspoon, paper or plastic cups

What to do 1 In one cup, place three teaspoons of sand and three

teaspoons of cement. Label this cup 3S, 3C.

2 In another cup, place four teaspoons of sand and two teaspoons of cement. Label this cup 4S, 2C.

3 In another cup, place two teaspoons of sand and four teaspoons of cement. Label this cup 2S, 4C.

4 In another cup, place three teaspoons of finely crushed rock, two teaspoons of sand and one teaspoon of cement. Label this cup 3R, 2S, 1C.

5 Now gradually add a small amount of water to the first cup and mix until you get a thick, even paste. Repeat for the other cups.

6 Leave each cup to dry overnight.

7 Test the strength of each concrete sample.

Questions

1 Why was it important to have the same total amount of ingredients in each case?

2 Which sample was strongest?

3 Do you think concrete setting is a physical or chemical change? Why?

Prac 2 Unit 3.2

Questions

1 Describe any crystals formed.

2 List any key differences between the two sets of crystals.

3 What caused larger crystals to form?


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3.3The Earth is constantly changing. Volcanoes explode, coastlines wash away and animals and plants become extinct for all sort of reasons. Although it is hard to imagine brand new animals and plants forming, brand new bacteria and viruses are forming every day.

In the seventeenth century, biblical records were used to calculate the age of the Earth: they suggested that it was created around 4004 BCE. The growth rings in some trees, however, show that they are older than this. More recently, the

radioactivity of rocks has been used to estimate the ages of rocks in the Earth’s crust. Evidence now indicates that Earth is about 4.5 billion years old.

Types of fossilsThe story of life on Earth is told by its fossils. Palaeontology is a branch of geology that studies them. A fossil is evidence of past life found in a rock—usually sedimentary rock. This evidence may be:• bones, teeth, shell or a complete skeleton• part of an animal or a

complete animal preserved by a rare freak of nature. Ancient insects have been found trapped in amber (sap from a plant). Woolly mammoths have been found in frozen soil in Siberia in Russia so perfectly preserved that they still have flesh, hair and stomach contents. Sabre-tooth tigers have been found in tar pits in Los Angeles and even human bodies have been found preserved in ice or the mud of bogs

• a mould in the exact shape of the animal. The mould sometimes fills naturally with quartz, limestone or other natural chemicals that harden to form a cast. Occasionally opal fills the mould. If the mould is empty, then plaster or molten plastic can be added to make an accurate cast or model of the animal

The sabre-tooth elephant

When American scientists assembled the first

skeleton of a mammoth in the late 1700s, they

attached its tusks up-side down to make it look as

ferocious as a sabre-tooth tiger and gave it claws that actually came from a giant

extinct sloth.

• a footprint or footprints. These can also be filled to make a cast

• a mineral petrified replica of the bone, shell or even wood. Minerals sometimes slowly replace the original material as it decays away, leaving a stone replica of it. This is called petrification

• an image of the animal or plant. Heat may burn away everything except black carbon, which is left as an image of the organism. A carbonised fossil has been formed.

Fig 3.3.1 100-million-year-old casts of animals called ammonites

Fig 3.3.2The bones of an Ichthyosaurus have been replaced by minerals to form this fossil.

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3.3


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Fossil formationFossils are created when the remains of an animal or plant are covered by sediments (dust, sand or mud) and become part of the sedimentary rock that is formed. Figure 3.3.4 shows the steps in the formation of a fossil of a now-extinct animal called an ammonite.

Most dead animals and plants never form fossils, however, because:• most decay too quickly for

them to be preserved• their bodies are eaten or

scattered by scavengers like vultures

• most are too fragile and are crushed, leaving nothing to be preserved

• they die in the wrong spot. Eighty-five per cent of all rock is inappropriate for fossil production. Fossils are never found in igneous rocks, for example, since any remains would have been destroyed by the hot lava or magma

• millions of years of the rock being folded and faulted break up any fossil formed into unrecognisable bits.Many of the fossils that are successfully formed

will never be found or studied by scientists because they are buried too deep, are in remote locations or are not recognised as important by the villagers or farmers that find them.

Dating fossilsLayer upon layerYou are taking a trip through time whenever you dig a hole. The oldest soil and rock will usually be at the bottom of the hole and the youngest will usually be on or near the top. Likewise, the oldest fossils are usually

Prac 1 p. 74

Fig 3.3.3A human fossil plaster cast—this unfortunate person died under a layer of volcanic ash after

Mount Vesuvius erupted in 79 CE.

Fossil formation

dWeathering and erosion may eventually wear away some of the rock to expose part of the fossil. Fossils are often found in road cuttings or quarries.

aAn ammonite dies and falls to the bottom of the sea where it is covered by sediments and protected from being eaten by other animals. The soft parts of its body decay, leaving just the shell.

bMore and more sediment covers and squeezes the shell. The shell may remain or be replaced with minerals such as quartz or limestone that seep into it in solution before the original shell dissolves.

cAfter millions of years, movement in the Earth’s crust may thrust the layer of sedimentary rock containing the fossil upwards to form part of a mountain range.

