Presenting the 'big ideas' of science: Earth science ...

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The ‘big ideas’ of Earth science

Presenting the ‘big ideas’ of science: Earth science examples Chris King The ‘big ideas’ of science are best understood as rounded ‘explanatory stories’. An example of an ‘explanatory Earth story’ on plate tectonics is described in detail and others are outlined.

Revision of the National Curriculum for Science In the current debate about future revisions of the National Curriculum for Science (NCS) in England and Wales, two of the documents that have already influenced the Curriculum 2000 revision and so are likely to have continuing influence in the future are: ■ the Association for Science Education (ASE) document Science education for the year 2000 and beyond (ASE, 1998) that resulted from wide consultation within the science education community (to which the Earth Science Teachers’Association contributed – Thompson, 1996) and, ■ the document, Beyond 2000: science education for the future (Millar and Osborne, 1998) that was ABSTRACT Future revisions of the National Curriculum for Science are likely to focus on providing a scientific understanding of the world for all pupils. In the revised curriculum, the ‘big ideas’ of science would best be considered as a series of ‘explanatory stories’. Such stories would be specially prepared for teachers as succinct accounts of key areas of science that pull the interconnected ideas together into a narrative relevant to pupils. An example of an ‘explanatory Earth story’ on plate tectonics is detailed to show how such a ‘story’ can be developed in an Earth science context, and five others are given in outline. In a further article one of these five stories will be given in detail and strategies and activities for presenting it in the most effective way will be presented.

produced as a result of a series of seminar discussions supported by the Nuffield Foundation. Both these documents argue for a science curriculum that would give all children a basic foundation of scientific understanding to prepare them for life in the scientific and technological world of the future (educating them in ‘scientific literacy’ as described in the Beyond 2000 document). Both documents also argue that the ‘big ideas’ of the science curriculum should be presented as ‘explanatory stories’. The ASE document concludes: ‘A number of the key scientific ideas benefit from being developed through a storyline approach’ (ASE, 1998). Beyond 2000 argues: ‘Our proposal is that science education should make much greater use of one of the world’s most powerful and pervasive ways of communicating ideas – the narrative form – by recognising that its central aim is to present a series of ‘explanatory stories’ (Millar and Osborne, 1998: 13).

The ‘explanatory stories’ approach Millar and Osborne (1998: 13) see ‘the heart of the cultural contribution of science as a set of major ideas’ and recommend that these should be presented as a series of ‘explanatory stories’. These are accounts that have broad features which interest and engage pupils and are able to communicate the ideas in a way that makes them coherent, memorable and meaningful. The ‘explanatory stories’ are not fiction, but use the narrative form to present the ideas as a rounded whole.

School Science Review, December 2001, 83(303)

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The stories (pp. 13–14): ■ emphasise that understanding is not of single propositions or concepts, but of interrelated sets of ideas that provide a framework for understanding; ■ help to ensure that the central ideas of the curriculum are not obscured by the weight of detail, so that both teachers and pupils can see clearly where the ideas are leading; ■ portray the sort of understanding that one would wish young people to develop through studying the science curriculum. The examples that Millar and Osborne (1998) provide (‘The particle model of chemical reactions’ and ‘The Earth and beyond’, pp. 14–17) are written at a level that teachers new to the subject area and able pupils would understand. The document does not specify how the stories should be used but they are presented as a framework through which teachers could develop in pupils a holistic understanding of the ‘big idea’. The ‘explanatory stories’ approach promoted by Beyond 2000 was developed over several years. An initial impetus came from a report called ‘Children and teachers talking science’ (Ogborn, Brosnan and Hann, 1992), which was based on a paper entitled ‘Describing explanation’ (Ogborn, 1991). The ideas in these publications were built upon by Arnold and Millar (1996) in ‘Learning the scientific “story”: a case study in the teaching and learning of elementary thermodynamics’. The approach was further discussed by Millar (1996: 13) in ‘Towards a science curriculum for public understanding’in which he argued that there are a number of ‘powerful models’ at the heart of science that provide explanations for natural phenomena. He described these explanations as a ‘story’ or ‘mental model’ that provides a means of thinking about what is going on. Meanwhile Osborne (personal communication, October 2000) has prepared an account of his understanding of the term ‘explanatory stories’. He argues that an effective narrative will begin in a context that is relevant and accessible to the hearer and hopefully imbues the story with awe and wonder. Normal narrative devices are used to give the story interest and impact, keeping the use of scientific jargon to a minimum. He quotes research indicating that children who had been exposed to such stories remembered the content better than those who had been taught using ordinary scientific texts. He concludes that ‘approaches that give pre-eminence

