will it bang, bubble, or fizz? shane cronin – massey university anticipating the next eruption of...

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