Classical "hard copy" geological maps have always been 4-dimensional to the expert eye. The shapes of bedding traces, rules of "veeing," and standard topographic surface patterns subconsciously convey the 3-dimensional form of strata and structures even where there are no isopachs or structure contours. Stratigraphic superposition, contact offsets, and cross-cutting relationships reveal the dimension of time. Despite its intellectual and artistic appeal, however, the traditional geological map suffers from limitations, both theoretical and practical. Except for insets, the scale is uniform across a map even though the density of controlling data may vary locally by orders of magnitude. Cross-section balancing constraints are not generally applied to the map plane. The current topographic surface is often an inappropriate reference base; paleogeology needs to be projected onto paleogeography! It can be difficult to subject a tectonic model to hypothesis testing due to the disconnect between a map and the supporting field and laboratory data. Even closely related topics, such as structure and metamorphism, are frequently presented on separate maps. Finally, hard-copy maps are, by definition, dated.

Key features of interactive 4D digital maps include scale zooming, data draping, data merging, layering, transparency, linking of map data to external sources, real-time monitoring and updating, and wiki-style authoring. Since 2005, a new revolution is in progress with the development of Google Earth™ and similar internet-based digital map tools. It is now possible to visualize a single, highly layered, multi-dimensional, deeply zoomable, geological map of the Earth.