Geology being a good career is dependent upon the school he chooses and whether they teach theory or application.
DH had a hard time getting a job out of school because he went to a research school and learned great theory and no application. He can identify a fault line at 1/2 a mile, map the geologic history of a piece of land and tell you what kind of rock you've picked up from the ground but you don't get much need for that with most companies out here. Had he gone to a school that teaches application, he would have been much better off. Even though he had a slow start, he is now working for a great company and earning good money. Earning potential as a geologist is pretty good, especially if you pursue professional certifications like "Certified Geologist", etc.
Now if your DS wants to teach, a "theory" school would be perfect for him. DH could teach in a second but doesn't want to deal with the problem kids.
If your DS is interested in the Appalachians, geotechnical is probably a good field for him. Honestly, I would recommend contacting the geology department at your local college. Geologists LOVE to talk about their field and love to share it with kids. I'm sure you would have no problem finding someone to meet with DS and answer his questions.
Let me know if you have any other questions. DH is having a ball answering these!
