The new frontier of interactive, digital geologic maps: Google Earth ...

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The Geological Society of America Special Paper 492 2012

The new frontier of interactive, digital geologic maps: Google Earth–based multi-level maps of Virginia geology Owen P. Shufeldt Steven J. Whitmeyer* Department of Geology & Environmental Science, James Madison University, Memorial Hall MSC 6903, Harrisonburg, Virginia 22807, USA Christopher M. Bailey Geology Department, College of William & Mary, McGlothlin-Street Hall 215, Williamsburg, Virginia 23187, USA ABSTRACT Digital geologic maps that use a virtual globe interface, like Google Earth (GE), are a relatively new medium for presenting geologic data and interpretations. This format incorporates significant advantages over traditional paper geologic maps and cross sections, including: • A user-friendly and intuitive interface for novice users, which enhances the utility of geologic information for students and the general public; • The ability to view multiple maps simultaneously and seamlessly transition between maps by zooming or panning; • The option of displaying cross sections in situ on geologic maps as vertical interpretations of above ground or subsurface geology; and • A facility for integrating map interpretations with individual outcrop and field data, which traditionally has been relegated to field books. This paper outlines a digital maps package, composed of geologic maps of regions of Virginia, as a proof of concept and template for possible future expansion beyond state boundaries or into the realm of soils, geomorphological or hydrological maps. Through collaboration between universities, state agencies, and federal organizations we have assembled a multi-layered, fully interactive map accessible through two portals: the stand-alone Google Earth application, and as a web page using the GE web browser plug-in (GE API). All maps within this package have selectable polygons, polylines (“paths”), and points (“placemarks”), many of which contain associated metadata, such as lithologic descriptions, fault information, outcrop orientation data, etc. At the smallest scale, a generalized geologic map of Virginia is displayed with a selectable overlay of regional physiographic provinces. As users pan and zoom, the maps automatically transition from generalized statewide maps to more refined

*Corresponding author: [email protected]. Shufeldt, O.P., Whitmeyer, S.J., and Bailey, C.M., 2012, The new frontier of interactive, digital geologic maps: Google Earth–based multi-level maps of Virginia geology, in Whitmeyer, S.J., Bailey, J.E., De Paor, D.G., and Ornduff, T., eds., Google Earth and Virtual Visualizations in Geoscience Education and Research: Geological Society of America Special Paper 492, p. 147-163, doi:10.1130/2012.2492(11). For permission to copy, contact [email protected]. © 2012 The Geological Society of America. All rights reserved.

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Shufeldt et al. regional maps and 1:24,000 scale quadrangle maps. Many of the map components (cross-sections, explanations, and orientation symbols) cannot be created directly in GE but are added to the digital maps using KML scripts derived from an HTMLbased toolkit. Challenges related to the method of digital map development described herein include: effective importation of vector data from other GIS databases, style limitations inherent in GE, and time-consuming labor associated with the digitization of polygons and polylines in GE. There are also conceptual challenges at the user interface level, including possible misconceptions with the display of vertical cross sections due to the inability to look below the GE digital elevation model and associated surface imagery.

INTRODUCTION Geoscience educators and professionals are often challenged by using 2-D static tools to present and teach 3-D spatial concepts like rock orientations and folded structures. Studies have discussed this difficulty while describing challenges faced when performing Euclidean or projective spatial tasks (Kastens and Ishikawa, 2006). The advent of virtual globes has provided a new medium for addressing these challenges (Butler, 2006; Lisle, 2006; Goodchild, 2008) through their facility in displaying spatial geological data in a virtual 3-D, dynamic environment (Hennessy and Feely, 2008; De Paor and Whitmeyer, 2011). Techniques of displaying geological data on virtual globes include overlaying map images, creating individual selectable polygons, importing data from a Geographic Information System (GIS) (Whitmeyer et al., 2010), and modifying keyhole markup language scripts (KML) to link maps with associated Collaborative Design Activity (COLLADA) models of structural orientation symbols and cross sections (De Paor and Whitmeyer, 2011). While many of these topics have been previously presented and discussed (e.g., articles in Chen and Bailey, 2011), the literature lacks a thorough manual for creating a complete, multi-level, interactive maps package for virtual globes, specifically Google Earth. This paper discusses the collaborative development of a prototype maps package for Google Earth (GE) displaying Virginia geology and containing a full range of geological data, including maps at multiple scales that automatically transition as users zoom in and out. The maps contain the most important features of geologic maps: lithologic units and faults with descriptions (metadata), structural data (orientation symbols of planar features), cross sections, and outcrop photos and notes. Other components include a layer that highlights the 7.5 min quadrangles that currently are included in the maps package with hyperlinks to state geological survey (Virginia Department of Mines, Minerals and Energy) publications and reference material for each quadrangle. This paper will also briefly discuss the GE web browser plug-in (GE API) and the advantages and disadvantages of displaying this maps package in such a platform. Finally, potential uses of digital geologic maps packages for professionals, educators, and the general public will be addressed.

