How Long do Volcanic Eruptions Last? - John Seach

It is much more difficult to predict the end of an eruption than to predict its beginning. The table below gives the length of time that volcanoes erupt.
Explosive eruptions end when sufficient decompression is attained to cause magma chamber collapse and restoration of the initial pressure conditions.

Length of Eruption

% of Eruptions

Cumulative Total %

< 1 day

10

10

1 day to 1 week 

14

24

1 week to 1 month

   20

44

1 to 6 months

  28

72

6 months to 1 year 

   12 

84

1 to 2 years 

   7

91

2 to 5 years 

  5

96

5 to 10 years 

  2

98

10 to 20 years

   1

99

> 20 years

  1

100