Fig 3.3.4

FossilsFossils

1 in 120 000It has been estimated that fossils have been found for only one out of every

120 000 creatures that have ever lived on Earth. This means that we have no

fossil record for the vast majority of creatures now

extinct, meaning scientists have little idea about them.

Most fossils that we do have are of animals that

once lived in shallow seas.


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found in deeper layers, with the youngest near the surface. Palaeontologists can judge a fossil’s age by the depth at which it was found.

Fossils that lived over a comparatively short period of time and were widespread are called index fossils, and can help determine the age of a layer of rock. For example, the presence of different species of ammonite allows geologists to date some layers of rock around the world to within a million years or so. The presence of more primitive ammonites indicates a region is older than one containing more evolved ammonites.

All plants and animals contain tiny amounts of radioactive carbon. Its decay can be used to date fossils less than 70 000 years old.

She sells sea shells …

In 1812, at age 12 years, Mary Anning helped

her father find fossil sea shells in Dorset, England,

which they sold. While doing this, Mary made a famous discovery—the

first complete fossil of an Ichthyosaurus! Mary went

on to find many other fossils. It is rumoured that Mary was the inspiration

for the famous tongue twister, ‘She sells sea

shells by the sea shore’.

Fig 3.3.5 The walls of Geike Gorge in the Kimberleys in Western Australia are really the remains of a coral reef.

Radioactive datingRocks can contain radioactive substances that gradually change into other substances over a long period of time. This is known as radioactive decay.

Uranium (U) is a radioactive substance found in many rocks. Over time it slowly decays into lead (Pb). The age of a rock can be determined by comparing the amount of uranium with the amount of lead in it. This type of radioactive dating is used to determine the ages of fossils more than 100 million years old. Tiny sand grains found in Western Australia have been estimated to be 4250 million years old using this technique.

Uranium (U) decays to make lead (Pb). The relative proportions of each can tell the age of a rock.

U UUUUUU

U U U

U

U

UUUUU U U

U

U U U U

U

U

UUUU U

U

U

UUU

UU

U U

U UUU

U

U

UUU

U

U U UU

U

UUU

U U

Creation of rockRatio 100% U, 0%Pb Ratio 50% U, 50%Pb Ratio 25% U, 75%Pb

713millionyears

713millionyears

PbPbPb

Pb PbPb Pb

PbPbPb

Pb PbPb Pb

Pb

Pb

PbPb PbPb

U U

UU

UU

UU

U

U

PbPbPb

Pb PbPb Pb

PbPbPb

Pb PbPb Pb

Pb

Pb

Pb

Pb

Pb PbPb

Pb

Pb Pb

Pb

PbPb

Pb PbPb

Fig 3.3.6

Prac 2p. 74

Geological time scaleIf the complete 4.5-billion-year history of Earth was condensed into a single year, then modern humans or Homo sapiens would have appeared only in its last 5 minutes. Since no humans were present for the rest of the time, scientists have had to use rocks, fossils and radioactive dating to construct the history of Earth. This timeline is divided into eras, with each era divided into smaller periods.

Fig 3.3.7 The Grand Canyon, USA

A grand fossil record

The Grand Canyon in the USA is the second deepest open cutting in the Earth’s surface. It was formed by the Colorado River and is 1.5 kilometres deep.

Layers of rock at various depths provide fossil

evidence of life described in the table on page 70. The deepest cutting is an almost inaccessible and lonely gorge in the Himalayan Mountains

in China.

3.33.3


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Most of the animals that have lived on Earth no longer exist, at least not in their original form. Mass extinctions of animals and plants have occurred several times in Earth’s history. These extinctions took

relatively little time, suggesting that some massive calamity hit the planet. The extinction of the dinosaurs is an example of this.

Era Period Millions of years ago (mya)

Life/comments

Cenozoic (recent life)

Quaternary 0–2 Humans (Homo sapiens)

Tertiary 2–65 Mammals and birds become dominant after extinction of the dinosaurs

Mesozoic (middle life)

Cretaceous 65–144 Final period for dinosaurs; small mammals, flowering plants; Tyrannosaurus lived around 65–68 mya

Jurassic 144–208 Plant-eating dinosaurs abundant, flying reptiles, first birds; Apatosaurus (formerly Brontosaurus) lived around 150–156 mya

Triassic 208–248 Dinosaurs, tiny mammals

Palaeozoic (ancient life)

Permian 248–290 Modern insects; new mountains, deserts

Carboniferous 290–362 Reptiles evolve from amphibians

Devonian 362–408 Many types of fish, first land animals, amphibians, tree-sized land plants

Silurian 408–438 Early simple land plants, first insects

Ordovician 438–505 Fish, corals, molluscs

Cambrian 505–570 Worm-like creatures, first vertebrates—eel-like animals, animals with shells (e.g. trilobites)

Proterozoic (earlier life)

Precambrian 570–2700 Single-celled animals, early sea plants, fungi

Archaeozoic (primitive life)

2700–3500 First signs of life—algae and bacteria

Azoic (without life)

3500–4600 No life; Earth still cooling after its creation

FossilsFossils


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Fig 3.3.8 This trilobite fossil is 5 cm long and 400 million years old. There were many types of trilobites, some the size of a beetle, others the size of a large plate.

