Immersive 3D worlds can be designed to effectively engage students in peer-to-peer collaborative learning activities, supported by scientific visualization, to help with understanding complex concepts associated with learning science, technology, engineering, and mathematics (STEM). Previous research studies have shown STEM learning benefits associated with the use of scientific visualization tools involving model-based reasoning (MBR). Little is known, however, about collaborative use of scientific visualization, via MBR, within an immersive 3D-world learning environment for helping to improve perceived value of STEM learning and knowledge acquisition in a targeted domain such as geothermal energy. Geothermal energy was selected as the study's STEM focus, because understanding in the domain is highly dependent on successfully integrating science and mathematics concepts. This study used a 2x2 Mixed ANOVA, with repeated measures, design to analyze collaborative usage of a geothermal energy MBR model and its effects on learning within an immersive 3D world. The immersive 3D world used for the study is supported by the Open Simulator platform. Findings from this study can suggest ways to improve STEM learning and inform the design of MBR activities when conducted within an immersive 3D world. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]