OVERVIEW OF THE VIRGINIA GEOLOGIC MAPS PACKAGE The Virginia geologic maps package is a GE-based, integrated set of maps, cross sections, and outcrop-scale data designed as an intuitive interface for a broad spectrum of users, including geology professionals, educators, students, and the general public. To access the maps package, either download the master KML file at: http://csmres.jmu.edu/Geollab/Whitmeyer/web/ visuals/GoogleEarth/VirginiaGeologicMaps.kml or view it as a web page by utilizing the GE API plugin at: http://csmres.jmu.edu/Geollab/Whitmeyer/web/ visuals/GoogleEarth/Virginia/VirginiaMaps.html Fast, seamless transitions between statewide maps, regional 1:50,000 scale geologic maps, and detailed 7.5 min quadrangle (1:24,000 scale) geologic maps are key features of the maps package. The user controls what maps and features are displayed by zooming and panning in the GE window. Similarly, detailed outcrop data, such as orientation symbols and photos, are only visible when the user is zoomed in close to the ground surface. This design prevents voluminous point data from cluttering the user’s field of view when zoomed out to smaller scales. At the smallest scale, where the field of view encompasses Virginia (or more of the eastern seaboard) a map of the physiographic provinces of Virginia (Fig. 1A) is visible, with the option to show the extensions of these physiographic provinces to the north (Fig. 1B) and south (Fig. 1C) by toggling check boxes in the GE Layers menu. These maps, and others in this maps package, were digitized from a variety of sources, the citations for which can be found in the description pop-up bubbles associated with each colored polygon. As the user zooms closer to the ground surface, the physiographic province maps automatically transition to a generalized geologic map of Virginia (Fig. 2A; C.M. Bailey’s 1999 “Simplified Geologic Map of Virginia,” http://web.wm.edu/geology/ virginia/provinces/pdf/va_geology.pdf). A west-to-east cross

The new frontier of interactive, digital geologic maps

Figure 1. (A) Physiographic province map of Virginia with the provinces labeled. (B) Physiographic province map of the northeastern United States showing a general description of the selected polygon in the pop-up balloon. (C) Physiographic province map of the southeastern United States showing a general description of the selected polygon in the pop-up balloon.

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Figure 2. (A) Simplified geologic map of Virginia as polygons with information in pop-up balloons (after C.M. Bailey’s 1999 “Simplified Geologic Map of Virginia,” http://web .wm.edu/geology/virginia/provinces/pdf/va_geology.pdf). (Continued).

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Figure 2. (B) Northwest-southeast cross section interpreting subsurface geology spanning Virginia (after Williams et al., 2005). The cross section is elevated out of the subsurface by clicking on the “Elevate I-64 Cross Section” Tour highlighted in blue.

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section interpretation of the subsurface geology can be viewed by tilting the view and running the “Elevate I-64 Cross Section” tour in the Virginia I-64 Cross Section folder (Fig. 2B). Continued zooming in the central Blue Ridge region displays a 1:50,000 scale map of the Blue Ridge to Valley and Ridge transition in the southern Shenandoah National Park area (Fig. 3A; Bailey, C.M., Gattuso, A.P., and Tadlock, E.D., 2008, Digital Geologic Map of the southern Shenandoah National Park region, Virginia, 1:50,000 scale, unpublished). With continued zooming in the

Shenandoah Valley region, the largest scale (1:24,000) geologic maps appear (Fig. 3B). At present, the coverage of intermediateto large-scale maps is restricted to northwestern Virginia. Figure 3B shows a typical region of partial coverage in the vicinity of Harrisonburg, Virginia. Work to expand map coverage at the 1:50,000 and 1:24,000 scales is ongoing. Below we briefly discuss the geologic setting for Virginia and the Shenandoah Valley / Blue Ridge region, after which we discuss design components of the maps package in detail.

