Question

EXERCISE 5.15 Stratovolcano Disaster Case Histories (continued) Name: Course: Section: Date: Using the figure from the previous page of the timeline and nature of significant eruptions at Mt. St. Helens as a reference, answer the following questions: What is the average number of years that the volcano has remained dormant between eruptions on period?__ (e) Does the active/dormant cycle appear to be regular or erratic (1) Suggest a geologic explanation for this pattern ( Based on the average dormant interval following significant eruptions, predict when the next significant eruption is likely to occur. (h) What factors make such predictions difficult and sometimes inaccurate? How do the 2004 eruption and 2017 earthquake swarms affect your prediction?

Answer 1

D. As per the figure showing the eruptive history of Mt. St. Helens the average number of years for which the volcano remained dominant for approximately 90 years.

E. The time interval between the active and dominant stage is nearly 80 years and this is almost constant and therefore it’s correct to say that cycle is regular.

F. The reason why it takes around 90 years for volcano to erupt is because during those 80 years the stress accumulate and reaches to a point where it becomes more than the threshold that can be sustained by the subsurface formation and therefore earthquake occurs.

G. As per the history of the earthquake the next earthquake will happen in the year 2030-2040.

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