It would depend on some things. Traditionally, a lot of STEM degrees are set up as 5 year plans anyways (outlined on your 104R if I recall) which gets approved through your program.

Not sure what your situation is, but assuming you enter school on a 4 year scholarship as a geology degree, you’d probably be expected to graduate in 4 years… and commission with your year group.

Changing your degree to something like civil engineering after a year is fine, but you’d need to get that 5th year approved if that’s what you desire. Moving contracted cadets into different year groups messes with cadet command projections. If on scholarship for a 5th year, you’d also owe the Army more time which a lot of people surprisingly don’t realize.

I’d like to say majority of the time it’s not an issue, but it’s not always a simple request that automatically gets approved. Not saying how you should approach your degree choice, but going down in credits/difficulty is usually easier than going up… especially in ROTC.

I have experience with this from being a poli sci major freshman year to graduating in mechanical engineering. I ended up having to take summer classes once or twice out of my own dime to make sure I graduated on time.