How to determine quickly what is the currently running OS volume? Is there a quick way to find the volume on which is located the current running OS ? I've noticed that the sort order of the volumes list can be changed manually, so the current system volume is not always on the top of the list. 

PS : And, in my case, of course, there are several volumes with a System Folder.
If in terminal, one could type open / which opens a Finder window for the root (similar to what @andersmoldin described).

You could also drag the volume's icon to the Finder's sidebar for quick access later on.

Or you could drag it to the Dock.