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to the affective components of wonder, joy and fascination, such as those found in popular science, are worthy of serious examination, and are better suited to the needs of some, if not the majority’. The development of the idea of ‘explanatory stories’ in this context should not be confused with historical stories of scientists and their discoveries, as discussed by Krieger (1992), Martin and Brouwer (1993) and Solomon (1993). Such historical stories are accounts of how scientific discoveries were made and Millar and Osborne would regard these as ‘stories about the story’ (personal communication, October 2000). The use of narrative and the importance of stories has also been discussed in relation to other subject areas, but with a different meaning as well. In the context of geography (see McPartland, 1998) and history (see Arthur and Phillips, 2000), the ‘stories’ being discussed are either historical accounts, as above, or primary sources, stories that were written at the time, describing events and reactions to events. In summary the ‘explanatory stories’ approach of Millar and Osborne (1998) is based on Millar’s ‘powerful models’ that see science as the development of a number of big ideas. For each big idea, an ‘explanatory story’ is prepared that encapsulates how the big idea developed to our present scientific understanding of it, and emphasises the key components of the big idea and their importance for humanity today. The two exemplar ‘explanatory stories’ that appear in Beyond 2000 have therefore been specially written, are relatively short (a few hundred words) and signal key concepts involved in the ‘powerful model’ being exemplified. They begin in an accessible way, are written clearly and simply, and attempt to explain the scientific understanding behind each of the concepts involved. It is envisaged that a teacher would use the story as the focus for that part of the curriculum. The teacher would seek to develop an understanding in pupils of the whole story and its interlinking concepts through a number of approaches, including the use of practical work, and an emphasis on the scientific background to the story and the importance it has in the lives of people today. By selecting just a few pivotal ‘stories’, the overall content of the science curriculum would be reduced, thus enabling a closer focus on the development of the big ideas and their importance. Following publication of Beyond 2000, the use of ‘explanatory stories’ in the science curriculum has

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been further developed in the preparation of an ASlevel examination syllabus (Advanced Subsidiary GCE syllabus, aimed at 16–17 year-old students) on ‘Science for public understanding’(AQA, 1999). This presents the content of the section entitled ‘Scientific explanations’ as a series of twelve explanatory stories. The syllabus is supported by a textbook: AS science for public understanding (Hunt and Millar, 2000). Although some of the documents cited above include in their lists of quintessential ‘explanatory stories’ one that relates to the Earth (e.g. Millar, 1996: 14, ‘Models of the evolution of the Earth’s surface (rock formation, plate tectonics)’ and Millar and Osborne, 1998: 18, ‘The formation and evolution of the Earth’), no ‘explanatory Earth stories’ have yet been prepared. Such coherent accounts should prove to be of real value to the large number of non-Earth science specialists currently teaching Earth science in the science curriculum in England and Wales. Research has shown that many of these teachers have a poor understanding of the Earth science they teach (King, 2000, 2001a,b).

Preparing explanatory Earth stories As described above, to fit the ‘explanatory story’ mould, each ‘explanatory Earth story’ should encapsulate the key components of a ‘big idea’ in a specially written narrative that is relevant and accessible to children. It should imbue the ‘big idea’ with appropriate awe and wonder, and provide fundamental scientific understanding in an easily digestible, coherent and lucid form. An ‘explanatory Earth story’ – A plate tectonic model for the Earth – has been prepared as a response to this challenge (see Box 1). This ‘big idea’ of plate tectonics was developed as recently as the 1960s and pulled together a range of previous ideas. It was first described by J. Tuzo Wilson (Wilson, 1965), but has been developed since that time.

