Science at key stage 3 (Year 8)
Unit 8H: The rock cycle
Section 5: b. Where do igneous rocks come from?
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Objectives |
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- to use first-hand and secondary sources of data to investigate differences between igneous rocks
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Activities |
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Outcomes |
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Children: |
- Present samples of granite and gabbro to pupils and ask them to suggest evidence for their origin as igneous rocks.
- Show pupils how to find the relative densities of the two rock samples using displacement and ask pupils what could cause the difference in their densities. Ask pupils to investigate the relative densities of other igneous rocks,
eg obsidian, basalt, and to use what they know about the difference in relative density to decide whether they are more like granite or gabbro.
- Where appropriate, present pupils with data about the relative density, mineral composition and chemical composition of gabbro and granite and help them to use the data to show that granite rocks are relatively silica rich and gabbroic rocks are relatively iron rich.
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- use data to assign igneous rocks to one of two main groups, dense iron-rich or less dense silica-rich
- show how relative density relates to composition of igneous rocks
- evaluate how well their data supports their conclusions
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Points to note |
- Data about location and type of volcano can be found on the internet at,
eg www.geo.mtu.edu/volcanoes/world.html or http://volcano.und.nodak.edu
- Extension: pupils could be asked to find out about specific volcanic eruptions and their effects on the local population and environment. Teachers will be aware that sensitivity is needed where pupils have relatives or friends living in volcanic areas.
- Extension: pupils could be asked to use secondary sources to locate where volcanoes with silica-rich rocks (continents) and volcanoes with iron-rich rocks (oceans) are found. They could then identify the location of explosive volcanoes (with violent and generally unpredictable eruptions producing ash and pumice, not lava),
eg Montserrat and moderate volcanoes (with streaming lava flows and frequent eruptions producing basalt lavas, sometimes with gas bubbles),
eg Hawaii. Discuss how strongly the evidence supports the link between the chemical composition of magma and the types of volcanic activity.
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This unit is divided into sections. Each section contains a sequence of
activities with related objectives and outcomes. You can view this unit by
moving through the sections or print/download the whole unit.
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