Geography university essays?

The department should make the marking criteria available somewhere. Try reaching out to one of the geography students on the course otherwise?
That said generally at degree level there isn't a specific "format" you need to approach essays with (other than generally needing an intro, main body, and conclusion, and proper referencing - although the latter may or may not be needed for a timed exam based essay - you should definitely check this!). You don't need to use a rigid internal structure for your essay (and it's probably better not to) as long as you directly answer the question with a sustained argument well supported by the relevant literature.
I found the essays I've done best in this year (different subject area(s) also at UCL) were the ones I found a kind of "hook" into it as that let me keep coming back to that main point I was arguing for. As that helped me avoid just falling into the trap of sort of generic "exposition" of factual material without much analysis.

There's a vague rubric that talks about understanding of the content, level of analysis, grammar etc. but no guidance on style on structure, or expectations for referencing. I also don't have access to the department moodle page itself (like I have for my own programme) since I'm only taking that one module. Unfortunately i don't know anyone on the course and even if i was able to reach out to any i wouldn't be hopeful for a response, got a lot of side eye and being ignored for being from a different department during the lectures and seminars 😅 Thanks for your guidance on writing it, that's kind of a relief that it seems to be fairly similar and I'll keep it in mind!