Mt Tongariro rumbled to life for the first time in more than a
century this morning, spewing a giant ash cloud as far as
Napier. Dr Thomas Wilson, a disaster management lecturer at
Canterbury University, explains all you need to know about the
eruption, its aftermath and what the future may hold. What type
of eruption was it? There are three main types of eruptions you
can get in an explosive event. There's what we call a phreatic
eruption, or steam-driven eruption. This is where water has been
superheated by magma under the volcano, but it's only the water
that erupts in an explosive manner. Basically the hydrothermal
system underneath the volcano erupts, and this is what seems to
have occurred on Tongariro. Another type is a phreatomagmatic
eruption, where water has come into contact with magma and
caused the magma to fragment in an explosive eruption. Then
there's a magmatic eruption, where there's no water interacting,
and it's just the magma erupting itself. Scientists [from GNS]
are out collecting ash s