Teachers

=Earth Sciences= Earth Science, as a topic in school science, is often linked to the rock cycle, materials and the differences between rock types. However, the history and context of the topic makes it ideally suited to teaching within a historical framework, emphasising the role of collaborative research, and of scientists building on previous research. It also allows students to be introduced to ideas such as paradigm shifts, major themes in scientific research such as uniformitarianism and forming hypotheses from empirical observation. The research and observations leading to the development of the rock cycle, build on each other, through time and via work by different scientists, in a very marked way, meaning that students' understanding of how science works can be developed. The paradigm shift away from catastrophism towards uniformitarianism and the subsequent use of fossils as a chronological tool can be used to introduce key concepts in scientific thought. The historical framework can be used to inform teaching activities, as learners are introduced to, and work through the research of early scientists, recreating the story of these discoveries. This becomes a scaffold from which teaching can hang.

// Key discoveries and scientific thought // [|Archbishop Usher](also known as Ussher) published work (1660 and 1654) concerning the age of the earth using biblical chronology. This was an early attempt to investigate the antiquity of the earth and human kind's place in this. This paved the way for researchers to begin to experiment, using the tools at their disposal, and to discuss issues such as chronology in an evidence-based context. Following this, [|Nicolaus Steno]used inductive reasoning based on empirical observation to forward the principles of stratigraphy in 1669. This is the corner-stone of chronology and of modern understanding of the rock cycle. Steno's observations led directly to the establishment of processes and ultimately to the uniformitarian assumption. Interestingly, Steno, as a Roman Catholic, and typically of the period, was a creationist, whose work is cited both by geologists discussing the move towards uniformitarianism and by young earth creationists. In 1778 Georges-Louis Leclerc, [|Comte de Buffon]experimented by making a small iron model of the earth and, based on the cooling rate, forwarded 75000 years as the age of the earth. This move towards empirical deduction based on experimentation paves the way for the application of a hypothetico-deductive approach to the subject. In 1785 James Hutton's // Theory of the Earth // was read to the Royal Society of Edinburgh. Hutton's work (later emphasisied by Lyell) laid out the theory of uniformitarianism which underpins work in establishing chronology, geological process, geography, archaeology and quaternary science, stating that as things happen now, so this can be applied to the past. This led to his discussion of the Rock Cycle in 1788. His rock cycle was seen as having 'no vestige of a beginning, no prospect of an end'. The discovery of plate tectonics later led to a revised cycle, primarily by [|John Tuzo Wilson]. In 1796 [|Georges Cuvier]published a paper on fossil elephants presented to the National Institute of Sciences and Arts in Paris. A proponent of [|catastrophism] Cuvier also published on biology and classification of animals. Still discussed as a viable alternative to uniformitarianism, especially among faith groups, the theory of catastrophism still has relevance in the curriculum. He published a monograph, with Brongniart, in 1811, on the stratigraphy of the Paris basin. In 1815 [|William ‘strata’ Smith] published a geological map, describing the geology of Britain, and in which Smith discussed fossil life forms as isochronous markers in sedimentary systems, and establishment of a temporal link between layers. In 1833 [|Charles Lyell]refined the principles of uniformitarianism, discussing Uniformity of Law, Uniformity of process, Uniformity of rate and Uniformity of state. This, along with the increasing popularity of archaeology among the middle classes, meant that the concept of geological time, and its application to humans, was established. The development of [|radiocarbon dating]in the 1940s and 1950s, and ongoing research in archaeology, geology and geography means that this is still an active area of scientific debate, with modern relevance, which can be brought into the classroom.

//Scientific terms// In the [|philosophy of science], certain terms are used in a specific way, which often differs from their colloquial use. Scientific [|laws] are analytical statements, considered to be universal; they are usually based on [|empirical observation], and can be disproved in the light of new evidence, for example, [|Boyle's Law]. By contrast, a [|theory] explains a circumstance, or set of circumstances, and may include several laws, for example [|String Theory] and the [|Theory of Evolution]. A postulate or [|axiom] is something which is considered to be self-evident, and may be a starting point for reasoning, while a [|hypothesis] is a suggested explanation which may be tested. A [|principle] can be a law, doctrine or assumption; however, in science the principle of a cause is the effect which produced it. Examples are [|Archimedes' Principle] and the [|Uncertainty Principle]. A rule has a generally predictable outcome, but is not considered to be universal as a law is universal. Rules include [|Bergman's rule] and [|Allen's rule] in biology. A [|concept] is generally held to be an abstract idea or mental symbol, although definitions are disputed.