Explanatory Earth stories for the whole science curriculum The ‘A plate tectonic model for the Earth’ explanatory story by no means covers the whole of the Earth science contribution to a broad, balanced and relevant science curriculum. Our future citizens need to be able to take a broad view from local to global scales of all the interacting cycles that affect our planet now, have


done so in the past and will shape our planet’s future. Such a broad view would be provided by stories covering the ‘big ideas’ in the following areas: ■ the Earth’s crust; ■ atmosphere and ocean; ■ time and life; ■ resources and sustainability; ■ Earth’s cycles. The forms that such stories might take are shown in Boxes 2 to 6. Each of the stories contains elements of the systems science approach that sees the science of the whole planet as a series of interconnected systems. The systems science approach (described by Mayer and Kumano, 1999) is becoming popular in the USA and a number of other countries and would be particularly highlighted in an explanatory story on ‘Earth’s cycles’.

Conclusion The ‘explanatory stories’ approach provides an effective means of bringing ‘big ideas’ to all pupils. Each ‘explanatory story’ takes a key area of science and presents the teacher with the interconnected ideas in a coherent, lucid and meaningful way. For such stories to be helpful to teachers they need to be succinct, easily digestible, begin at a level that will be accessible and relevant to pupils, and seek to highlight some of the awe and wonder of science. The list of stories chosen as part of a broad and balanced science curriculum that prepares pupils for life in our scientific and technologically based world will undoubtedly include some Earth stories. Two ‘explanatory Earth stories’ have been prepared to show how such stories can be developed in detail. One, ‘A plate tectonic model for the Earth’, is presented here and the second, ‘The dynamic Earth’s crust’ is the subject of a future article to be published in SSR, in which appropriate teaching strategies and activities for teaching the story are outlined. Further ‘explanatory Earth stories’ that would provide breadth, balance and relevance to the science curriculum, and give the sound foundation of environmental understanding crucial to those making environmental decisions in the future, include ‘stories’ on ‘atmosphere and ocean’, ‘time and life’, ‘resources and sustainability’ and ‘Earth’s cycles’. The last of these embraces the systems approach to science that is becoming popular in the USA and elsewhere.


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Box 1

A plate tectonic model for the Earth – an ‘explanatory Earth story’

If you could sit in space and study the Earth you might see some strange patterns through the swirls of cloud. Many of the mountains are found in long chains; islands are found in long curved chains; the coastline of South America fits the coast of Africa almost exactly. If you could probe beneath the oceans, more patterns would be revealed: there is a long ridge of mountains near the centres of most oceans and there are usually deep sea trenches near the island chains. These patterns and more can be explained by plate tectonics. Earthquakes are dangerous but their waves show what it is like below the surface. We find that the outer part of the Earth is made of a thin rigid sheet that we call the lithosphere, which is broken into pieces called plates. Beneath the lithosphere is a thin layer called the asthenosphere where earthquake waves are slowed down. The Earth is heated from within by the decay of radioactive materials and the asthenosphere is so hot that there are films of molten rock between the crystals. This slows the earthquake waves and also allows the mainly solid asthenosphere to flow. Slow convection currents in the asthenosphere carry the plates along with them. The earthquake waves show that the lithosphere is made of an upper part called the crust and a lower part called the mantle. The mantle continues through the asthenosphere to a depth of 2900 km. There the waves change suddenly as they go from the solid mantle into the liquid outer core. The core is mainly iron and its currents cause the Earth’s magnetic field. Another wave change 5100 km down marks the boundary between the liquid outer core and the solid inner core. Where plates of lithosphere are moved away from each other by convection currents that rise and flow outward, this causes ‘pull apart’ tensional forces at the surface. The lithosphere becomes hot and less dense so that it rises to form an oceanic ridge. As the ridge is pulled apart, the middle section slides down along steep fractures called normal faults, making a central valley. Sudden movements of the faults cause earthquakes. Under the ridge, partly molten ironrich rock collects together and rises as magma. As the plates are pulled apart, magma rises

