I’m a geologist, did natural sciences / earth science at university, then an industry focussed masters, and have worked as a geologist ever since.
Geography, chemistry and maths are excellent choices for a geology degree. Frankly, you can enter a geology degree with quite a range of different A levels, as they teach it from scratch, and just need you to be a good, curious scientist who loves the subject.
There are loads of different strands to geology, and people gravitate to the ones they most enjoy (or the ones they think will have the better career prospects!). I work with lots of geologists who are more at the geography side of things - they specialise in understanding ancient river systems, sand and mud deposition, development of carbonate systems (reefs, chalk etc). Others are geochemists, or rock quality specialists, looking in detail at the ancient fluids within the rocks, or how the rock grains have been affected by complex tectonic and burial histories. Others far more generalised. A lot of these will have an interest in geography (in a way, a lot of geology is basically historical geography). Chemistry is a hugely useful one too - understanding the chemical composition and alterations of minerals and the fluids within the rocks. Maths really really helps, though some geologists are famously rather terrible at maths.
Other geologists take a slightly more numerical approach, they may get interested in a more geophysical angle - how seismic waves move through the earth, calculating and understanding geophysical signals, large scale mantle and volcanic processes can end up in this area too. Maths will get you a long way here, but I think for this sort of thing, physics is a huge help to get into it. Physics is always a great thing to do - but there are whole massive areas of geology that certainly won’t need it, especially if you’ve kept maths up.
The sixth form tutor may well know plenty of geoscientists with physics, but there are absolutely loads without, and looking at uni requirements, it’s not at all necessary. Those who love physics will find it helpful, but those who love geography, chemistry etc will find those helpful too. You need a full range of backgrounds, one isn’t better than the other.
Finally, someone earlier made the extremely good point that geography is particularly useful here as it’s the only essay-ish subject on the list. This, I would say, is a massive advantage - take an a level that requires you to build up skills in constructing long answers in exams, coursework etc. I actually did English lit a level alongside maths, chemistry, physics, and honestly if it wasn’t for eng lit, I’d have found the essay-style geology questions in my uni exams and coursework FAR harder. You’ll be writing essays comparing the research of several people who have all investigated eg crystalline deposition in magma chambers, or development of clay minerals under pressure, etc etc, and you need to be comparing and contrasting, understanding papers, drawing conclusions, citing sources. Geography will be excellent training for this, more so than physics.
Also, on a different note, quite a few people would do a more generalised undergrad degree (eg geology) and then an environmental geoscience masters afterwards. That’s always an option. (Though more expensive).