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GEOLOGY STUDY GUIDE
Module exam GL1 June 2004
IGNEOUS ROCKS AND THE ROCK CYCLE
Geology Department, Greenhead College, Huddersfield.
Your name .....…………………….................................................
Date .........……………...........
LEARNING TARGETS
margin notes
When you have completed this study guide, you will:
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Understand the rock cycle
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Know about how solar and geothermal energy drive the rock cycle
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Recognise igneous and volcanic rocks and understand their texture and
composition
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Know about the two main types of volcanoes and their products
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Have carried out group research and then given a class presentation
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Know about the features of intrusive volcanism.
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GEOLOGY STUDY GUIDE
Module exam GL1 June 2004
Resources
Here is a choice of resources to use. You do not need to look at them all but clearly the more you read the
better your knowledge of case studies will be. Tick the box once you have used the resource.
If you read a photocopied extract then highlight it to help you reread it for revision. If you make notes
from a video tape make sure that the notes are headed with the name of the tape so that you know the
source of your information.
IGR1
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IGR2
IGR3
IGR4
IGR5
IGR6
IGR7
IGR8
IGR9
IGR10
IGR11
IGR12
IGR13
IGR14
Understanding Geology David Webster p 31-41
Geoscience Edwards and King p 53-70
Geological Science by Andrew McLeish p 50-65
Recycling the Earth New Scientist Inside Science 17 January 1998
Table to show igneous rock compositions
Table to show igneous rock textures
Earthquest CD Rom
Table to describe and explain features of lavas and pyroclastic deposits
Presentation information
Video Inside Volcanoes Tape 1, 3, 4 ,20 23 mins
Library Video Earth and Life. Above the Volcano 30 mins
Library Bernard W. Pipkin Geology and the Environment Chap5
Library Video Earth Story Programme 3 Ring of Fire 50 mins
Library Video Earth Story Programme 4 Journey to the Centre of the Earth 50 mins
Websites
www.geolsoc.org.uk/ Go to Teaching Resources
vulcan.wr.usgs.gov/
www.geo.mtu.edu/~boris/ETNA_news.html
volcano.und.nodak.edu
www.science.ubc.ca/~geol202/igneous/igneous.html
www.science.ubc.ca/~geol202/rock_cycle/rockcycle.html
www.norvol.hi.is/
There are many other websites you could search.
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GEOLOGY STUDY GUIDE
Module exam GL1 June 2004
ACTIVITY 1 : THE ROCK CYCLE
Margin notes
TASK 1 EARTH’S HEAT AND ENERGY
Read IGR 2 p 33 section 2.6.1 The Temperature Rises. Answer these questions:
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4.
Make a note of what evidence tells geoscientists that the earth is hot inside.
How is the planet’s geothermal heat generated?
How much does temperature change with depth?
Give some examples and then explain what the term geothermal gradient
means.
TASK 2 HEAT TRANSFER
If heat is generated within the earth how is heat transferred to the surface?
Give an account in your own words using these words:
Convection, conduction, partial melting, asthenosphere, mantle flow
Draw diagrams if they help to explain the heat transfer processes.
Read IGR 4 for greater insight into this process.
TASK 3 THE ROCK CYCLE
Most of the earth’s surface is cold and the rocks are brittle. However the sun’s
energy drives processes which take place on the surface. The combination of
geothermal energy and solar energy causes geological changes on the surface and
inside the earth. All these processes are linked into each other by the rock cycle.
Using the rock cycle diagrams from IGR 1 p28 or IGR 2 p18-19 write an account
of how the rock cycle works.
TASK 4 ROCK CYCLE DIAGRAM
Choose which diagram you prefer from the textbooks and adapt it so you have a
good version to learn.
Use this box for notes
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GEOLOGY STUDY GUIDE
Module exam GL1 June 2004
ACTIVITY 2 : IGNEOUS ROCKS
Margin notes
TASK 5 IGNEOUS ROCK COMPOSITION
Define magma and lava.
Magmas can be divided into four groups on the basis of composition. These are
acid (silicic), intermediate, basic (mafic) and ultrabasic (ultramafic). How they
are formed depends on processes in the crust and mantle which we will study later.
Complete the table IGR 5 to show the mineral composition of each rock type.
TASK 6 TEXTURE AND COMPOSITION
You can now link texture and composition of igneous rocks by completing IGR 6
using the following rock names:
Dolerite, gabbro, basalt, granite, andesite, rhyolite, peridotite and obsidian
(pitchstone)
IGR 1 p 40 will help you although it does not include peridotite. Note the
grain(crystal) sizes of each rock texture.
Date of test on igneous rock compositions and textures……………………………
TASK 7 COOLING RATES OF MAGMAS
Magmas which crystallise deep in the crust because they have reached their melting
point have cooled slowly because the temperatures of the magma and the
surrounding country rock are roughly similar. They therefore have large crystals
because the crystals have time to grow as the magma cools slowly. Magmas
which reach the surface and cool as lavas have small crystals because they chill
rapidly in air or water. Magmas which cool at shallow depths in the crust have
medium-sized crystals.
