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Will it Bang, Bubble, or Fizz?
Shane Cronin – Massey University
Anticipating the next eruption of Mt Taranaki
Clue no: 1 – what’s at the top?
Rock-falls/avalanches<1 km runout
Block-and-Ash Flows(BAF)Can be 15 km runout
What happens when domes fall down?
Photos: G. Lube
Merapi volcano – June 2006
Twin brother of Mt Taranaki
Erupting sporadically since 1994
>150 deaths
June 2006, 20,000 evacuated, 2 deaths
“minor eruption” evidence of it may never be recorded in the geologic recordAster Image
>700 oC “block-and-ash flows”
Photos – T. Wilson
Original Channel Fill
>1 year later
The aftermath – rain-generated lahars
How do we know this from Taranaki?
Blue-Rata Reserve
Taranaki, 15 km from sourceCharcoal
3 m
Example Taranaki BAF
15 km runout2200 m drop
Image T.Platz
Clue no 2: Pumice
Burrell Lapilli – AD 1655
Explosive eruptions – “Plinian”
Map: T. Platz
Other types and sizes of eruption?
Eruption styles
a) Sub-Plinianb) Dome
a
b
Mineral clues – iron oxides
Images: M. Turner
Clue no 3: Pulses of magma “recharge”
Feldspar textures
Images: Platz, Turner
A repeating pattern of eruption episodes
opening pumice eruption
lava-flows and dome building
Repose ( degassing)
next episode
Episode 1
Episode 3
Episode 2
Umutekai – New Plymouth
Clue no 4: Detailed eruption histories
Overall time-smoothed eruption rates
Image: M.Bebbington
Sub-Plinian
Dome
Splitting record into two types
Image: M.Bebbington
Where are we in the cycle?
Conclusions – next eruption at Mt Taranaki
We are in an unusually long (although not unprecedented) lull in activity
The next eruption could take one of three possible general forms:1. Large explosive pumice eruption (last one AD1655) – not likely2. Small explosive pumice eruption3. Lava dome eruption
Both likely types of eruption will begin with collapses from the summit area – intrusion of magma (oversteepening, earthquakes), and vent clearing
Both types of eruption could herald a period of more frequent eruptions to follow
A lava-dome eruption could continue for many years/decades
High
Low
Hazard Zone 1:300yrs1x106m3
Risk of inundation
Anticipated hazards for the start of the “next one”
Image: J.N. Procter