Within New Zealand is a tall volcano known for its snow covered peaks and near perfect
circular shape.
What I am referring to is Mount Taranaki, which last erupted only 200 years ago.
Taranaki is the second tallest active volcano in New Zealand, and has produced a number
of very large recent eruptions.
As such, it may only be a matter of time before it erupts again.
This video will discuss this volcano, and mention what its future hazards are.
Mount Taranaki is located near the southwest corner of the north island of New Zealand.
Specifically, it is 19 kilometers west of the city of Stratford.
As we zoom in, you will note a circular forest surrounding the volcano.
This is not an artefact caused by satellite imagery, but rather due to preservation, as
it represents the boundary of Mount Taranaki National Park.
Mount Taranaki began forming 130,000 years ago, when magma related to a weak point in
the crust which had constructed two other regional volcanoes reached the surface.
The lava which was ejected onto the surface erupted in a manner called a vulcanian eruption.
During this style of eruption, highly viscous lava piles up onto a central vent.
Then, pressure builds up beneath the vent, and it creates a moderately sized explosion.
This cycle of events then occurs every 6 hours.
Over time, these eruptions built Taranaki to a height of over 1500 meters via overlapping
layers of both lava domes and ash.
Unlike other similar stratovolcanoes, 99% of eruptions from this volcano occurred from
a central vent.
As a result, Taranaki continued to be built with a near perfect rounded cylindrical shape.
However, this caused the volcano to have much steeper slopes than an average volcano, leading
to high amounts of structural instability.
Eventually, the slopes were too great for the underlying rock to handle, and the volcano
partially collapsed in a massive eruption.
During Taranaki's geologic history, we know that at least a half dozen, if not more, of
these collapses have occurred.
The last of these major collapses occurred 7500 years ago, and left behind a major scar
on the SW of the mountain.
In the aftermath of this major eruption, several isolated lava domes formed within a few kilometers
of its summit.
One of these lava domes is called the southern beehive, and formed during an eruption in
1250 BC. 3,000 years ago, lava suddenly erupted on
the southern flank of Taranaki, and began to form a new volcanic cone.
Over the course of the subsequent 1500 years, numerous eruptions built this volcanic cone,
called Fanthams peak, to a height of 1966 meters.
Afterwards, this volcanic cone became largely inactive, and eruptions moved back to Taranaki's
main summit.
In the last 1,000 years, Taranaki has erupted 14 times.
Many of these eruptions were quite large, rating as between a 3 and a 4 on the volcanic
explosivity index.
The last of these eruptions took place in 1800.
However, there is also unverified but reputable reports of an eruption in 1854.
If there was an eruption in that year, it was likely relatively small in size and created
a small lava dome on the mountain's summit.
Today, Mount Taranaki lies dormant, but could erupt once again with rather little notice.
The chance of it erupting in any given year is about 1 in 90.
When Taranaki does erupt again, it would create two primary hazards.
One of these hazards are pyroclastic flows, which are a mixture of hot ash, lava fragments,
and gases which hug the ground and quickly travel downslope during explosive eruptions.
Two hazard zones have been mapped in the event of a future eruption.
The outer edge of these had a radius of about 16 kilometers, and represents the furthest
extent pyroclastic flows have traveled in the last 130,000 years.
The inner radius represents a parcel of land which has been frequently covered by these
in the last 10,000 years.
The second hazard is lahars, which are could effect a number of distant communities.
When ash is quickly washed downhill, it creates a phenomena similar to a flash flood.
These lahars would travel dozens of kilometers along riverbeds in the area.
Here is a map of areas which could be effected by future lahars.
I hope that you enjoyed this video.
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