Steven J. Whitmeyer

The digital revolution in geologic mapping

Geologic field data collection, analysis, and map compilation are undergoing a revolution in methods, largely precipitated by global positioning system (GPS) and geographic information system (GIS) equipped mobile computers paired with virtual globe visualizations. Modern, ruggedized personal digital assistants (PDAs) and tablet PCs can record a wide spectrum of geologic data and facilitate iterative geologic map construction and evaluation on location in the field. Spatial data, maps, and interpretations can be presented in a variety of formats on virtual globes, such as Google Earth and NASA World Wind, given only a basic knowledge of scripting languages. As a case study, we present geologic maps assembled in Google Earth that are based on digital field data. Interactive features of these maps include (1) the ability to zoom, pan, and tilt the terrain and map to any desired viewpoint; (2) selectable, draped polygons representing the spatial extent of geologic units that can be rendered semi-transparent, allowing the viewer to examine the underlying terrain; (3) vertical cross sections that emerge from the subsurface in their proper location and orientation; (4) structural symbols (e.g., strike and dip), positioned at outcrop locations, that can display associated metadata; and (5) other data, such as digital photos or sketches, as clickable objects in their correct field locations. Google Earth–based interactive geologic maps communicate data and interpretations in a format that is more intuitive and easy to grasp than the traditional format of paper maps and cross sections. The virtual three-dimensional (3-D) interface removes much of the cognitive barrier of attempting to visualize 3-D features from a two-dimensional map or cross section. Thus, the digital revolution in geologic mapping is finally providing geosci entists with tools to present important concepts in an intuitive format understandable to the expert and layperson alike.

Synthesis of Results from the Cd‐Rom Experiment: 4‐D Image of the Lithosphere Beneath the Rocky Mountains and Implications for Understanding the Evolution of Continental Lithosphere

The CD-ROM experiment has produced a new 4-D understanding of the structure and evolution of the lithosphere of the southern Rocky Mountain region. We identify relicts of at least four subduction zones that were formed during assembly of dominantly oceanic terranes in the Paleoproterozoic. Crustal provinces with different geologic histories correspond to distinct mantle velocity domains, with profound mantle velocity contrasts associated with the ancient sutures. Typically, the transitions between the velocity domains are tabular, dipping, extend from the base of the crust to depths of 150-200 km, and some contain dipping mantle anisotropy. The present day heterogeneous mantle structure, although strongly influenced by ancient compositional variations, has undergone different degrees of partial melting due to Cenozoic heating and/or hydration caused by transient plumes or asthenospheric convection within the wide western U.S. active plate margin. A high-velocity mafic lower crust is present throughout the Rocky Mountains, and there is ∼10-km-scale Moho topography. Both are interpreted to record progressive and ongoing differentiation of lithosphere, and a Moho that has changed position due to flux of basalt from the mantle to the crust. The mafic lower crust evolved diachronously via concentration of mafic restite during arc formation (pre-1.70 Ga), collision-related differentiation and granite genesis (1.70-1.62 Ga), and several episodes of basaltic underplating (1.45-1.35 Ga, ∼1.1 Ga, and Cenozoic). Epeirogenic uplift of the western U.S. and Rocky Mountain regions, driven by mantle magmatism, continues to cause reactivation of the heterogeneous lithosphere in the Cenozoic, resulting in differential uplift of the Rocky Mountains.

Sequential ductile to brittle reactivation of major fault zones along the accretionary margin of Gondwana in Central Argentina

Abstract Metamorphic and plutonic basement rocks and cover sequences of the Eastern Sierras Pampeans, Argentina, have undergone multiple episodes of fault reactivation. Faults take advantage of mid- to late Cambrian, NW-SE-striking, steeply east-dipping foliations in Vendian-aged accretionary prism metasedimentary rocks. Foliations in peraluminous schists, paragneisses and migmatites are deflected into late Cambrian amphibolite-grade high-strain zones. Greenschist-grade mylonite zones and thick retrogressed ultramylonite zones with mainly NNW strikes, easterly dips, and east-over-west movement, affect the metasedimentary rocks and Ordovician-aged intrusive rocks and are presumably related to early Devonian accretion of terranes to the west of Gondwana. pseudotachylyte veins occur in nearly all mylonite zones. Brittle deformation during Carboniferous to Triassic time produced major pull-apart basins located above terrane boundaries. Outcrop patterns of Triassic to Cretaceous sedimentary rocks are consistent with transtensional pull-apart basins followed by Andean transpressional deformation. The theoretical basis for fault reactivation and production of ‘short cuts’ is examined in the context of Tertiary to Recent basin inversion faults. The inversion faults follow the Palaeozoic trends and produce the present-day NNW-oriented, deep sedimentary basins and intervening ranges of basement rocks.

