Science takes centre stage at active Mount Ruapehu

Our Science

01 July 2022

Karen+Britten hero rua

Tremors, volcanic gas and rising temperatures – the continuing story of volcanic unrest at Mt Ruapehu.

Over the past four months, the active cone volcano Ruapehu has kept GNS Science volcanologists busy monitoring volcanic tremor, gas emissions, the crater lake temperature and interpreting what the fluctuating activity might mean. Ruapehu means ‘pit of noise’ in Māori. It is an apt name given this frequently active volcano is speaking to us, telling a story that our scientists work hard to understand.

In early-March the GeoNet Volcano Monitoring Group detected an increase in volcanic tremor levels at Mt Ruapehu, accompanied later by a rise in Crater Lake (Te Wai ā-moe) temperature and an increased output of volcanic gas. 

Ruapehu Volcanic Unrest Update - April 2022 transcript
0:03
At Mount Ruapehu since mid March, the level of tremor or type of volcanic earthquake,
0:08
as well as the temperature of Te Wai ā-moe crater lake have been increasing.
0:12
We've also seen increases in gas levels from the volcano.
0:16
Correspondingly, we raised the volcanic alert level, to volcanic alert level two, which
0:21
is the highest level before the volcano is in eruption, and it's consistent with moderate
0:26
to heightened volcanic unrest.
0:28
Over the past week, volcanic activity has continued to increase, putting the unrest
0:33
status firmly in the heightened unrest category.
0:37
Volcanic tremor and volcanic gas have both continued to increase.
0:41
Carbon dioxide levels are at the second highest level that we've recorded since records began
0:46
in the early 2000s.
0:50
The temperature of Te Wai ā-moe crater lake is now at 38 degrees Celsius.
0:54
The sustained nature of the unrest of the volcano is different to the typical start
0:58
of a heating cycle.
1:00
The level of gas and the level of tremor at the volcano at the moment indicate that magma
1:06
could well be interacting with the geothermal system inside the volcano.
1:12
The most likely outcome of the current unrest episode at Ruapehu is that there will be
1:17
no eruptive activity.
1:19
This is consistent with unrest over the last 15 years, which have also had no eruptive
1:24
activity following them.
1:26
There is the possibility of one or more eruptions impacting the summit area of Ruapehu, and
1:31
also putting lahars into catchments, particularly the Whangaehu valley.
1:35
This might be similar to the eruption of September 2007.
1:39
The chance of a larger eruption like some that occurred in 1995 to 1996 has increased,
1:45
but remains very unlikely.
1:47
That's the scale of eruption that might put out more widespread ash.
1:51
We expect an eruption of that scale would probably occur after a sequence of smaller
1:56
events, mainly due to the presence of a crater lake.
1:59
It's important to remember that Ruapehu is an active volcano,
2:02
and it can erupt at any time.
2:04
with little or no warning.
2:07
The national emergency management agencies 
2:10
get ready website has information  to help you understand
2:13
what to do before, during and after a volcanic event.
2:18
As of today, the 13th of April, there was a two kilometer exclusion zone from the center
2:23
of crater lake.
2:24
But that could change.
2:26
It's important to look to the Department of Conservations website and social media pages.
2:30
If you're planning on heading to Tongariro National Park to get the latest risk information
2:34
and what to do.
2:35
We continue to monitor the volcano and conduct 
2:38
regular gas flights to  understand what is happening.
2:41
We will update the status of the volcano through volcanic activity bulletins, the geonet website
2:47
and app.

Ruapehu Volcanic Unrest Update - April 2022

GNS Science Principal Scientist Graham Leonard provides an update on what is happening at Ruapehu volcano this month and what future activity could look like.

The number one question we are trying to answer is: will it erupt? Which is complex science

Brad Scott Science Volcano Information Specialist GNS Science

Helping to answer that question is a team of GNS scientists based at Wairakei and Avalon, who undertake extensive monitoring of more than 10 active and inactive volcanoes across New Zealand. 

Reflecting the elevated volcanic unrest, the Volcanic Alert Level was raised to Level 2 on 21 March. GNS scientists also began carrying out more frequent aerial gas measurements and Crater Lake (Te Wai ā-moe) sampling as weather allowed. 

As the weeks went on, so too did Ruapehu’s story. 

The volcanic tremors became stronger, the lake heated up and record-breaking amounts of gas emissions were measured. The volcanic unrest was intensifying, moving from moderate to heightened unrest. The sustained nature of the volcanic activity being detected indicated that magma (molten rock) may be rising within the volcano. 

Volcanoes are complex and scientifically we still haven’t found the magic bullet that accurately predicts an eruption. We are able to recognise changes in the volcanic unrest that may lead to an eruption, and this is what motivates our volcano monitoring team,

Brad Scott Volcano Information Specialist Brad Scott GNS Science
Illustrative diagram showing what is below Mt Ruapehu
Illustrative diagram showing what is below Mt Ruapehu. Credit: GNS Science

“The seismic data, gas and water chemistry we gather can tell us a great deal about what a volcano is doing, but that is at a point in time. Our interpretation is that unrest is derived from a relatively shallow magma body, which is thought to currently exist a few kilometres beneath the crater lake.”

“The temperature of the crater lake typically ranges from ~12 °C to ~45°C, over periods of up to a year, and these temperature cycles have occurred many times over the past 15 years. During this recent period of unrest, Crater Lake (Te Wai ā-moe) temperature rose to 41°C at its peak.” 

At the same time, the volcanic tremors remained elevated above the typical background levels scientists record at Ruapehu. In fact, tremors recorded through the duration of this period of unrest are the most sustained and vigorous of those recorded in two decades. 

While Ruapehu has not erupted since 2007, it is frequently active and has the potential to erupt with little or no warning when in a state of volcanic unrest. 

The temperature of the lake has dropped recently and stabilised at around 22°C, but our Volcano Monitoring Group assisted by our National Geohazards Monitoring Centre continue to closely monitor the volcano for further changes in activity. 

With public safety front of mind, the Department of Conservation provides up to date information on access to the Mt Ruapehu area and volcanic risk in Tongariro National Park. 

GNS makes available regular updates on the status of the active volcanoes in New Zealand via Volcano Activity Bulletins (VABs). Live monitoring data can be seen on the GeoNet website.

Find more content related to:

GNS Science areas
GNS Science topics

By continuing with this download you agree to abide by the rules laid out in the Terms and conditions/Terms of use listed on this page.

If there are no specific Terms and conditions/Terms of use listed then please refer to our Copyright and Disclaimer page and Privacy Policy page

Download