Figure 3. (A) 1:50,000 scale geologic map of the southern region of Shenandoah National Park and surrounding areas (after Bailey, C.M., Gattuso, A.P., and Tadlock, E.D., 2008, Digital Geologic Map of the southern Shenandoah National Park region, Virginia, 1:50,000 scale, unpublished). (B) Collection of 1:24,000 scale 7.5 min quadrangle geologic maps covering much of the same area as (A) (after Forte et al., 2005; Campbell et al., 2006, and references therein), with gaps showing quadrangles that have not yet been included in this map compilation.

The new frontier of interactive, digital geologic maps GEOLOGIC OVERVIEW OF VIRGINIA The geology of Virginia is quite diverse, ranging from sediments currently being deposited in marshes and barrier islands along the Atlantic coast to Eocene volcanic rocks to metamorphic rocks formed over a billion years ago. At present, Virginia is located well within the North American tectonic plate along a passive margin setting. Virginia’s geology is the result of two supercontinent cycles during the last billion years: (1) the formation of Rodinia to the opening of the Iapetus ocean, and (2) the formation of Pangaea to the opening of the Atlantic ocean. Traditionally, Virginia is divided into five physiographic provinces, each with its own unique topographic character that reflects the underlying materials and geologic structure of the province (Fig. 1A; Fenneman and Johnson, 1946; Bingham, 1991). From west to east, the provinces include the Allegheny Plateau, Valley and Ridge, Blue Ridge, Piedmont, and Coastal Plain (Fig. 1A). The Allegheny Plateau and Valley and Ridge provinces are part of the Appalachian foreland basin and are underlain by Paleozoic sedimentary rocks. Rocks on the Plateau are generally flat-lying, while rocks in the Valley and Ridge were folded and faulted during the late Paleozoic Alleghanian Orogeny (Fig. 2; Virginia Division of Mineral Resources, 1993, 2003). Differential erosion in the Valley and Ridge has produced the distinctive topography of the province. The Blue Ridge province encompasses Virginia’s highest peaks and is characterized by relatively high relief. Rocks of the Blue Ridge province include 1.0–1.2 Ga granitoid gneisses and an overlying Neoproterozoic–Early Paleozoic cover sequence of metamorphosed volcanic and sedimentary rocks (Fig. 2; Bailey et al., 2006). A complex suite of Proterozoic to Paleozoic metamorphic and igneous rocks underlies the Piedmont province, forming the hinterland of the Appalachian Orogen, sensu lato (Horton et al., 1989). Major ductile fault zones and faults bound Piedmont terranes, and the province is cut by a series of early Mesozoic rift basins. Early Jurassic magmatism produced dikes, sills, and flows in the Culpeper basin, and mafic dikes throughout much of the Piedmont (Virginia Division of Mineral Resources, 1993, 2003). The Coastal Plain consists of a gently inclined sequence of Cretaceous to Recent sedimentary rocks and sediments deposited under shallow marine, estuarine, and fluvial conditions associated with changing sea levels during the past 100 million years (Fig. 2; Mixon et al., 1989; Virginia Division of Mineral Resources, 1993, 2003). MAP DEVELOPMENT IN GOOGLE EARTH The integrated geologic maps package described in detail below was developed specifically for presentation using Google Earth, allowing for features to be completely controlled and displayed using the tools and controls within the program. However, the geologic maps displayed were, almost without exception, originally developed using other graphics platforms, such as ArcGIS and Adobe Illustrator. Thus, GE map development typically begins in one of two ways: by manually creating polygons and

