A lot of Earth science jokes are puns (you’re full of schist; meet me behind the outcrop, baby, I’m a little boulder there; etc.). Here’s the only one I know that pokes fun at fellow Earth scientists.
The university’s geological sciences department decides to add a hydrogeologist to the faculty. They call in a likely candidate to interview with the three faculty members most likely to become close colleagues - a geochemist, a geologist, and a geophysicist.
First the applicant meets with the geochemist. They have a nice chat, and then the geochemist says, “So, do you have any questions for me?”
The applicant says, “Yes. Can you tell me please, what’s 2 + 2?”
The geochemist replies, “Well, of course it will depend on instrument calibration and measurement error, but I’d say 2 + 2 = 4.0000 +/- 0.00000000…”
Next the applicant meets with the geologist. They have a nice chat, and then the geologist asks, “So, do you have any questions?”
The applicant says, “Yes. Can you tell me please, what’s 2 + 2?”
The geologist thinks for a moment, and then says, “Hmm, I’ll say it’s somewhere between 3 and 5.”
Finally the applicant meets with the geophysicist. They have a nice chat, and then the geophysicist asks if the applicant has any more questions.
The applicant says, “Yes. Can you tell me please, what’s 2 + 2?”
The geophysicist leans across his desk, winks and whispers, “What would you like it to be?”