How to detect if the camera is below the landscape

I have a Voxel landscape - the basic premiss of my project is that the player controls a tank and that tank shoots - they can destroy enemies and also if they miss their missile will create a creator in the ground - like this

There will also be an element to the game where the player can go ‘mining’ using the blast from their turret to create tunnels like so

What I would like to do is when the player camera is ‘underground’ I would like to change certain elements like reduce the camera bloom and exposure etc

So what I thought would be a sensible approach would be to have a post process volume under the landscape and if they players camera is below the landscape then apply these settings

I’d also like to make other elements appear / disappear based on that

Does this sound like a sensible approach, is there a better way to achieve my goal?

Hello developer that is a great atmosphere looks awesome man, great stuff