How would an eruption of Mount Rainier compare to the 1980 eruption of Mount St. Helens?

Eruptions of Mount Rainier usually produce much less volcanic ash than do eruptions at Mount St. Helens. However, owing to the volcano's great height and widespread cover of snow and glacier ice, eruption-triggered debris flows at Mount Rainier are likely to be much larger -- and will travel a greater distance -- than those at Mount St. Helens in 1980. Furthermore, areas at risk from debris flows from Mount Rainier are more densely populated than similar areas around Mount St. Helens. 

Learn More:

Living with a volcano in your back yard -- volcanic hazards at Mount Rainier

Debris Flows at Mount Rainier

Mount Rainier Summary & Quick Facts

Mount St. Helens Summary & Quick Facts