The horseshoe crab of today is thought to be a distant relative of the trilobite. Fig 3.3.9

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Types of fossils 1 How old do scientists currently believe the Earth to be?

2 What is a fossil?

3 Explain different ways fossil casts can be made.

4 Explain how an image of a fossil is made.

5 What animals have been found intact?

6 What conditions preserve creatures intact?

Fossil formation 7 Construct a flow chart to show how a fossil can form.

8 Why are fossils found in sedimentary not igneous rock?

9 List five reasons why fossils will not form.

10 Many fossils will never be found. Explain why.

Dating fossils 11 List three ways fossils can be dated.

12 Give an example of an index fossil.

13 What does uranium change into over time?>>

Extinction then allows other species to emerge and dominate their environment. Animals called trilobites appeared about 540 million years ago and then vanished 300 million years later, allowing crustaceans to become abundant. Today there are over 30 000 species of crustaceans. The horseshoe crab is a crustacean that bears some resemblance to the trilobite.

3.33.3

14 Which radioactive substance may be used to date plant and animal fossils? Could it be used to date fossils that are 100 000 years old?

15 What ages can the two forms of radioactive accurately date?

Geological time scale 16 Write the following eras in order, starting with the

most recent.Palaeozoic Cenozoic Archaeozoic Azoic

17 Which periods make up the Mesozoic era?

18 In which period did:a reptiles evolveb Tyrannosaurus livec land plants appeard bacteria evolve from a ‘chemical soup’ in the oceanse birds appearf plant-eating dinosaurs have their heydayg fish appear on Earthh sea plants appeari flying reptiles first existj dinosaurs last live?

Thinking questions

19 How can trees be used to trace back time?

20 True or false? Copy the true statements in the following list into your workbook. Rewrite any incorrect statements to make them true.a A dinosaur footprint is not a fossil.b Minerals may replace the shell or bone of an animal

to make a fossil.


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b

a

Fig 3.3.10

25 Compare the fossil layers in Figure 3.3.11 that were found in three different locations of Australia.a Which fossil was common to each location?b Identify which rock layers are of the same age.c Which fossil appears to be the oldest?

26 Copy and complete the table below.

27 Construct a scale timeline of the first three eras and the periods they contain. Use arrows to indicate the appearance of humans and the reign of the dinosaurs.

28 Why would it be difficult to extend the timeline to include the Precambrian era?

Period Span (millions of years)

Quaternary 2

Tertiary 63

c Soft-bodied animals are less likely to form fossils than animals with shells or skeletons.

d Fossils are found only under oceans or other bodies of water.

e Generally speaking, lower layers of rock in a region contain older fossils.

f Fossils of complete animals do not exist.

21 How can rock containing fossils of sea life come to be in a desert or inland area far from the ocean?

22 In the year 79 AD, Mount Vesuvius erupted, burying the cities of Herculaneum and Pompeii under molten rock and mud flows. Lava hardened around the human victims, leaving human-shaped spaces which were later discovered. Explain how models were made of the victims.

Analysis questions

23 How old would the Earth be right now if it was formed in 4004 BCE?

24 What may have happened long ago that produced the tracks in Figure 3.3.10?

1

2

3

4

5

6

7

8

9

10

a

b

c

d

e

f

Location x Location y Location z

Fig 3.3.11

FossilsFossils


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at workSurfing

Companion WebsiteFind out how Australia has changed over 110 million years by connecting to the Science Dimensions 2 Companion Website at www.pearsoned.com.au/schools, selecting Chapter 3 and clicking on the Web Destinations button.

Researching megafaunaSurf your available resources (textbooks, encyclopaedias, Internet, etc.) to find details about some of the amazing giant animals, such as the diprotodon and the giant short-faced kangaroo, that roamed Australia between 40 000 and 1 600 000 years ago. Find:

• what other mega fauna existed• the environment in which they lived• their likely food sources• the theories explaining their extinction.

3.3 SCIENCEPresent your work in one of the following ways:

• a PowerPoint presentation• an interview with a diprotodon or giant short-

faced kangaroo• a rap song about a diprotodon or giant short-

faced kangaroo• a poster• a Word document with hyperlinks to various websites.

Reviewing

Ice AgeWatch the movie Ice Age and prepare a film review about it. In your review you must:

• give details about its length, leading actors, director, producer, studio and year of production

• list the types of animals in it• describe what happened in the end• assess how realistic the portrayals of the animals and

the conditions are• assess how accurate the science is in the film• suggest improvements to the film to make it more

accurate.

