Ruapehu’s Crater Lake – a Window into the Volcano


Mount Ruapehu is one of our most active
volcanoes, and we know historically that there have been eruptions since at least 1970. There’s been over twenty-eight large eruptions during that time and
many many smaller ones. Most historic eruptions of Mount Ruapehu have come
through the crater lake, and a very common artifact of eruptions of Ruapehu is the
production of lahars. Also, Mount Ruapehu is the home to two very large ski fields, so on a nice
day we can have thousands of people skiing on the volcano, or climbing,
enjoying the alpine environment. This creates a hazard because you have the
people and the volcano together, and this makes it important for us to monitor the volcano The presence of the crater lake
gives us a unique opportunity to see inside the volcano, as the geothermal
system associated with the lake carries many messages and signals from inside
the volcano. About once a month, weather permitting, we will visit the crater lake, and collect water and gas samples.
we’ve been doing this on a regular basis since the 1960’s. Today, this is
carried out by the GeoNet team. We collect a large sample from over the active
upwelling areas and the crater lake, and also capture the dissolved gases into
flasks, along with water samples. Here we have samples from the Ruapehu crater lake.
When we bring the samples here we analyse all the different kinds of elements, and
all these elements can tell us a part of the bigger story of what’s going on
just below the crater lake. After we have analyzed the water composition of the
crater lake of Ruapehu, we look at the data. So in the graph here we have
two chemical elements from the lake. We have in red, the sulphate, and in blue, the chloride. Here we can see there were really big changes in the composition of
both elements because here there was a big activity – volcanic activity, and
afterwards, it settled down. Here you can see that there were
not a lot of changes from the chloride composition but you can see some
relatively low, but clear changes in the sulphate composition and it was just
before the hydrothermal eruption in 2006. And in March 2007 there was some increase in
sulphate. So the graph here represents two different stories. At the bottom of the
crater lake, there are deposits of sulphur which are building up continuously. When
both sulphate and chloride increase, this relates to increased activity in
the magma chamber deep below the lake. But if it’s only sulphate that is
increasing when the chloride stays the same, then it is due to the disturbance of
the sulphur deposit at the bottom of the lake. This indicates shallow
hydrothermal activity rather than a deep-level rise of magma. The chemistry tells us
what’s going on in the crater lake and any significant changes can tell us
also that there is an increase or decrease in volcanic activity and if we
combine this data with other data, we can make a decision on the alert
level of the volcano.

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7 thoughts on “Ruapehu’s Crater Lake – a Window into the Volcano”

  1. Emerald S says:

    curious , would the addition of chlorides in drinking water around specific areas have an effect that might travel by air to the water test areas? for ash from forest fires or volcanic debris do have effect upon ice structures. eg. the particles land on ice and slowly form a tiny fracture that would break ice . ~ lack of wording =sorry but hope your group comprehends the scope of the question.

  2. Abitaskew Dataflow says:

    So we use "bucket" technology? Someone needs to get an Arduino for cryin out loud

  3. Jonathan Tan says:

    0:56 Isn't there a risk of static discharge if you grab a line from a helicopter without letting it touch the ground first?

  4. Ifrah Nayeem says:

    they should have written all this in this paragraph cause its so hard to copy from the video

  5. 666MikeRochip says:

    I think it will go up again..just a matter of time…

  6. Lesley Nikora says:

    thats my moutain

  7. isabelle Fallowfield says:


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