Draw a labelled diagram linking depth in crust with crystal size.
TASK 8 CRYSTAL TEXTURE OF IGNEOUS ROCKS
Because crystals in magmas are able to cool slowly at depth they can grow good
crystal shapes. Well-shaped crystals which cooled first are called euhedral, while
crystals that have a poor shape are called subhedral and the crystals which formed
last of all and therefore filled in the spaces between the others have no regular
shape and are called anhedral.
Draw a magnified diagram to show crystal textures in a sample of Shap granite.
Phenocrysts are the large crystals which you will find easy to recognise. Use
labelling on your diagram to identify each separate mineral. Remember to add a
scale.
Shap granite is an example of porphyritic texture in igneous rocks. We will
discuss in class how the process of two-stage cooling in the crust produces a
porphyritic texture.
Use this box for notes
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GEOLOGY STUDY GUIDE
Module exam GL1 June 2004
ACTIVITY 3 :
Margin notes
EXTRUSIVE VULCANISM
TASK 9 SHIELD VOLCANOES AND STRATO-VOLCANOES
Acid and basic magmas produce different types of volcanoes because acid magmas
contain silicic minerals like quartz and feldspar which makes the lava sticky
(viscous) while basic magmas have mafic minerals which make the lavas runny.
In class we will draw diagrams linking rock composition with the two types of
volcanoes – shield and strato-volcanoes.
1. Take it in turns to use the IGR 7 Earthquest CD Rom to build a volcano.
2. Read IGR 1 p32 and IGR 2 p53-54 and make notes to show the difference
between shield volcanoes and strato-volcanoes (which are the steep sided ones in
IGR 1). For each, say:
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What igneous rocks each is made from
What type of eruptions occur to produce each volcano
How dangerous they could be to humans because of various hazards
Two examples of each type of volcano and where in the world it is found
If you want to draw diagrams make sure that you do not draw the sides too steeply.
Shield volcanoes have a slope of no more than 15o and strato–volcanoes no more
than 40o, with concave slopes rather than straight slopes. Why do strato-volcanoes
have concave slopes generally? Use a protractor.
TASK 10 FEATURES OF LAVAS AND PYROCLASTIC DEPOSITS
Use IGR 1 and IGR 2 to find out about these features and deposits – ropy lava,
blocky lava, flow-banded lava, pillow lava, vesicular lava, amygdaloidal lava,
flood basalts, columnar jointing, volcanic bombs and ashes and tuffs. Use IGR
8 to make notes to describe and explain the origin of each feature. Draw diagrams
to help you remember the features.
TASK 11 PRACTICAL
There are 4 main igneous rocks – granite, gabbro, dolerite, basalt – that you need
to be able to recognise in a practical.
Fill each practical sheet with a labelled pencil drawing to scale of a specimen of
each of these rocks. Note how hard the rock is, because of its crystalline nature.
Mention whether the texture is equigranular or porphyritic and if the crystal
shapes are euhedral, subhedral or anhedral.
If you can recognise by tests and observations any of the minerals in granite and
gabbro then label them, with reasons. Dolerite and basalt crystals are too small for
you to identify them even with a lens.
TASK 12 PRESENTATION
Your group will research volcanism in a chosen area and give a presentation to the
class. Full details are in IGR 9. There are many resources you can use for your
research so we will spend some time in lessons in groups researching and planning.
Date of presentation: ……………………………..
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GEOLOGY STUDY GUIDE
Module exam GL1 June 2004
ACTIVITY 4 : INTRUSIVE VOLCANISM
Margin notes
TASK 13 INTRUSIVE IGNEOUS FEATURES
Using any resources, write about the following intrusive features:
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dykes
sills
batholiths/stocks/plutons
For each one, you need to find out about:
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how it is formed
what rocks it may be made of
what landform it may produce after exposure at the surface and weathering
2 places where you could find each intrusion in the UK
TASK 14 VIDEO
Watch the video Inside Volcanoes Tape 1, 3, 4, 20 22 mins which covers the
extrusive vulcanism of Mount Etna and the intrusive volcanism seen in Scotland.
There are many other videos on volcanoes which you can borrow to watch at home.
TASK 15 GLOSSARY
This topic is full of new terms which need defining. Write a list with their
definitions and learn them.
Deadline for handing your glossary in: ………………………………………
TASK 16 EXAM QUESTION PACK
Complete the Igneous Rocks EQPs
Deadline: ……………………………………
TASK 17
REVIEW NOTES
You need to learn this topic now.
Review notes deadline: …………………………………………
Use this box for notes
ESTA GEOTREX The Geology Teachers Resource Exchange Contributor: Alison Quarterman Establishment: Greenhead College
Date:May 05
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