Present your review in one of the following ways:

• an interview with the director, chief animator or the palaeontologist advising the director

• a segment for a TV program such as ET, At the Movies or The Movie Show

• a single-page spread for an entertainment magazine or for a movie guide such as The Age Green Guide or TV Week.

Profiling

PalaeontologistsPrepare a profile of a famous palaeontologist such as Mary Anning, Edward Drinker Cope, Othniel Charles Marsh or current-day dinosaur hunters such as Patricia Vickers-Rich.

Present your work in one of the following forms:

• an interview with the palaeontologist for TV or a newspaper

• a role play or videoed segment for This Is Your Life• a written biography.

Constructing

TimelineMake a timeline of the history of the Earth condensed into a year. Indicate key events such as the emergence of humans and the ages of the trilobites and the dinosaurs.

3.33.3

Fig 3.3.12Diprotodon

Fig 3.3.13The giant short-faced kangaroo grew to 3 metres and up to 300 kilograms.



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[ Practical activities ]

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IT Investigating fossilsYou will needAccess to a fossils kit

What to do 1 Select a fossil and draw it as accurately as you can.

2 Underneath your drawing, write its name, the period and era it comes from and a brief description of what it is (animal, plant, fern, etc.).

Prac 1 Unit 3.3

3 Identify what type of fossil it is (bone, shell, mould or cast, footprint, carbonised, etc.).

4 Repeat for the other specimens.

Question

Construct a timeline of the fossils you investigated.

Questions

1 Plot a graph showing the number of ‘uranium atoms’ left after each toss. Draw a smooth curve like the one in Figure 3.3.14 through the middle of the group of plotted points. This is called a curve of best fit.

Prac 2 Unit 3.3

‘Radioactive’ cubesYou will needFifty or more small wooden cubes, with one face marked (e.g. with a dot), a cup, graph paper

What to do 1 Make sure one face of each cube has a distinctive mark

(e.g. a dot).

2 Imagine each cube represents an atom of radioactive uranium, the atoms of which emit invisible particles as they change into lead. Shake the ‘uranium’ cubes in a cup and tip them carefully onto a desk.

3 Cubes that land with the marked face uppermost are said to have ‘decayed’ into lead. Remove these from the pile and put them to one side. Count how many ‘uranium’ cubes are left by subtracting the number of ‘lead’ cubes that were removed.

3 Place your results in a table like the one below.

Number of ‘throws’

Number of ‘lead’ cubes

Number of ‘uranium’ cubes = 50–‘lead’ cubes

At the start 0 50

1

2

3

4 Collect the remaining ‘uranium’ cubes and repeat steps 2 and 3 until no ‘uranium’ cubes remain.

2 Use your curve of best fit to find the number of tosses taken for the original amount of ‘uranium’ to halve (this would be 25 cubes if you started with 50). This is called its half-life.

3 Compare the half-life for your experiment with that obtained by other groups.

4 Research what the actual half-life of real radioactive uranium is.

Number of tosses

Num

ber o

f ‘at

oms’

rem

aini

ng

Fig 3.3.14

FossilsFossils

3.3


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Tyrannosaurus, Brachiosaurus … we have all seen enough films to know that they are dinosaurs. Although the word ‘dinosaur’ means ‘terrible lizard’, some were gentle giants, eating only plants. Others were about the same size as a rabbit. Although films sometimes show otherwise, humans appeared on Earth long after the dinosaurs became extinct.

Clues from the pastFossils supply scientists with a surprising amount of information about the different types of dinosaurs:• The distance between

footprints can be compared with modern animals allowing scientists to estimate their speed.

• The approximate weight of a dinosaur can be found from the depth of a footprint.

Fig 3.4.2 These dinosaur footprints were found in Winton, Queensland and have been dated at around 100 million years old.

• Series of parallel sets of tracks indicate that dinosaurs congregated in herds.

• The discovery of several groups of fossilised eggs in the one area indicates breeding colonies.

• The skull of a dinosaur provides clues about its diet. Long sharp teeth indicate a dinosaur was probably a meat-eater, while a front plate indicates the dinosaur was probably a herbivore, using the plate to crop plants.

Fig 3.4.1Dinosaur fossils have allowed scientists to construct detailed information about the

dinosaurs, how they lived, their breeding patterns, what they ate and who ate whom.

Homework book 3.4 Outrun a dinosaur

A dodo of a scientist!The English palaeontologist Richard Owen first used the name ‘dinosaurs’. In the early nineteenth century he was an expert in extinct animals such as the dodo and moa and strange living animals such as the echidna and platypus. He collected dead animals from the London Zoo and once stored a dead rhinoceros in his hallway! He was a cold and ambitious man who often persecuted other scientists or claimed their work as his. He did, however, begin the first modern museum, the Natural History

Museum in London.

Discovery of the dinosaurs

The bones of dinosaurs were first found in 1787,

but scientists thought they were bones from cows (big

ones) or other existing animals. No-one had ever thought about dinosaurs until Mary Anning made her discovery in 1812.

