Why do magma erupt only sometimes explosively?
I am doing some experiments to answer this question.
How?
I am doing decompression experiments using shock tube type apparatus.
A rapid decompression might cause an explosive eruption, and I am
simulating this process.
What determines the eruption styles?
According to my experiments, pressure difference DP and
vesicularity phi are important.
I show you a movie how these two parameters are important.
Movie
This movie shows the response of bubbly fluid to a rapid decompression.
From the top
large phi & large DP
large phi & medium DP
small phi & medium DP
large phi & small DP
negligible phi & medium DP
See?