In this contribution we consider the visualization of global, deep Earth volume datasets for display and researcher interaction. While the algorithms and data analysis techniques that produce such volumetric results have become more sophisticated, the manner of visualizing these findings can be improved. We address the challenge of making an illustrative, exploratory visualization of a global geoscience dataset using a combined seismic tomography result, the primary means by which geoscientists infer structure and process in the deep Earth. We present a novel, interactive graphical application suite and associated workflow that uses an intuitive 2.5D layer compositing approach. This allows the user to adjust the separation between data-slices, control graphics variables such as color mapping, opacity and compositing, and facilitate exploration and annotation of the architecture of the lithosphere. Graphics outputs from our applications are enabled for immersive systems such as dome displays. In a case study we visualize the deep Earth structure beneath the Indian Ocean region. We anticipate that the application methodology will find use in the visualization of multiple datasets representing aspects of the Earth's deep interior and atmosphere, and in the interaction with the increasing number of rich datasets from missions to our neighboring planets.