Gideon Algernon Mantell was an English doctor

who was also interested in fossils. In 1822, his wife

found a strange, large tooth in some rubble …

a dinosaur tooth. This and other bone discoveries led to the idea that an extinct

set of reptiles once roamed the Earth.

UNITUNIT

3.43.4


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>>>• Marks on bones show how

muscles were attached. By comparing these marks to those on bones of today’s animals, scientists can reconstruct the basic shape of a dinosaur.

• Coprolites are fossilised dinosaur droppings (faeces). They can give scientists information about the feeding habits of the dinosaur species they came from.

• The pelvis strength of fossilised dinosaur embryos or hatchlings indicate whether or not newborn dinosaurs were independent of their parents. Crocodiles and emus, for example, have strong and hard pelvises allowing them to walk immediately after birth independently of their parent. Other baby birds normally need to stay in their nests to allow their pelvises to harden, making them dependent on their parents for food.

Cold-or warm-blooded?Scientists are still not sure whether dinosaurs were cold-blooded or warm-blooded. Cold-blooded animals require energy from the sun to move and function fully. Reptiles are cold-blooded animals. Warm-blooded animals generate their own body heat and can function fully in hot and cold temperatures. The downside is that they need to eat more than cold-blooded animals.

Some evidence suggests that some dinosaurs were warm-blooded.• The density of blood vessels in some dinosaur bones

resembles that of warm-blooded birds of today.• The number of predators compared to prey

for today’s warm-blooded animal populations is known, and is similar to the ratio found in dinosaur fossils.

• Dinosaur fossils have been discovered at Dinosaur Cove in southern Victoria. Australia was then within the Antarctic Circle, suggesting that the dinosaurs were warm-blooded because they coped with the freezing or near-freezing conditions.

Dinosaur familiesScientists call the dinosaur family Dinosauria, which is divided into two main groups—saurischia (lizard-hipped) and ornithischia (bird-hipped), which in turn are divided into subgroups.

War of the dino-hunters

In 1889, dinosaur hunter Edward Drinker Cope was first to describe a plesiosaur. We know

this dinosaur today as a long-necked, short-tailed

dinosaur. Cope made an embarrassing error,

however. He had put the head at the wrong end, to construct a short-necked, long-tailed dinosaur. His

friend Charles Marsh pointed out the mistake. From then on Cope and Marsh were at war and their teams of diggers

would throw rocks at each other it they were working

in the same area.

Fig 3.4.3 This fossilised duck-bill dinosaur hatchling was discovered with hundreds of other dinosaur eggs and babies—evidence that duck-bill dinosaurs used communal nesting grounds.

Homework book 3.5 Dino discovery

Prac 2 p. 82

Prac 1 p. 81

pubis

pubis

bird-hipped dinosaurlizard-hipped dinosaur

Fig 3.4.4 Dinosaurs are classified according to hip type.

DinosaursDinosaurs

Fossilised puke!Dinosaurs have left behind

their skeletons and their fossilised faeces (coprolites)

and scientists have even found fossilised dinosaur

vomit in a quarry in England! About 160 million years ago,

a sea-going Ichthyosaur (something like a big dolphin

with a pointy snout and sharp teeth) threw up after a big meal of shellfish. It

could not digest the shells so it vomited them up, the shells bearing distinctive marks from the acid in the Ichthyosaur’s stomach. The sperm whale of today does

something very similar: it vomits up the beaks of

squids that it cannot digest.


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Dinosaur classification chartFig 3.4.5

3.43.4

CeratopiansHorned

DINOSAURS (DINOSAURIA)

Lizard-hipped (saurischia)

ProsauropodsEarly plant eaters

SauropodsLong-necked browsers

Therapods

DeinonychosaursTerrible clawed

CarnosaursLarge carnivorous

CoelurosaursSmall carnivorous

Bird-hipped (ornithischia)

StegosaursPlated

Ankylosaursand

NodosaursArmoured

OrnithipodsBird footed

HadrosaursDuck billed

PachycephalosaursThick headed

A B

C D E

F

G

I J

H

A Prosauropod means ‘before sauropod’. Massospondylus lived 194–205 million years ago (or mya for short) and was a 5 metre long prosauropod whose name means ‘massive vertebra’. It probably walked on all fours most of the time, but was able to rear up on its hind legs to reach high growing plants.

B Apatosaurus (150–156 mya), formerly known as Brontosaurus, was a huge, 20 metre long sauropod with a long neck and tail, which it may have used to lash out at attackers. Despite having bones with a honeycomb structure to reduce weight, Apatosaurus weighed around 25 tonnes. Having such a small head for so big a creature probably meant that Apatosaurus had to eat continuously to get enought energy to power its large body.

C Deinonychus (113 mya) was a 3 metre long, 60 kilogram deinonychosaur (‘terrible claw’). It possessed saw-edged teeth, sharp claws on its hands and, on the second toe of each foot, even more deadly, large sickle-shaped claws which could swivel to slash prey.

