Professor Richard Price describes how New Zealand scientists are rewriting the textbooks on how volcanoes are understood. Studying andesite volcanoes, they have discovered that all volcanoes may not form the same way.
PROF RICHARD PRICE
The standard model for an andesite volcano is that it is related to the tectonic setting. They occur in a particular structural setting where, according to the plate tectonic model, we are getting a process called subduction taking place, and that is where one plate is being pushed down underneath another.
Where our models differ from past ones is that people have focused very much on that deep process, the original source of the magma, and tried to explain the chemistry and the mineralogy and the magmas according to what is happening down there deep in the mantle
Our models are all focused on what happens when those magmas actually reach the crust and they begin to interact with the crust. So if you’re bringing hot magmas out of the mantle and they arrive in the crust, they are going to melt the crust, and that is really where we think that most of the action takes place as far as andesite magmas are concerned.
The model that we have evolved is a departure from the sort of traditional models that you will see in an encyclopaedia for a volcano where it has a big blob of magma at depth and a pipe coming in the bottom feeding magma into the magma chamber and magma coming out the top through a single pipe to the surface.
Our model, which was derived from studying Ruapehu and Taranaki mainly, is that, rather than a single magma chamber, what you have is a very dispersed system and magma starting off down deep in the mantle and working its way through that plumbing system, with batches of magma of different size being stored for different timescales at different levels in the crust, and as they move through that plumbing system, the magmas interact with each other and with the crust.
NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team