This is a linkpost for http://www.bbc.com/future/story/20170817-nasas-ambitious-plan-to-save-earth-from-a-supervolcano
This is assuming the danger from unknown unknowns is large. Speaking as a non-expert, i would guess that it is.
Both the chance that the the supervulcano erupts within the next 100 years and the chance that it's more likely to errupt with this project in place are known unknowns.
Why do you assume the danger from unknown unknowns is large?