The fossilised remains of three were found with one much larger, plant-eating dinosaur, suggesting that Deinoinychus hunted in packs.

D Allosaurus (130–156 mya) was probably one of the biggest meat-eating carnosaurs before Tyrannosaurus came along 50 million years later. Fossil evidence suggests that the 2 tonne, 11 metre long Allosaurus also hunted in packs.

E Coelophysis (225 mya) was a small, 3 m long carnivorous dinosaur weighing about

30 kilograms, with hollow bones. It walked on its two hind legs and hunted in packs. One fossil discovery indicated that it may have eaten its young (probably when food was scarce).

F Stegosaurus (150 mya) is the most well-known of the Stegosaur family of dinosaurs. It measured 9 metres in length and weighed around 2 tonnes. Evidence of networks of blood vessels in the plates from Stegosaurus’s back suggests that the animal may have used these to help control its temperature. By allowing the Sun’s rays to hit the larger side area of the fins it could quickly warm blood flowing through the vessels. When it needed to lose heat, Stegosaurus could have stood with its back to the Sun, preventing rays from hitting the larger surfaces of its plates.

G Armoured dinosaurs consisted of ankylosaurs who had heavy clubs at the end of their tails, and the more primitive nodosaurs which had no clubs, but were protected by longer spikes protruding from their sides. Fossil discoveries of Euoplocephalus (73 mya), a 7 metre long, 2 tonne dinosaur, have been of single animals only, suggesting it lived a solitary existence. Its tank-like armour even extended to bony shutters to protect its eyes. Predators would probably have attempted to turn such a dinosaur over and attack its soft underbelly.

H Triceratops, at 10 metres long, was the largest of the ceratopians, who had distinctive frills and horns which served as a warning to other dinosaurs. Marks in the cheek bones of

such animals are a clue that these creatures used their horns fighting against each other. One side of the crown of Triceratops’s teeth was protected by enamel, while the other side was not, with the result that one side wore down faster than the other—in other words, Triceratops had self-sharpening teeth!

I Hadrosaurs such as Parasaurolophous are distinctive because of their head crests containing nasal cavities. the crests are made of hollow bone and may have been used to attract mates or produce trumpeting sounds.

J Pachycephalosaurus was a 4.6 metre long, thick-headed dinosaur.

The dome at the top of its skull was up to 25 centimetres thick and may have been used by competing males as a battering ram during the mating season. Large olfactory lobes in the brain indicate Pachycephalosaurus had a keen sense of smell, which it could have used to avoid danger, rather than attempt to head-butt its way out of trouble.

I’ll rip your guts out!

Dromaeosaurs were a group of carnivorous

dinosaurs that all had retractable claws on their second toe

and a special kicking muscle on their thighs. They would kick and

slash out at their prey, disembowelling them

or cutting them into bits.


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Mega dust stormsVast amounts of ash and gases from erupting volcanoes may have spread around the Earth, lowering temperatures and blocking out sunlight. Many plants would have died, causing plant-eating dinosaurs to die of starvation. Carnivorous dinosaurs would then lose their food supply. Smaller animals such as mammals would have been able to survive by eating seeds, nuts and dead plant material until the skies cleared and plants began to grow again.

The most popular current extinction theory is that Earth was blanketed by dust thrown up when it was hit by a large asteroid. A thin layer of iridium appears in layers of rock deposited around 65 million years ago—the time the dinosaurs disappeared. Iridium is often found in asteroids and would have been spread worldwide if an asteroid hit Earth. A massive asteroid crater was discovered in 1991 at Chicxulub in the Yucatan Peninsula in Mexico, giving further support to this theory.

Extinction theoriesThe dinosaurs did not all die out at once. There are several theories about why they died out, some theories being more likely than others.

Food supplyFood supply may have run out because:• the carnivorous meat-

eating dinosaurs ate all the herbivorous plant-eaters

• the plant-eaters exhausted their food supply and died out, leaving the carnivores without food

• the new types of flowering plants that appeared in the Cretaceous period competed with existing plants, leaving too few for dinosaur consumption

• the new plants were indigestible by the dinosaurs or poisoned them.

DiseaseThe dinosaurs may have been killed off by a virus or bacteria that did not affect other animals. In such a diverse group of dinosaurs, though, some species could be expected to be immune or to develop resistance to the disease, leaving at least one dinosaur species on Earth.

Climate changeThe climate may have cooled significantly due to continental drift, mountain formation, changes in sea levels or changes in solar activity. If cold-blooded, the dinosaurs would have:• become very sluggish• found it harder to catch food• found it difficult to protect themselves or their eggs• may have only produced baby dinosaurs of one sex.

In contrast, the smaller warm-blooded mammals and birds would cope with the cold and would take advantage of the slow-moving dinosaurs, eating their eggs.

A change in temperature may have caused all baby dinosaurs to be one sex, leading to extinction. Eggs laid by present-day crocodiles develop into all males or all females depending on temperature.