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paths (poly-lines) through tracing over an overlay imported as a raster image (JPEG, PNG, TIFF); or by importing shapefile data from ArcGIS and modifying the vector data (polygon colors, line weights, etc.) to be consistent with the rest of the maps package. Individual polygons and paths are used for lithologic units and linear features, respectively, to enable users to access descriptions and metadata via pop-up bubbles by clicking on the features. This can also be accomplished by creating image overlays for each unit as a separate PNG (portable networks graphics) files, but Google Earth renders raster overlays much more slowly than vector polygons. Fast and efficient rendering of map images is a constant challenge for any maps package that displays data on a quadrangle or larger scale. Image Import Method As discussed above, many digital maps are created in programs like Adobe Illustrator, where the final map can be exported as a JPEG or PNG file. If the map is a quadrangle, with known bounding coordinates, importing these files into GE simply requires using the “Add Image Overlay” tool and specifying the coordinates for the north, south, east, and west boundaries of the map. Once this is done, polygons can be created using the Add Polygon feature to manually trace the outline of each lithologic unit. To enhance interactivity, adding unit descriptions into the “Description” field of the polygon allows users to click anywhere within the polygon and obtain a pop-up balloon with the lithologic information. Shapefile Import Method For maps constructed in ArcGIS, the latest versions of Google Earth Pro allow the user to import unit polygons or linework from a shapefile (.shp). However, Google Earth Pro currently limits the number of unique colors that can be assigned to shapefile elements, and thus the shapefile sometimes is necessarily imported with a random color scheme, and all polygon colors have to be manually reassigned. Our currently preferred method is to export shapefiles or layers as KML files out of ArcGIS using Arc Toolbox, which does a better job of preserving polygon styles following the shapefile to KML conversion. Linework, however, is still problematic when imported into GE from ArcGIS, as individual lines in ArcGIS often become segmented into separate lines when converted to KML code. Thus, we typically have to manually redigitize all of the linework within GE. Another issue with lines in GE is that there is no option for creating ornamentations. Therefore, adding ornaments like barbs on thrust faults or tick marks on normal faults is a non-trivial task. Adding Structural Symbols At the largest map scale (1:24,000), structural data often is necessary to get a thorough understanding of the surface and subsurface geology. However, since this GE maps package is designed for a wide range of users, our goal is to display

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Figure 4. (A) Oblique view of Massanutten Mountain, Virginia, looking northwest with oriented, 3-D strike and dip symbols hovering above topography. (B) Orientation Symbol Generator web page. (Continued.)

The new frontier of interactive, digital geologic maps structural data in a manner that attempts to preclude typical confusion regarding strike and dip of planar surfaces (Kastens and Ishikawa, 2006). As discussed in Whitmeyer et al. (2010), we have found that the most accurate and intuitive way to display outcrop orientation symbols is as 3-D models hovering slightly above the ground surface (Fig. 4A). The construction of these models previously required some knowledge of SketchUp, COLLADA models, and KML scripting (De Paor and Whitmeyer, 2011). Some basic KML scripting is included in Tables 1 and 2 and within other papers in this volume (e.g., De Paor et al., this volume, Chapter 6), but many geologists will find it easier to use a web-based tool we have developed that partially automates the creation and positioning of orientation symbols. The Orientation Symbol Generator (Fig. 4B) is available at: http://csmres.jmu.edu/Geollab/Whitmeyer/web/visuals/ maptools.html. To use this tool, the user supplies location (latitude and longitude) coordinates, formation name, azimuth of strike (or

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trend), dip (or plunge) angle and direction, and any additional notes about the outcrop. This generates code in a pop-up window that is saved as a KML file (Table 1), which, once opened in Google Earth, displays a series of oriented 3-D strike and dip symbols (Fig. 4A) or lineation arrows. While all structural symbols created with this tool display basic outcrop data (lithologic unit, structural orientation) when selected, symbols can also include pictures of, and notes about, the outcrop at which the measurement was taken (Fig. 4C). The description and images can be added to the text balloon using basic KML code (see Table 1). Adding Cross Sections In order to display cross sections in GE, COLLADA models of transparent vertical rectangles are necessary, on which PNG images of the geologic interpretation are superimposed. Methods for doing this using SketchUp and the model import feature in GE have been described elsewhere (De Paor and Whitmeyer, 2011; Hill and Harrison, this volume). To simplify this process and remove the necessity of using SketchUp, a web-based tool

Figure 4. (C) View of 3-D strike and dip model with a text balloon containing metadata and an outcrop photo. See Table 1 for the relevant KML code.

