A few ways I used to think about them were (I haven't read the rules recently...so sorry if this is useless):On 3. c., there's something about "subsurface geometries," but I don't understand what exactly they are. Would somebody mind explaining what these are so I can look into it a little deeper? I just need to know what they are and the gist of it, no need for in-depth explanations. Thank you!
1) Identifying sub surface geometries in different geologic features and knowing how they "work" (this I think is what UTF is suggesting by looking at folds and faults...there might be others). In general, it's good to visualize each geologic structure as planes, lines, and points. So an example question to think about is: Can you spot the planar, linear, and point like aspects of folds? If you want some ideas for geologic *structures* that can be below the surface (sub surface), maybe look at relative age dating diagrams.
2) But this is also a mapping event! You should also know how to map, read, and understand these geologic structures (whether they are below or above the surface...and everything in between).
-The first way you can do this that I know of is with stereonets, which are all about mapping / noting information about geometric features (planes, lines, and points!).
-Another one would be "outcrop patterns" (the shape a structure makes from looking at a "top view" of the ground...you can maybe spot a fold or fault from a map, but how do we know how they look below the ground? How do you even know there is a fold or fault just from looking at a geologic map? This is how!). Note that "outcropping" I think has something to do with being visible on the surface.
-There are also "structure contours" (these are related to 3 point problems...they are contour lines that you use to usually connect the outcropping points of equal height for a single structure/plane)
-Lastly, cross sections are super common (they can be done with simple old topographic maps to see the shape of a mountain, but you can also use them with structure contours to infer how a structure or say a plane looks below ground).