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Interesting comparative table, here:

https://en.wikipedia.org/wiki/Mount_Tambora

(scroll down)

Krakatau’s VEI was 6, however, it’s ash column went up to an astonishing 80 km. Tambora was “only” 43 km. Also, it appears Krakatau was heard much further away.

https://en.wikipedia.org/wiki/1883_eruption_of_Krakatoa

Reading further, I found that duration of the explosion is a factor in determining VEI.

https://en.wikipedia.org/wiki/Volcanic_Explosivity_Index

My guess is that the peak intensity of the explosions at Krakatau was higher than at Tambora, but Tambora’s bursts were more sustained, ejecting more material in total.

Interesting. I just watched a lecture on the Cascadia fault. Did you know that every 500 years, on average, the Juan DeFuca plate does its thing and the last time it popped was in 1700? That leaves us with another couple hundred years before the next big one is due right? BUT, here is the ticker. The southern part-from southern Ore to its end at N CA has slipped every 2 to 3 hundred years. BTW. It slips and the coast will move over 150 feet to the west while dropping some 30 feet. Portland, will move over 6 feet to the west and drop some 4 to 5 feet. EAST of the Cascades, the land will shift 1 to 3 feet and drop a few inches. That fault effects everything to Idaho. They know for a fact that The northwest area of the northwest rotates counter clockwise to the north east for 14 months, then stop and actually slides back to the southeast for a fraction of an inch. Then it continues its 3/4 inch or so travel to the Northeast-and the whole N American plate is moving to the southwesterly direction. They think that the fault is slipping under the land mass and not in the ocean and the discussion is..when does it trigger the big one?
What does this have to do with volcanoes? Well, those volcanoes are connected to that fault and have not erupted in a long while-other than Mount St Helens. They have measured Mnt Hood for example, and it is moving, as are the rest.

My question to that Professor would have been. When the vent system lines up correctly, do they erupt? No doubt those volcanoes vent system might be out of line because of the land mass movements? When I say vent systems I mean weaker down areas from the Peaks where the rock is easily fractured to allow magma to come up. He might answer that if that were the case then there would be a new appearance of a vent someplace else, but, do they know that the rock aside from the original vent systems might be harder and all.

BTW again..the 1883 eruption of Krakatowa-thats how they spelled it by some back then. Was the most studied of any by that time. The Brits really did a hell of a fine job with that.

Krakatau studies by the Brits is truly the father of modern volcanism studies.

The last big eruption of the Long Valley volcano erupted over 100 cubic miles. It is now listed at the USGS as a very high risk of exploding. But, since that eruption there have been many smaller eruptions there. Same with Yellowstone.

Point is..even if they do blow, it most likely will be a VEI 5 or 6 and not the massive blast from the past. Depends on how many vents are opened up.