I hate to mention this, but Mt. St. Helens was a rather small event on the geologic scale. Even the deadly tsunami was moderate at most. We are overdue for several events expected to be truly GLOBAL cataclysms. The most significant in the US is the Yellowstone super volcano. It could be today or 50,000 years from now since even a million years is a rather short blip on the geologic time scale. Of course, I consider that scale to be grossly inaccurate, but it's handy for relative dating.IT is such a mind twister to consider these various natural calamities, like earthquakes, Catrina sized weather and others. They occur over large areas, or pinpoint with-in the same and to sort periods within a wide spread of time. The northwest is nearly covered in 30 to 90ft of pyroclastic material. How is that? Well, every 200 years or so something 'large' happens in the northwest. That would place about 50 events inside of 10,000 years. Imagine 50 events as big or bigger than Mt St. Helens.
With those events a small segment of the population suffers greatly. But the larger part is relatively unscathed. It's a tuff proposition to figure out how much you should do to secure your self. In hind sight, those 70 people that didn't leave the Mt ST. Helens really should have. The mud-flows afterward had a bigger effect on the population in general.
I think comparing that to what happened in Mexico city killing 25k people, and the tsunami that killed 200,000 shows it's very worth while to be aware and prepared. On the other hand these casualties are less than a drop in the bucket compared to a world of over 5billion.