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New Directions in Wilson Cycle Concepts: Supercontinent and Tectonic Rock Cycles

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New Directions in Wilson Cycle Concepts: Supercontinent and Tectonic Rock Cycles New directions in Wilson Cycle concepts: Supercontinent and Tectonic Rock Cycles Steven J. Whitmeyer* Lynn S. Fichter Eric J. Pyle Department of Geology and Environmental Science, James Madison University, Harrisonburg, Virginia 22807, USA ABSTRACT environments by providing rapid interchange tem (lithosphere, atmosphere, hydrosphere, and between these two domains. Where factual biosphere) is dependent on interactions with the Modern earth science pedagogy is increas- information is of interest, e.g., when introduc- other components, through positive and nega- ingly based on an integrated systems frame- ing a topic or relaying important background tive feedback loops (Assaraf and Orion, 2005). work, where all of the major earth systems, information, the typical verbal primacy is In contrast, a review of pre-college and under- including lithospheric cycles, are interlinked observed. But in instances where spatial and graduate earth science curricula in the United and dependent on each other through feedback temporal relationships are of interest, such States suggests that earth science instruction is loops. Most secondary school and introductory as in the Rodinia and Pangaea superconti- still commonly organized into discrete bits of college-level geology courses present the con- nent cycles, and the “No Rock is Accidental” content. Generally speaking, learning objectives cepts of plate tectonics and rock classifi cations. tectonic rock cycle, the visualizations assume are arranged with elements such as landform However, many instructional approaches the primary role, with text-based annotations development, plate tectonics, and rock genesis fail to integrate these topics within an earth or verbal discussion as secondary. as separate, distinct topics, often with limited systems viewpoint, where supercontinent We conclude with discussions on the integrative connection (Hoffman and Barstow, cycles are viewed in both spatial and tempo- importance of inquiry-based educational 2007). The organization of these topics in a ral dimensions, and the classifi cation of rock approaches and effective ways of evaluating cause-effect fashion, or as a substantive part of types is intrinsically dependent on the tec- educational visualizations. We suggest that to an integrated system, is the exception, rather tonic, as well as the depositional environment best utilize the available media (digital and than the rule. in which they were formed. This contribution paper based), the level of cognitive engage- Not surprisingly, instructional materials refl ect presents new tectonic animations and images ment of the learning task should be closely tied this same descriptive and reductive organization. that allow students to investigate superconti- to a taxonomy of visualizations that encom- While many introductory college geology text- nent cycles (e.g., the assembly and breakup pass detailed, integrated representations and books present plate tectonic theory early in the of Rodinia, and the Paleozoic interactions animations. Inquiry-based interfaces, such as text as an organizing and potentially unifying of Laurentia, Gondwana, and Baltica) and we present in this paper, promote more mind- theme, most pre-college earth science texts pro- integrated Wilson Cycle and Tectonic Rock ful articulations of the desired learning tasks vide information on plate tectonics in a manner Cycles that equate rock genesis with tectonic and an increased retention of the subject that precludes connections with rock generation and environmental settings. Central to these material outside the bounds of the classroom. or landform development (Chambliss and Cal- visualizations is the concept that processes of Teaching a systems-based understanding of fee, 1989). As a result, the generation of rocks rock genesis have evolved, and will continue the Earth and the concepts of evolving tec- and landforms are disconnected from the tec- to evolve, through geologic time. We discuss tonic and rock cycles provides students with tonic and environmental processes that generate the conceptual and historical background for holistic foundations from which they can bet- them. Discussions of plate tectonics are limited each of these visualizations, and follow this ter evaluate, and make decisions about, their to paleontological and geophysical evidence for with detailed descriptions of, and educational living environment. the theory, such as Glossoptera fossils, volcano uses for, the images and animations. and earthquake occurrences, and paleomagnetic To be of optimal instructional utility, the Keywords: plate tectonics, Rodinia, Laurentia, data. More importantly, students