I don't know what A levels to pick!!

I want to study Volcanology/geology in the future, but I did not pick geography as one of my GCSEs. I'm changing schools for sixth form (Perse Sixth Form College), and I've picked biology, chemistry, and art as my A-level choices.
I'm a bit worried about my career path as studying volcanos links to geography and I've never studied geography in my entire life.
If being a volcanologist doesn't work out, I'm also in marine sciences (hoping to study in the field of cnidaria).

Do you think I can still study volcanology/geology without geography knowledge/studies?

Look up courses at university in geology and see if geography is needed as in some units you won’t need geography. Make sure you have the right subjects to study at these unis. Also if you can research things related to that field (do an Epq if you can) so you have something to write about in your personal statement.