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quietly into the fractures and solidifies to form new oceanic lithosphere. The solidifying magma takes on the magnetic field of the Earth. The Earth’s magnetic field has reversed many times in the past and the oceanic lithosphere contains a continuous record of this, as a series of zones of normal and reversed magnetism. The ridges are offset by large transform faults where the plates slide past one another producing earthquakes. Where plates are moved towards one another, one of the plates is carried down or subducted into the mantle, producing an oceanic trench and a steadily deepening zone of earthquakes. The water carried down with the subducted plate reduces the melting point of the surrounding rocks so that they partially melt, the silica-rich material melting first. This silica-rich magma is viscous and so causes explosive volcanic eruptions when it reaches the surface. In ocean areas the volcanoes form curved chains of volcanic islands and these can be dangerous places to live. Some plates carry continents and if a plate is subducted beneath a continent, a trench, volcanoes and earthquakes are formed, but the base of the continent is partially melted as well, producing magma very rich in silica and very viscous. This rarely reaches the surface but usually forms large igneous bodies that cool slowly, baking and metamorphosing the surrounding rock. If the silica-rich magma does reach the surface it forms highly explosive volcanoes. The two converging plates also crumple up the layered sediments and sedimentary rocks into mountain chains, causing compressional faulting, folding and metamorphism. If both plates carry continents, the huge forces involved in the collision form the highest mountain ranges on Earth as the continents are ‘welded’ together by the new mountain chain rocks. The new mountains are prone to dangerous earthquakes and landslides. Plate tectonic theory was first proposed in the 1960s and changed our scientific views of the Earth. It explains many of the Earth’s patterns and its activity, features and evolution, but still leaves unanswered questions. These have provoked further scientific study ever since.

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Box 2 The dynamic Earth’s crust – outline ■

How could the sand that forms sandstone cliffs be linked to the sand on a beach?

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Rocks contain clues on how they were formed and can tell us about life in the past.

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Box 4 Time and life – outline Based on Concepts related to time, particularly geological time (Thompson, 1995).

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Flat-lying rocks are deformed by Earth forces during mountain-building.

How can the huge variety of life, from minute bacteria to great whales and from ancient dinosaurs to modern birds, be explained scientifically?

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Earth processes can be so intense in mountain-building that rocks are recrystallised or melted.

Events in the rock record can be placed in time sequence.

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The rock record shows a sequence of organisms preserved as fossils.

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Rock forming and deforming processes are linked in a dynamic cycle that relates to other key Earth cycles.

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The Theory of Evolution was proposed by Darwin to explain the sequence of fossils and the variety of life today.

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Evolution has a complex history of many radiations and extinctions.

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Some rocks (and thus the fossils they contain) can be dated by radioactive methods; they show evolution of life over millions of years.

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Today, humans influence the evolution of life as causers of extinction and through genetic modification.

Box 3 Atmosphere and ocean in balance – outline Based on Chemistry of the atmosphere (Lister, 2000), prepared from an article by Fleming (1998). ■

The changing weather outside the window is the atmosphere in action.

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The atmosphere and ocean change on time scales of seconds to millions of years.

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Their movement is driven mainly by energy from the Sun; tides are caused by the Moon.

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They probably originated from volcanic gases released early in Earth’s history but their chemical make-up changed over millions of years.

Box 5 Resources and sustainable development – outline ■

Why can we get valuable things from the ground in some areas and not in others?

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Earth has variety because elements and their compounds are not evenly distributed.

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Resources are natural concentrations of elements or compounds.

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Carbon dioxide dissolved in the oceans, became part of shelly marine organisms and eventually was ‘locked up’ in limestone deposits.

Concentration can be caused by chemical processes, by physical processes, by biological processes, or by a combination of these.

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Ozone formed from oxygen in the upper atmosphere; it absorbs harmful u-v radiation allowing life on the Earth’s surface to exist.

Extraction of natural resources usually involves further concentration through technology.

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The balance of chemical compounds in the atmosphere and oceans is changed by human activity today, giving global environmental concerns.

Natural resources are normally being extracted very much faster than they are being formed.

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Future sustainability will involve a balanced combination of extraction that minimises environmental damage, of efficient use of resources, and of recycling.

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When plants evolved, photosynthesis absorbed carbon dioxide and released oxygen into the water and atmosphere.


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Box 6 Earth cycles and interactions – outline ■

When water in a saucepan boils, drips form on the lid and fall down into the liquid illustrating the water cycle.

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Cycling can be fast or slow; rate of cycling depends mainly on how long the products are stored in different parts of the cycle.

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Cycling processes are physical, chemical, biological or a combination of these.

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Natural cycles that particularly affect humans include the water, rock, carbon, and nitrogen cycles.

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The cycles interact.

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Cycles can have feedback loops that maintain products in balance.

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Humans strongly influence many Earth cycles.