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TABLE 1. KML CODE GENERATED BY STRIKE AND DIP SYMBOL GENERATOR WEB PAGE AT http://csmres.jmu.edu/geollab/whitmeyer/web/visuals/googleearth/tools/sd.html Symbol3 relativeToGround -78.74285500000001 38.406964 40 240 0 -89 40 50 50 http://csmres.jmu.edu/Geollab/Whitmeyer/web/visuals/ GoogleEarth/tools/SDsymbol.dae Massanutten Fm.3 Massanutten Fm.
strike & dip of bedding: 240, 89 N

Notes:
Subvertical sandstones offset at Harshberger Gap


View looking west from Massanutten Rd. at Harshberger Gap
(4" wide compass case for scale)]]> #sn_shaded_dot30 -78.74285500000001,38.406964,0 89 #sn_no_icon -78.74335500000001,38.407364,0 Note: Three Placemarks are generated for each orientation symbol. The first one listed displays the 3-D model of the symbol positioned with the and aligned using the tags. Note that the symbol model is stored on an external server and referenced by the tags. The second Placemark contains outcrop information that appears in a pop-up balloon. In this case it includes a photo stored on an external server and referenced with the tag. The third Placemark displays the dip number next to the symbol. This is an option that can be selected on the Strike and Dip Symbol Generator web page.

The new frontier of interactive, digital geologic maps has been created to position a cross section in the correct location and orientation in GE. This tool (Fig. 5A) is available at: http://csmres.jmu.edu/Geollab/Whitmeyer/web/visuals/ GoogleEarth/tools/XS.html. The cross section image must first be constructed in a graphics program like Adobe Illustrator. The image file must have a transparent background and be saved in the .png file format to the user’s desktop. A reference .dae (digital asset exchange) file containing the COLLADA model for the vertical cross section rectangle must also be downloaded from the website and saved to the user’s desktop. Once these files are in place, the user enters latitude and longitude data, desired altitude, orientation (azimuthal strike of cross section), length, and height (in meters) of the cross section image into the input fields on the web page. This generates (in a pop-up window) the KML code for positioning the cross section model that is saved with a .kml file extension and opened in GE (Fig. 5B). If desired, all of the elements of the cross section can be packaged together as a stand-alone file by saving the cross section folder as a KMZ file from within Google Earth. As is evident from the Figure 5B, there are some drawbacks to cross section display in GE. First, GE does not easily or accurately display images below the ground surface. One way to get around this problem is to add a feature to elevate or “drag” the cross sections up out of the ground to show that they are vertical subsurface interpretations of the geology shown on the map. This can be done by creating a GE Tour, which is an option on the web page shown in Figure 5A (detailed in De Paor et al., this volume, Chapter 6) or by using the time slider feature (upper left corner of Fig. 5B) as detailed in De Paor and Whitmeyer (2011). The time slider feature can also be used to display a series of cross sections above the terrain, which can illustrate along-strike features such as a down-plunge projection (i.e., the syncline shown in Figure 5B). Citing Authors and Copyrights Building an integrated digital maps package necessitates assembling existing geologic maps from many sources. This prompts the question of how to display source information for the authors and organizations that created the individual maps. We list references at the bottoms of pop-up text balloons for material cited from publications, but users will not see these references if the balloons aren’t opened. Users can be forced to view a pop-up window when individual maps are first loaded (e.g., the White Hall quadrangle; Fig. 6) by adding a to the Network Link folder (see third in Table 2). For basic source acknowledgment we decided to use screen overlays of logos for the authoring institutions and have the logos appear or disappear depending on whether the specific map is visible to the user (bottom left corner of Figures 3B, 4C, 5B). Screen overlays cannot be created from within the GE application; they require external KML coding. Screen Overlays can be created using the web page at

