Can the inextinguishable flames of Amaterasu burn the Amaterasu cast by another user? Will they both cease to exist or burn forever?
To first answer this question; we must first look into "What can turn off Amaterasu"
- Amaterasu lasts 7 days and 7 nights
- Amaterasu can be turned off by the user's will
- Amaterasu is turned off when the material projected onto it has been burned
With that being said, Amaterasu 2 will not "burn out" Amaterasu 1, they will simply burn for 7 days and 7 nights before they will both cease to exist.
Here you can read more about Amaterasu