// Historical perspective // Sedimentation is governed by laws which were discovered through observation. These laws were quantified by Steno (1) and developed by Hutton (2), Lyell (3) and Smith (4) among others. Geologists and geographers continue to study sedimentation, and to understand how it can be affected by different conditions (5,6). Traditionally, sedimentation is demonstrated in a beaker or jam jar, or in a large tank, in which sediments with different grain sizes are poured into water, agitated, and the sediment observed as it settles. This mirrors Steno's investigations. This demonstrates that different grains settle horizontally at different rates, leaving a banded appearance which can be observed and recorded. Similarly, transport and deposition are often demonstrated using sediments in flowing water to show the difference in transport potential of different sediments. The laws of sedimentation are often considered to be obvious to learners; these laws are: As identified by Steno (1): Law of superposition Principle of original horizontality Principle of lateral continuity

As identified by Lyell (Uniformitarianism) (3): Uniformity of Law Uniformity of process Uniformity of rate Uniformity of state Steno's laws mean that sediment will be laid down horizontally unless something stops it, and that each subsequent layer is younger that the one beneath it. This sequence will remain unless something happens afterwards to change it. Uniformitarianism means that in the past sedimentation took place in the same way as takes place now; that we can look at processes happening today and identify them happening in the same way in the past. The key point is that these laws had to be //discovered//, in the same way that other scientific laws had to be discovered, that by observing the behaviour of sediment the scientists were able to understand how sedimentation worked. These laws only seem obvious now because they have been known for a long time, and are fundamental to the study of sedimentation today. The activities below are designed to allow learners to experience some of the discovery for themselves.

//Obstacles to teaching and learning// Much of the data pertaining to misconceptions centres on college students, rather than those of school age. Anderson and Libarkin (7) found that misconceptions in Earth Sciences are very persistent, and that people continue to hold these misconceptions following instruction. Many were confused about deep time, and about the chronology of life on earth, and 65% did not believe that life forms could form oceanic rocks. Kortz (8) found that the use of worksheets and interactive groupings in tutorials (rather than a lecture format) helped to counter these misconceptions. It may be that, as only relatively little Earth Sciences content is taught at secondary school level (see schemes of work) that misconceptions persist because students learn the principles as older learners, and that misconceptions arise from learners being taught in a lecturing style (which persists in Universities), rather than in a more active way. Studies (9, 10, 11) have shown that few children appreciate the relationship between sedimentary rocks and the sedimentary processes by which they are formed. This links with the findings of Anderson and Libarkin (7) described above, in which college students do not appreciate that life forms can form oceanic rock. The major issues here appear to be with abstraction and extrapolation; the rock cycle cannot be shown to learners, and geological processes are difficult to demonstrate by their very nature. This means that learners have to make links between models and the real world, which depending on age and ability, may present more difficulty than other topics. Teaching must therefore use multiple models, relating this to empirical observation. Visits to interesting landscape forms are particularly useful to illustrate the topic. Confusion also arises when children associate the layers apparent in sedimentary rocks with the cleavage planes often apparent in metamorphic rocks (9, 11).Given the level of misconception in adult learners, and given that most UK science teachers have degrees in Chemistry, Biology and Physics, rather than Earth Sciences, it is possible that teacher misconceptions are compounding this difficulty. The current scheme of work in UK secondary schools addresses the principle of uniformitarianism, and of Smith's work, comparing the uniformitarian view with the conflicting hypothesis of catastrophism. However, this is discussed in conjunction with creationism, and creationist viewpoints, as well as 'young earth' viewpoints. This means that, rather than allowing for an exploration of paradigm shifts in science, the focus shifts to discussions of faith and religion, rather than how research builds on previous discoveries, the importance of observation and the proving or disproving of conflicting scientific theories. Teaching could focus on the quest for a scientifically valid chronology, starting with Usher, who tried to discover the age of the earth using the tools available to him at the time, moving through catastrophism and how and why uniformitarianism replaced it in the scientific world.

//References// 1. Steno, N. 1669. //Dissertationis prodromus//. Republished as Steno, N. 1916. //Dissertationis prodromus.// London: Macmillan and Company Ltd 2. Hutton, J. 1794. //An Investigation of the Principles of Knowledge and of the Progress of Reason, from Sense to Science and Philosophy//. Edinburgh: Strahan and Cadell 3. Lyell, C. 1830. //Principles of Geology// (three volumes). London: Murray 4. Smith, W. 1815. //A Delineation of the Strata of// // England //// and //// Wales ////, with part of //// Scotland ////. // John Carey: London. 5. Milliman, J. D. Meade, R. H. 1983. World-Wide Delivery of River Sediment to the Oceans Journal of Geology **91**: 1-21 6. Lowe, D. R. 1982. Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents //Journal of Sedimentary Research// **52**: 279-297 7. Anderson, S.W., and Libarkin, J., 2003. The retention of geologic misconceptions: alternative ideas that persist after instruction, //EOS//: **84** Abstract ED22E-07 8. Kortz, K. 2007. Paper No. 213-3. // Reducing student misconceptions in introductory geoscience courses using lecture tutorials. // 2007 GSA Denver Annual Meeting (28–31 October 2007) http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_127088.htm 9. Driver, R., Squires, A & Wood-Robinson, V. 1994. //Making sense of secondary science: research into children's ideas.// London & New York: RoutledgeFarmer 10. Happs, J. C. 1982. Rocks and minerals. //LISP Working Paper// **204**, Science Education Unit, University of Waikito. 11. 1985. Cognitive learning theory and classroom complexity. //Research in science and Technological Education.// **3**: 159-174