are commonly animations and images consider the visual Wilson Cycle, rock cycle presented with a truncated depiction of global domain as a primary, rather than secondary tectonic history that only encompasses the instructional tool. As such, they are designed INTRODUCTION breakup of Pangaea (ca. 200 Ma) to the present, to function optimally in an inquiry-driven with prior supercontinent cycles represented, educational setting. They take into account Modern approaches to earth science educa- if at all, only in a discussion of geologic time the complex cognitive interactions between tion are increasingly focused on “systems think- (e.g., Tarbuck and Lutgens, 2005). The breakup visual and verbal representations in learning ing,” wherein each component of the earth sys- of Pangaea is presented as an isolated system, *[email protected] Geosphere; December 2007; v. 3; no. 6; p. 511–526; doi: 10.1130/GES00091.1; 8 fi gures; 3 animations. For permission to copy, contact [email protected] 511 © 2007 Geological Society of America Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/3/6/511/854441/i1553-040X-3-6-511.pdf by guest on 30 September 2021 Whitmeyer et al. and the dynamic nature of the Earth’s evolution- variables operating. “Prediction” in this sense introduced into the introductory classroom. In ary history is merely implied. In rock genesis, is not the same in the earth sciences as it is addition, as scientifi c ideas evolve, they tend where the three rock “types” (igneous, sedimen- in classical science. In complex systems like to become more complicated, and more diffi - tary, and metamorphic) are unifi ed through the the Earth, theories are less likely to predict a cult to teach. However, ideas and theories do ubiquitous “rock cycle” diagram, relationships specifi c outcome but rather an explanation progress in accuracy and complexity, and at are presented as a closed loop, with little regard of the underlying mechanisms at work; e.g., some point teaching what is simple and famil- for how the types and volumes of rocks on Earth under a particular set of conditions, a certain iar does both the discipline and the student a have evolved through billions of years of the set of structures and rocks will form. Time is disservice. Decision making in these cases is Earth’s tectonic history. an essential component, because the slow rates not clean and simple; academia benefi ts from Part of the handicap with presenting topics of tectonic and evolutionary processes require the dynamic tension between conservative like the Earth’s dynamic history and rock genesis millions or billions of years to accomplish the foundations and new directions precipitated as integrated systems is that textbooks and even signifi cant changes apparent in the rock record. by modern research. In the following sections PowerPoint illustrations are primarily descrip- This viewpoint is fundamental in the earth sci- of this paper, we argue that theories about the tive rather than generative, wherein complex ences, where time is used in a forward and Earth’s tectonic processes have evolved to the dynamic processes are reduced to static images. backward manner—predictions as well as “ret- point where we need to reevaluate what we Comprehension is also made diffi cult by the rodictions” (Frodeman, 1995). teach and how we teach it. We begin with a range of scales of observation at which Earth Earth scientists are still a long way from fully brief summary of how rapidly changing scien- processes function—from the microscopic to explaining or integrating how the complex world tifi c ideas have infl uenced the teaching of earth the global and from microseconds to hundreds works, i.e., how all the Earth’s systems interact tectonics over the past half century and then of millions of years. Integration of these pro- to produce the outcomes we observe. However, discuss why existing depictions of tectonic cesses into an effective instructional approach we now appreciate the necessity of viewing the cycles and rock cycles in educational materi- is an ongoing challenge, and it is within this Earth and teaching Earth’s history in the context als need further refi nement within a broader time-dependent, process-oriented framework of interconnected and interdependent complex earth systems context. that modern computer-aided visualizations can systems. This contribution presents spatial and be effectively utilized. temporal animations of plate tectonic processes Geosynclinal Theory to Modern Tectonic The educational potential for visualizations and sequential diagrams of modern Wilson Models has been recognized by the American Associa- Cycles and Tectonic Rock Cycles that integrate tion for the Advancement of Science (AAAS), tectonic processes and rock genesis in an evolu- Before the majority of American geosci- through the textbook analysis framework devel-
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