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http://csmres.jmu.edu/Geollab/Whitmeyer/web/visuals/ GoogleEarth/tools/SO.html or see the KML tutorial at http://code.google.com/apis/kml/documentation/kml _tut.html. Integrating the Maps The most significant concern for creating a multi-layer, integrated system of geologic maps is speed of rendering of the images. Any digital maps package becomes less convenient for the general public to use if it takes a significant amount of time for individual maps to load. Early versions of our maps package were developed with image overlays for lithologic units, which caused GE to quickly grind to a halt as the number of maps on display increased. Similarly, our early attempts to display the full aerial extent of every map at all times, regardless of the viewpoint of the user, slowed GE considerably. Thus, we settled on vector polygons and paths for lithologic units and linework, and we developed a Network Linked system of individual map files controlled through a downloadable master KML file. Network Links is the mechanism that allows KML files to load other KML files based on certain criteria. When used with , , and tags the master KML file can control when maps (as individual KML or KMZ files) are displayed based on the viewpoint of the user. Table 2 shows KML code from the VirginiaGeologicMaps.kml master control file, downloadable from: http://csmres.jmu.edu/Geollab/Whitmeyer/web/visuals/ GoogleEarth/VirginiaGeologicMaps.kml The tag defines the view area of the Google Earth window within which a given map will be displayed. The children of the tag include which sets the boundaries of the viewable area, and (Level of detail) which sets the zoom altitude at which the map will be displayed. The use of these tags greatly enhances the speed of the maps package by only loading a given map when users are looking at areas and zoom levels appropriate for viewing specific map features. We also use these tags to display photos and orientation symbols only when users are zoomed in close to the ground surface (e.g., Figure 4A). This alleviates the problem of unnecessary clutter in the viewing window when zoomed out to a wider field of view. Note that the individual map KML files are loaded with the tags that are coded after the tags (Table 2). The Maps Package Viewed within a Web Browser KML and KMZ files can also be viewed in a web page by installing the Google Earth API in your web browser of choice.

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Figure 5. (A) Cross Section Model Generator web page. (B) A series of cross sections displayed above the geologic maps of the Massanutten Synclinorium.

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Figure 6. View of the White Hall quadrangle geologic map in Google Earth showing source information displayed in a pop-up balloon when the quadrangle map is first viewed. From Doctor et al. (2010).

With knowledge of some basic HTML, Javascript, and a free license key from Google (http://code.google.com/apis/maps/ signup.html), a web designer can include a GE window in a web page and load any desired KML or KMZ files. All of the functions described previously in this paper will behave exactly the same within the GE API. See De Paor et al. (this volume, Chapter 6) for a more complete description of similarities and differences between the Google Earth application and the GE API. One distinct advantage to using the GE API is the capability to restrict a user’s ability to wander off task while using custom KML and KMZ files in GE. With some Javascript coding, a menu of radio button selections can be displayed on the same web page as the GE API, so that users can display only those KML files that they desire. Similarly, the JavaScript programmer can make obvious which content is available to users. The current prototype web page for the Virginia geologic maps package: (http://

csmres.jmu.edu/Geollab/Whitmeyer/web/visuals/GoogleEarth/ Virginia/VirginiaMaps.html) has toggle buttons to turn on/off the specific geologic maps and cross sections (Fig. 7). Other less relevant items that are displayed in the Layers and Places windows of the stand-alone GE application are not visible to users, which streamlines and simplifies the maps functionality. Initial informal feedback suggests that novice users prefer the direct, but restricted, GE API interface, while more experienced users of Google Earth prefer to have the full functionality of the standalone GE application. APPLICATIONS OF THE MAPS PACKAGE We envision the Virginia maps package as a useful compilation of geologic information for geology professionals and novices alike. The intuitive design of the maps interface, coupled with

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TABLE 2. KML CODE SNIPPETS FROM THE MASTER VIRGINIAGEOLOGICMAPS.KML FILE THAT USERS DOWNLOAD TO OPEN THE MAPS PACKAGE IN GOOGLE EARTH Virginia Geologic Maps 1 Physiographic Provinces 42.00 34.00 -73.00 -86.00 0 0 100 2000 0 0 http://csmres.jmu.edu/Geollab/Whitmeyer/web/ visuals/GoogleEarth/Virginia/ PhysiographicProvinces.kml onRegion

Virginia Geologic Map and Cross-section 1 42.00 34.00 -73.00 -86.00 0 0 1500 10000 0 0 Virginia Geologic Map http://csmres.jmu.edu/Geollab/Whitmeyer/ web/visuals/GoogleEarth/Virginia/ VirginiaGeologicMap.kml onRegion Note: This master code loads each of the maps in turn depending on the users viewpoint within Google Earth. The tags set the viewing bounds for each map and the tags load the individual maps from an external server. The tag contains source information for the original map. (continued)

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TABLE 2. (continued) Virginia I-64 Cross Section 0 http://csmres.jmu.edu/Geollab/Whitmeyer/ web/visuals/GoogleEarth/Virginia/ I64XS.kmz onRegion