Geoscience Field Education: A Recent Resurgence

Field education traditionally has been an integral component of undergraduate geoscience curricula. Students have learned the fundamentals of field techniques during core geology courses and have honed their field credentials during class-specific field trips, semester-long field courses, and capstone summer field camps. In many geoscience departments, field camp remains a graduation requirement, and more than 100 field camps currently are offered by U.S. universities and colleges (see http://geology.com/field-camp.shtml). During the past several decades, however, many geoscience departments have moved away from traditional geologic fieldwork and toward a broader theoretical and laboratory-intensive focus that encompasses a range of subdisciplines. Trends that have influenced these shifts include (1) the decline in the late twentieth century of the petroleum and mining industries, which have consistently championed the values of fieldwork; (2) a decrease in the number of professional jobs that incorporate field mapping; (3) a decline in the number of geoscience majors nationwide [American Geological Institute (AGI), 2009]; and (4) barriers to fieldwork, including time requirements, cost, liability, and decreasing access to field sites.

Expanding Evolutionary Theory Beyond Darwinism with Elaborating, Self-Organizing, and Fractionating Complex Evolutionary Systems

Earth systems increase in complexity, diversity, and interconnectedness with time, driven by tectonic/solar energy that keeps the systems far from equilibrium. The evolution of Earth systems is facilitated by three evolutionary mechanisms: elaboration, fractionation, and self-organization, that share universality features not found in more familiar equilibrium systems. These features include: 1. evolution to sensitive dependent critical states, 2. avalanches of changes following power law distributions with fractal organization, and 3. dynamic behaviour as strange attractors that often exhibit bistable behaviour. We propose a new approach to teaching Earth systems theory, where theoretical underpinnings of evolutionary mechanisms are introduced, followed by explorations of how the mechanisms interact to integrate the lithosphere, atmosphere, hydrosphere, and biosphere into a unitary evolutionary system. We incorporate conceptual and computer-based interactive models (included here as educational resources) within our lesson plans that illustrate a hierarchy of principles and experimental outcomes for evolutionary mechanisms. Application of this educational framework requires explicating complex systems mechanisms and their interactions, exploring their applicability to Earth systems, and imbedding them in high school as well as college introductory and upper level Earth Science classrooms to put all Earth systems on a comprehensive, integrated, universal evolutionary theoretical foundation.

New directions in Wilson Cycle concepts: Supercontinent and Tectonic Rock Cycles

Modern earth science pedagogy is increasingly based on an integrated systems framework, where all of the major earth systems, including lithospheric cycles, are interlinked and dependent on each other through feedback loops. Most secondary school and introductory college-level geology courses present the concepts of plate tectonics and rock classifi cations. However, many instructional approaches fail to integrate these topics within an earth systems viewpoint, where supercontinent cycles are viewed in both spatial and temporal dimensions, and the classifi cation of rock types is intrinsically dependent on the tectonic, as well as the depositional environment in which they were formed. This contribution presents new tectonic animations and images that allow students to investigate supercontinent cycles (e.g., the assembly and breakup of Rodinia, and the Paleozoic interactions of Laurentia, Gondwana, and Baltica) and integrated Wilson Cycle and Tectonic Rock Cycles that equate rock genesis with tectonic and environmental settings. Central to these visualizations is the concept that processes of rock genesis have evolved, and will continue to evolve, through geologic time. We discuss the conceptual and historical background for each of these visualizations, and follow this with detailed descriptions of, and educational uses for, the images and animations. To be of optimal instructional utility, the animations and images consider the visual domain as a primary, rather than secondary instructional tool. As such, they are designed to function optimally in an inquiry-driven educational setting. They take into account the complex cognitive interactions between visual and verbal representations in learning environments by providing rapid interchange between these two domains. Where factual information is of interest, e.g., when introducing a topic or relaying important background information, the typical verbal primacy is observed. But in instances where spatial and temporal relationships are of interest, such as in the Rodinia and Pangaea supercontinent cycles, and the “No Rock is Accidental” tectonic rock cycle, the visualizations assume the primary role, with text-based annotations or verbal discussion as secondary. We conclude with discussions on the importance of inquiry-based educational approaches and effective ways of evaluating educational visualizations. We suggest that to best utilize the available media (digital and paper based), the level of cognitive engagement of the learning task should be closely tied to a taxonomy of visualizations that encompass detailed, integrated representations and animations. Inquiry-based interfaces, such as we present in this paper, promote more mindful articulations of the desired learning tasks and an increased retention of the subject material outside the bounds of the classroom. Teaching a systems-based understanding of the Earth and the concepts of evolving tectonic and rock cycles provides students with holistic foundations from which they can better evaluate, and make decisions about, their living environment.

