BUILDING TECTONIC RECONSTRUCTIONS IN GOOGLE EARTH USING A NEW TOOLKIT TO MOVE AND ROTATE POLYGONS

Tectonic concepts are challenging for geoscience novices and the general public to comprehend, as they require the ability to both visualize geologic maps and structures in 3-D, and understand how these features change through time. The potential of Google Earth as a visualization platform for the geosciences is well documented, and the virtual globe interface and timespan feature provide ideal mechanisms for animating geologic and tectonic processes through time. However, to date there has been little development in the use of Google Earth for tectonic reconstructions. This may stem from the absence of tools within the native Google Earth application to move, rotate, or otherwise modify polygons or polylines (paths.) To address this deficiency, we have developed a toolkit to move and rotate KML elements (points, lines, and polygons.) The PERL script operates outside of the Google Earth application and modifies existing KML files based on user-defined parameters, such as distance and azimuth of transposition, angle of rotation, and rotation about an external Euler pole.

We have developed two new tectonic animations in Google Earth using the new toolkit. First, we updated and animated the Whitmeyer and Karlstrom (2007) sequence of tectonic maps of North America. Second, we updated the Li et al. (2007) Rodinia reconstruction, as previously depicted on a 2-D surface using Flash to animate continental plate movement through time (Whitmeyer et al., 2007.) The virtual 3-D environment in Google Earth provides a dramatic improvement over the original 2-D Powerpoint and Flash animations. The 3-D globe removes distortion that resulted from projecting 3-D elements onto 2-D surfaces, although the virtual globe environment can result in the loss of sight of continental elements when they move to the far side of the globe out of the field of view. We suggest that further development of tools to facilitate the modification of KML polygons and other elements will enable even novice users of Google Earth to develop their own tectonic and geologic reconstructions.