White Hall Geologic Map SOURCE: Doctor, D.H., Orndorff, R.C., Parker, R.A., Weary, D.J., and Repetski, J.E., 2010, Geologic map of the White Hall quadrangle, Frederick County, Virginia, and Berkeley County, West Virginia: U.S. Geological Survey Open-File Report 2010–1265, 1 pl., scale 1:24,000, available only at http://pubs.usgs.gov/of/2010/1265 39.375 39.25 -78.125 -78.25 192 http://csmres.jmu.edu/Geollab/Whitmeyer/web/visuals/GoogleEarth/Virginia/WhiteHall.kmz onRegion … … Note: This master code loads each of the maps in turn depending on the users viewpoint within Google Earth. The tags set the viewing bounds for each map and the tags load the individual maps from an external server. The tag contains source information for the original map.

Google Earth’s search function, should provide quick and easy access to rock types and other geologic data at multiple levels of detail. As examples: (1) industry professionals, such as construction or environmental engineers, could quickly find information on subsurface rock type in a construction or wetland site; (2) professional geologists or advanced students could examine bedding orientations of rock outcrops at locations like the southern end of the Massanutten Synclinorium to determine regional structure (Fig. 4A); or (3) teachers could design a GE Tour to virtually visit outcrops as a preview for an upcoming school field trip. The touring capability of Google Earth can be a powerful tool for illustrating geology to students and the general public. Scripted tours, in which the user starts the tour and the program automatically flies over a terrain, are intuitively appealing for students raised with digital devices. GE Tours can be created with relative ease, incorporating many of the map elements dis-

cussed in previous sections of this manuscript, and then saved as KMZ files. GE Tours can include a narrated audio track as well as text/image balloons that turn on and off as required during the tour. See Treves and Bailey (this volume) for details on creating effective tours in Google Earth. In the geology department at the College of William and Mary tours of the Blue Ridge and Great Valley regions (Fig. 3A) are used to introduce students to the topography and geology of the areas prior to visiting the region on a field trip. Tours can highlight salient topographic features and illustrate the linkage between the topography and bedrock geology. Additionally, tours serve as a springboard for individual student inquiry into a region. Finally, in situations where student access to outcrops is limited by landowner restrictions or individual mobility issues, virtual tours may provide the only way to examine geology in a setting that, in many respects, emulates the natural one.

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Figure 7. The Virginia geologic maps package viewed in a web browser using the Google Earth API. The maps displayed are toggled by the buttons to the left of the Google Earth window, so that several of the Great Valley quadrangle maps are displayed along with yellow 7.5ʹ quadrangle outlines. The region shown is similar to the region in Figure 3B. This web page can be accessed at: http://csmres.jmu.edu/Geollab/Whitmeyer/ web/visuals/GoogleEarth/Virginia/VirginiaMaps.html.

CONCLUSIONS The geologic maps package presented here provides a new, intuitive, digital interface for the investigation of geologic maps and data. The maps package is currently a prototype that focuses on Virginia, and specifically the Shenandoah Valley region of northwestern Virginia. However, it is hoped that this design can be exported to other states and regions to create an integrated continental-scale digital geologic maps package. Applications for this sort of publicly available maps package include quick access to geologic information for geology novices as well as professionals, and custom tours for presentations and inquirybased investigations by students and the general public. This prototype multi-level maps package was developed with collaboration between universities (James Madison University, College of William and Mary), state agencies (Virginia Department of Mines, Minerals and Energy, Department of Geology and Mineral Resources) and federal organizations (U.S. Geological Survey). We envision the expansion of this effort to other states and regions by similar collaborative teams, ultimately resulting in a

continent-wide package of digital geologic maps that are universally accessible. ACKNOWLEDGMENTS This manuscript was improved by comments from Andy Bobyarchick, Jesse Hill, and John Bailey. Early versions of this maps package were improved though comments and suggestions by Declan De Paor, Dan Doctor, Randy Orndorff, and Matt Heller, among others. This work has been partially supported by USGS EDMAP, Virginia DMME STATEMAP, and NSF grants (0837049, 1022782, 1034660). Any opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the USGS, Virginia DMME, National Science Foundation, or Google Inc. REFERENCES CITED Bailey, C.M., Southworth, S., and Tollo, R.P., 2006, Tectonic history of the Blue Ridge north-central Virginia, in Pazzaglia, F.J., ed., Excursions in Geology

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