Dear Geologist - I regret that I am going to disagree with my colleagues on this question. I am replying as a private pilot license for 37 years. I have not had FAA problems myself, but I know people who have run a-foul of the FAA. The FAA has a black-and-white view of the world. If the FAA can find an interpretation that disadvantages the pilot in a conflict, they can and will pick that interpretation. Unless there is case-law which supports the position that an image developed under recreational rules is later used for compensation, I think you want to go into this with your eyes wide open. First, I honestly believe that your risk is very, very low. Enforcement appears to be almost non-existent. Second, I think, you should decline photo credit, since that could qualify as indirect compensation. So, I think, you are mostly safe, but your are not completely free and clear, in my opinion.
For a licensed pilot, the Part 107 test is very easy. But, for a person not familiar with aviation, it is not a piece of cake. If you like doing this kind of imaging, study the rules and take the test. You might like getting credit for what you are doing!