``For the last decade or so we've not really seen that at all. The last explosive eruption was in early 2001,'' Ms Jolly said.
From 1976 to 2001 White Island was ``very, very active'' with ``a lot of ash coming out and small explosions''.
``We've had a decade [of rest] and now it seems as though it's starting up again,'' Ms Jolly said.
Two walking tracks near Mt Tongariro are expected to open today though it is too early to say when the popular Tongariro Alpine Crossing will reopen, the Department of Conservation says.
Scientists flying over Mt Tongariro will try to pinpoint exactly where the eruption, which spewed ash and rock high into the air, came from.
Volcanologist Steve Sherburn said GNS Science would draw a hazard map for people working or visiting the area.
``One of the hazards is what we call ballistics, basically big rocks. We usually define a roughly 3km radius around the crater for the typical distance these things can fly,'' Mr Sherburn said.
``That's obviously a really high hazard, because if one hits you and it is more than about a pea-size, it will probably kill you.''
Mr Sherburn said what the earthquake would do next was anyone's guess.
``This is the question that we simply do not have an answer for, particularly when volcanoes are in a period of waking up they can have an eruption and then do nothing for days and weeks and then gradually build up over time, or it could be something like the Ruapehu 2007 eruption or Raoul Island 2005 eruption which were just one-shot wonders.''
-APNZ
