Visualizing and Understanding Tectonism and Volcanism on Earth and Other Terrestrial Bodies

VISUALIZING AND UNDERSTANDING TECTONISM AND VOLCANISM ON EARTH AND OTHER TERRESTRIAL BODIES Mladen M. Dordevic Old Dominion University, 2013 Co-Directors: Dr. Declan De Paor Dr. Jennifer Georgen This dissertation presents new methods of visualizing, teaching, assessing, mod­ eling, and understanding tectonics on Earth and other celestial bodies. Tectonics is the study of planetary lithospheres and includes impact, plate, plume, cryoand gravitational mechanisms. This dissertation is concerned with plate tectonics and plate/mantle plume interactions. Plate tectonics describes the mainly horizontal motion of lithospheric plates over the asthenosphere. Lithosphere is created a t ridges and consumed a t subduction zones. In addition to the plate tectonic system, mantle plumes also contribute to mass motions in the subsurface Earth. Both plate tectonics and plume upwelling processes help shape the present form of the planetary surface, including long volcanic island chains, deep ocean basins, and plate boundary triple junctions. Better understanding of these processes by visualization and numerical modeling is one of the primary goals of this study. In the geospatial analysis lab at ODU, our research methodology starts with the creation of visualizations for teaching. These include Google Earth-based virtual field explorations enhanced with digitized specimens find emergent geological and geophysical cross sections. We test these in classes with IRB compliance and some­ times this leads to the discovery of tectonic research questions which we then explore. Settings studied in this investigation are Tonga Trench in the western Pacific Ocean, Artemis on Venus, the Hawaiian-Emperor seamount chain, and the Azores triple junction. Some of these cases pose specific geophysical problems that were selected for further study. The Tonga Trench is a subduction zone that includes trench rollback and opening of a marginal basin-the Lau Basin. The rollback process is difficult to imagine, find therefore we created a set of instructional resources using COLLADA models and the Google Earth Application Programming Interface (API). Animated models for the Tonga Trench and Lau Basin helped explained rollback as shown by our outcomes assessments tests and exploration of different initiations of the subduction process led to a new alternative hypothesis for rollback. Virtual field explorations required the development of new interface features for the Google Earth API. All these instructional materials were combined into modular multi-user virtual field trip experiences and were subject to IRB-compliant evalu­ ation of learning outcomes. Animated COLLADA models for the Hawaii Islands and Emperor Seamounts helped explain the origin and time progression of the island chain. Prom seismic data, a three-dimensional reconstruction of the Hawaiian man­ tle plume was created raising the question of the horizontal advection of the plume conduit in the mantle and its correlation with the change in trend of the islands. The Hawaiian-Emperor chain on Earth is spread out as the Pacific plate is moving over the Hawaiian mantle plume. On Venus, however, the Artemis structure was able to grow to super-plume size due to the absence of plate motion. For Venus, visualization was done on a much larger scale, including cross sections of the whole plate showing large plume structures, and Magellan SARS imagery of surface features. In the Azores triple junction, dispersion of plume material is influenced by plate boundary geometry, creating anomalies in seafloor geophysical data for severed hun­ dred kilometers away from the plume center. To explore the interaction between a memtle plume and a plate boundeiry triple junction, a series of three-dimensioned finite element numerical models was calculated. A parameter space investigation changed the location of the plume conduit and its volume flux, as well as the treatment of viscosity. Flow patterns, dynamical topography, relative crustal thickness variations and waist width scaling relationships resulting from these calculations give valuable insight into the importance of triple junction configuration in the dispersion of plume material.