The most effective ways of teaching each story will involve a wide range of activities in which practical

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and investigational work, both in the laboratory and outside in the field, will play a key role. Each of the activities should be linked directly to the relevant parts of the ‘story’ if it is to build broad understanding in pupils of the interconnections within the story. This is the approach illustrated in the coming article on ‘The dynamic Earth’s crust’. The strategies and activities outlined will be of particular value to those science teachers who have little Earth science in their own educational backgrounds but who are teaching NCS Earth science. Such approaches are exemplified by the interactive INSET workshops provided by the Earth Science Education Unit, described by King (2001a). It is therefore recommended that a future curriculum, aimed at preparing all pupils for life in our scientific and technological world, should include ‘explanatory Earth stories’ of the type outlined. This will enable them to become involved in the crucial environmental debates and decisions of the future on the basis of sound scientific knowledge and understanding.

Acknowledgements Preparation of the ‘explanatory Earth story’ given here in detail and the five others offered in outline has been greatly enhanced by discussions with Alastair Fleming and David Thompson at Keele. The detailed story was made more lucid and accessible through discussions with John Moran. I am very grateful for these contributions.

References Arnold, M. and Millar, R. (1996) Learning the scientific ‘story’: a case study in the teaching and learning of elementary thermodynamics. Science education, 80, 249–281. Arthur, J. and Phillips, R. (2000) Issues in history teaching. London: Routledge. AQA (1999) General Certificate of Education, Advanced Subsidiary: Science for public understanding. Manchester: Assessment and Qualifications Alliance. ASE’s Science Education 2000+ Task Group (1998) Science education for the year 2000 and beyond. Education in Science, 176, 17–20. Fleming, D. A. F. (1998) Teaching the evolution of the atmosphere at key stage 4. Teaching Earth Sciences, 23, 130–134. Hunt, A. and Millar, R. (2000) AS science for public understanding. Oxford: Heinemann. King, C. (2000) The Earth’s mantle is solid: teachers’ misconceptions about the Earth and plate tectonics. School Science Review, 82(298), 57–64.

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King, C. (2001a) Earth science teaching in England and Wales today – progress and challenges. Teaching Earth Sciences., in press. King, C. (2001b) The response of teachers to new content in a National Science Curriculum: the case of the Earthscience component. Science Education, in press. Krieger, M. H. (1992) Doing physics: how physicists take hold of the world. Bloomington: Indiana University Press. Lister, E. (2000) Chemistry now: Chemistry of the atmosphere. London: Royal Society of Chemistry. Martin, B. and Brouwer, W. (1993) Exploring personal science. Science Education, 77, 441–459. Mayer, V. J. and Kumano, Y. (1999) The role of system science in future school science curricula. Studies in Science Education, 34, 71–91. McPartland, M. (1998) The use of narrative in geography teaching. The Curriculum Journal, 9, 341–355. Millar, R. (1996) Towards a science curriculum for public understanding. School Science Review, 77(280), 7–18.

King Millar, R. and Osborne, J. ed. (1998) Beyond 2000: Science education for the future. London: King’s College, University of London. Ogborn, J. (1991) Describing explanation. ESPRIT II Basic research actions working group 6237: Children’s and teachers’ explanations. Technical paper number 1. Ogborn, J., Brosnan, T. and Hann, K. (1992) CHATTS Working paper 4. Explanation: a theoretical framework. London: Institute of Education, University of London.

The ‘big ideas’ of Earth science Solomon, J. (1993) Teaching science technology and society. Oxford: Oxford University Press. Thompson, D. B. (1995) Concepts related to time, particularly geological time: a PGCE self study unit. Keele University. Thompson, D. B. (1996) Science education for the 21st century – an ESTA response to the ASE debate. Teaching Earth Sciences, 21, 83–88. Wilson, J. T. (1965) A new class of faults and their bearing on continental drift. Nature, 207, 343–347.

Chris King is Science Education Lecturer: Earth Science, Department of Education, Keele University, Keele, Staffs ST5 5BG. E-mail: [email protected] Chris is the Director of the Earth Science Education Unit. This is administered from Keele University and provides free Earth science INSET across England and Wales to science departments in secondary schools, to meetings of science teachers and to teacher education institutions. Contact Chris for further details or refer to the ESEU website: www.earthscienceeducation.com


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