The resulting Fish Canyon Tuff has a volume of approximately 1,200 cubic miles (5,000 km3), giving it a volcanic explosivity index rating of 8.

[7] By contrast, the most powerful human-made explosive device ever detonated, the Tsar Bomba, had a yield of 50 megatons, whereas the eruption at La Garita was about 5,000 times more energetic.

The asteroid impact responsible for that mass-extinction, equivalent to 100 teratons of TNT,[9] was approximately 420 times more powerful than the Fish Canyon eruption.

The Fish Canyon Tuff, made of dacite, is uniform in its petrological composition and forms a single cooling unit despite the huge volume.

The Pagosa Peak Dacite has been interpreted as having erupted during low-energy pyroclastic fountaining and has a volume of about 50–70 cubic miles (200–300 km3).