Is this what ended the reign of the dinosaurs?Fig 3.4.6

Stomach stonesArchaeologists have

occasionally found piles of smooth stones among the rib bones of dinosaur fossils. It seems that some

dinosaurs deliberately swallowed carefully chosen

stones that could roll around in the gut helping to grind food and aid the

digestive process. The dinosaur would regurgitate them and seek new ones when the stones became

too small. These stones are called gastroliths—can

you suggest why?

DinosaursDinosaurs

The biggest dinoBrontosaurus (now

known as Apatosaurus), Supersaurus and

Ultrasaurus were big, but nothing compared to some

others. Seismosaurus, meaning ‘earthquake

lizard’ was 34 metres long. Agentinosaurus was a

35-metre-long, 60-tonne plant-eating monster

that weighed the same as ten African elephants. Sauroposeidon stood 18 metres high, as high as a four-storey building, and

had a neck 12 metres long.


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Aussie dinosaursThe 7-metre-long dinosaur Muttaburrasaurus lived in the area of Australia and was a relative of the Iguanadon. The bones of Qantassaurus were recently found near Inverloch in Victoria by Monash University palaeontologist Dr Pat Vickers-Rich and her team. Qantassaurus was a small, 1-metre-tall dinosaur weighing up to 40 kilograms. It was named after the Australian airline as thanks for assisting palaeontologists in transporting their many dinosaur

fossils over many years.MEXICO

USA

Gulf of Mexico

Caribbean Sea

CUBAYucatanPeninsula

impact site

high iridiumconcentration

Fig 3.4.7 The Chicxulub crater is buried deep under rocks 65 million years old and lies partly under the sea. Geologists found evidence of high temperature and pressure in the region by sinking bore holes 500 metres deep.

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Clues from the past 1 List eight ways scientists get information about dinosaurs.

Cold-blooded or warm-blooded? 2 Give an advantage of being:

a cold-blooded b warm-blooded.

3 List the evidence that suggests that dinosaurs may have been warm-blooded.

Dinosaur families 4 What feature is used to classify dinosaurs?

5 Give the common and scientific names of the two main groups of dinosaurs.

6 Which type of dinosaurs are:a armoured b small and carnivorous?

Extinction theories 7 How could volcanoes kill off all the dinosaurs?

8 Mammals are very small. How could they have killed off the much bigger dinosaurs?

9 List four ways food supply may have killed off the dinosaurs.

10 What evidence supports the theory that the dinosaurs were killed by an asteroid?

Thinking questions

11 Copy the true statements in the following list into your workbook. Rewrite any incorrect statements to make them true.a Dinosaurs were all cold-blooded.b A coprolite is a dinosaur egg.c Qantassaurus was a flying dinosaur.d Carnivorous dinosaurs depended on plant-eating

dinosaurs for food.

12 What clues might each of the following give about dinosaurs?a footprint depthb parallel tracksc several groups of eggs in the one aread fossilised droppingse pelvis strength of a baby dinosaur fossil

13 Suggest where each of the following dinosaurs were discovered.a Austrosaurusb Argentinosaurusc Indosaurus

14 Of what use is the large tail of the big two-legged dinosaurs such as Tyrannosaurus?

15 Match a dinosaur type to a description.

Dinosaur types: carnosaur, stegosaur, hadrosaur, sauropod, ceratopian

Descriptions: long-necked, duck-billed, large carnivorous, horned, plated

16 Give each of the dinosaur extinction theories a rating out of ten, with higher scores for the more likely causes, in your opinion. Give a reason for your rating in each case.

17 What do you think happened to the very large asteroids that have hit the Earth and caused craters? Why aren’t they still sitting in the craters? >>

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Analysis questions

18 Draw a scale diagram comparing the sizes of a person and an Apatosaurus.

19 If a Tyrannosaurus could run at 40 kilometres per hour, would it be able to outrun a person sprinting?

20 What subgroup of dinosaur do each of the following belong to?

UN

IT

at workSurfing

Researching dinosaursSurf your available resources (textbooks, encyclopaedias, Internet, etc.) to prepare profiles on four different dinosaurs. Provide information about things such as:

• the type of dinosaur • its length and weight• what its name means • its diet or prey• when it lived • its lifestyle.• where it lived


• a PowerPoint presentation• a Word document• a poster.

Researching evolution of the dinosaursSurf your available resources (textbooks, encyclopaedias, Internet, etc.) to investigate the evolution of dinosaurs and their relationship to modern birds and reptiles.

3.4 SCIENCE

PentaceratopsFig 3.4.9HypacrosaurusFig 3.4.12

TyrannosaurusFig 3.4.10

a

b

c

d

e

>>

DinosaursDinosaurs

VelociraptorFig 3.4.8

PachyrhinosaurusFig 3.4.11


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UN

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NIT

[ Practical activities ]3.4

UN

IT Learning from skeletons

Prac 1 Unit 3.4

3 Include the following on your diagram:• whether the eyes point forwards (as in a cat)

or sideways (as in a rabbit)• the type of teeth it has (incisors, canine,

molars, etc.)• whether it has claws or not.

