Here’s what the valley looks like now:

And here’s what it looked like after the 1880 eruption
And here is what it looked like when the geyser was operating – note that the lake has filled in and become a mud-flatYou can just see an observation hut on the top of the L hill.  4 people were killed when they went to watch the geyser from a lower hill – known to be dangerous but they thought they would have a go.  Apparently washed away by a wave of boiling water.