Does the arc-accretion model adequately explain the Paleoproterozoic evolution of southern Laurentia: An expanded interpretation: COMMENT AND REPLY COMMENT

Assembly of lithosphere in southern Laurentia is best interpreted to have taken place along a long-lived (1.8–1.0 Ga) active margin via subduction-accretion processes broadly analogous to present-day convergence between Australia and Indonesia ([Karlstrom and Bowring, 1988][1]; [Karlstrom et al.,

MaRGEE: Move and Rotate Google Earth Elements

Abstract Google Earth is recognized as a highly effective visualization tool for geospatial information. However, there remain serious limitations that have hindered its acceptance as a tool for research and education in the geosciences. One significant limitation is the inability to translate or rotate geometrical elements on the Google Earth virtual globe. Here we present a new JavaScript web application to “Move and Rotate Google Earth Elements” (MaRGEE). MaRGEE includes tools to simplify, translate, and rotate elements, add intermediate steps to a transposition, and batch process multiple transpositions. The transposition algorithm uses spherical geometry calculations, such as the haversine formula, to accurately reposition groups of points, paths, and polygons on the Google Earth globe without distortion. Due to the imminent deprecation of the Google Earth API and browser plugin, MaRGEE uses a Google Maps interface to facilitate and illustrate the transpositions. However, the inherent spatial distortions that result from the Google Maps Web Mercator projection are not apparent once the transposed elements are saved as a KML file and opened in Google Earth. Potential applications of the MaRGEE toolkit include tectonic reconstructions, the movements of glaciers or thrust sheets, and time-based animations of other large- and small-scale geologic processes.

Strategies and Rubrics for Teaching Chaos and Complex Systems Theories as Elaborating, Self-Organizing, and Fractionating Evolutionary Systems

To say Earth systems are complex, is not the same as saying they are a complex system. A complex system, in the technical sense, is a group of “agents” (individual interacting units, like birds in a flock, sand grains in a ripple, or individual units of friction along a fault zone), existing far from equilibrium, interacting through positive and negative feedbacks, forming interdependent, dynamic, evolutionary networks, that possess universality properties common to all complex systems (bifurcations, sensitive dependence, fractal organization, and avalanche behaviour that follows power-law distributions.) Chaos/complex systems theory behaviors are explicit, with their own assumptions, approaches, cognitive tools, and models that must be taught as deliberately and systematically as the equilibrium principles normally taught to students. We present a learning progression of concept building from chaos theory, through a variety of complex systems, and ending with how such systems result in increases in complexity, diversity, order, and/or interconnectedness with time-that is, evolve. Quantitative and qualitative course-end assessment data indicate that students who have gone through the rubrics are receptive to the ideas, and willing to continue to learn about, apply, and be influenced by them. The reliability/validity is strongly supported by open, written student comments.

Exploring the reasons for the seasons using Google Earth, 3D models, and plots

ABSTRACT Public understanding of climate and climate change is of broad societal importance. However, misconceptions regarding reasons for the seasons abound amongst students, teachers, and the public, many of whom believe that seasonality is caused by large variations in Earth’s distance from the Sun. Misconceptions may be reinforced by textbook illustrations that exaggerate eccentricity or show an inclined view of Earth’s near-circular orbit. Textbook explanations that omit multiple factors influencing seasons, that do not mesh with students’ experiences, or that are erroneous, hinder scientifically valid reasoning. Studies show that many teachers share their students’ misconceptions, and even when they understand basic concepts, teachers may fail to appreciate the range of factors contributing to seasonal change, or their relative importance. We have therefore developed a learning resource using Google Earth, a virtual globe with other useful, weather- and climate-related visualizations. A classroom test of 27 undergraduates in a public research university showed that 15 improved their test scores after the Google Earth-based laboratory class, whereas 5 disimproved. Mean correct answers rose from 4.7/10 to 6/10, giving a paired t-test value of 0.21. After using Google Earth, students are helped to segue to a heliocentric view.