You will needAccess to a variety of skeletons, skulls or clean bones (e.g. human, cat, rabbit, sheep)

What to do 1 Select a skeleton, skull or bone and accurately draw it.

2 Measure or estimate its dimensions.>>

a

b

Fig 3.4.14

Back in timeYou have been transported back in time to one of the periods of dinosaurs, and your time machine is programmed to return you to the present day only after a week in the Cretaceous period. Write a diary of how you survive the week.

Present your work as a written document or Word document.

Analysing

SkullsTrace the broken skulls shown in Figure 3.4.14 into your workbook.

1 Which skull do you think came from a carnivorous animal and which from a herbivorous animal? Explain your choices.

2 On your diagram, sketch what you think the skulls originally looked like. Include the likely shape of their front teeth and the orientation (front- or side-facing) of the eyes.

at workSCIENCE>>

Present your work as a ‘Go to’ classification key that can be used to identify types of dinosaurs.

Researching dinosaur huntersSurf your available resources (textbooks, encyclopaedias, Internet, etc.) to find out:

• how British doctor Gideon Mantell came to name a type of dinosaur called Iguanadon in 1822

• who discovered the famous Tyrannosaurus skeleton named Sue. Why was she the subject of a legal battle? Why do archaeologists think the specimen is female?

Present your work as an interview with the hunter.

Imagining

Dinosaurs evolvingImagine that dinosaurs didn’t die out. How would they have evolved over the last 650 million years? Would they still be the dominant life form on Earth? What effect may they have had on the evolution of other species, including humans?


• a model, drawing or painting of your ‘new’ dinosaur

• a written or drawn description of how a city would now look

• a science-fiction story. Fig 3.4.13 Could dinosaurs

have evolved into something like this?

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Making a dinosaur fossilYou will need

5 Mix up a thick plaster paste, fill the impression with it and allow it to dry.

6 Remove the cast of the ‘fossil’.

Questions

1 What would replace the Plasticine and plaster mix when a real fossil was made?

2 You have actually made two types of artificial fossil. Describe each one.

3 Give an example of something likely to have made each type of fossil.

Clay or Plasticine (to make a mould), pin, probe or blunt pencil, tracing paper or photocopy of the skeleton below, rolling pin or piece of dowel, cardboard or shoe box lid, plaster mix

What to do 1 Trace the skeleton shown in Figure 3.4.15.

2 Roll out a layer of Plasticine about half a centimetre thick, large enough for a copy of the skeleton.

3 Transfer a copy of the skeleton to the Plasticine by pushing a pin through the copy at key points to mark the shape and use a probe to form an impression of the skeleton.

4 Place the Plasticine in a shallow cardboard tray or shoe box lid that is at least 3 cm deep.

Prac 2 Unit 3.4

Fig 3.4.15

2 Suggest what type of teeth would benefit a carnivore and what would benefit a herbivore.

3 What would you expect the foot of a carnivore to be like?

4 Repeat for the other specimens.

Questions

1 Carnivores generally have front-facing eyes and herbivores side-facing eyes. Suggest why.

DinosaursDinosaurs


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Chapter review

[ Thinking questions ] 11 A particular mineral has a hardness on Mohs’ scale

of 6.5. Name a mineral it would:a be able to scratchb not be able to scratch.

12 Which element may be extracted from chalcopyrite?

13 Put the following stages of fossil formation in order from first to last.

movement in Earth’s crust lifts layers of rock

animal dies

weathering breaks down exposed rock

animal covered by sediment

14 What type of animals are more likely to form fossils?

15 Skeletons of a Protoceratops and a Velociraptor were excavated by archaeologists above some fossilised eggs. The Velociraptor’s chest was crushed, and it was gripping the Protoceratops by the neck. Suggest what might have happened in the past to produce this scene.

[ Summary questions ] 1 What is the difference between:

a a rock and a mineralb a crystal and a habitc pigment and streakd rock and ore?

2 Place the following in order from hardest to softest.calcitequartzcorundumtopaz

3 Match each rock type to a description.

Rock types: sedimentary, metamorphic, igneous

Descriptions: formed from molten material, made from broken down particles compressed into layers, made from other rocks changed by heat and pressure.

4 Classify the following as sedimentary, igneous or metamorphic.a shaleb sandstonec granited limestonee conglomeratef gneissg basalt

5 Draw a simplified diagram of the rock cycle.

6 Give a use of each major type of rock.

7 What do scientists measure to tell the approximate age of a rock?

8 In which eras were the following periods?a Silurianb Cambrianc Tertiaryd Jurassic

9 Name a life form that existed in each of the following times.a Devonianb Archaeozoicc Quaternary

10 List three possible reasons why dinosaurs became extinct.

Homework book 3.6 Geology crossword

Homework book 3.7 Sci-words


3 geology · rocks 13 copy and complete: _____ are the building blocks of rocks. 14 clay and sand...

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