These maps combine a planimetric base with an oblique viewing angle of terrain features. The base of a mountain symbol will be correct planimetrically but its peak may be offset by the oblique viewing angle. The pupose of these maps is the depiction of the relationship between the landforms and their geology and geomorpholgy. See Figure 22. 8.0 Block Diagrams Block diagrams are a pictorial method which used to be used primarily for the portrayal of geologic relationships.
Block diagrams show a portion of the earth's surface and crust from an oblique viewing angle.
The origins of the block diagram were from 18th century geological report illustrated with cross sections. Pictorial sketching was added to the section to add realism and relate the surface expression with subsurface geology. See the block diagram in Figure 23 witha cross section on the front edge. Block diagrams are enjoying a rapid phase of development with the advent of computer graphics and surface creation software. The old fashioned geologic block diagram with cross section is now being reformed to display three dimensional shapes within the earth.