GEOLOGY STUDY GUIDE Module exam GL1 June 2004

IGNEOUS ROCKS AND THE ROCK CYCLE
Geology Department, GreenheadCollege, Huddersfield.
Your name .....……………………...... Date ...... ……………......
LEARNING TARGETS
margin notes
When you have completed this study guide, you will:
  • Understand the rock cycle
  • Know about how solar and geothermal energy drive the rock cycle
  • Recognise igneous and volcanic rocks and understand their texture and composition
  • Know about the two main types of volcanoes and their products
  • Have carried out group research and then given a class presentation
  • Know about the features of intrusive volcanism.

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
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






 / Go to Teaching Resources
vulcan.wr.usgs.gov/

volcano.und.nodak.edu



There are many other websites you could search.
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:
  1. Make a note of what evidence tells geoscientists that the earth is hot inside.
  2. How is the planet’s geothermal heat generated?
  3. How much does temperature change with depth?
  4. 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
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
ACTIVITY 3 : EXTRUSIVE VULCANISM
Margin notes / 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 betweenshield volcanoes and strato-volcanoes (which are the steep sided ones in IGR 1). For each, say:
  • 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: ……………………………..
ACTIVITY 4 : INTRUSIVE VOLCANISM
Margin notes / TASK 13 INTRUSIVE IGNEOUS FEATURES
Using any resources, write about the following intrusive features:
•dykes
•sills
•batholiths/stocks/plutons
For each one, you need to find out about:
•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 VolcanoesTape 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: GreenheadCollege Date:May 05

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