In the early hours of the morning of June 10th 1886, Mount Tarawera erupted.
And part of that eruption occurred where the pre-existing Lake Rotomahana was.
Now when you bring magma up underneath a lake body
and the magma interacts with water, it's a tremendously explosive eruption,
so there was devastating results with mud, debris and ash flung far and wide
covering many places with up to 10 metres or more of mud.
This project was all brought together to try to see if we can solve the mystery
of what happened to the lake and the Pink and White Terraces
immediately after the eruption.
The focus of this particular project was the AUVs (Autonomous Underwater Vehicles)
They can be programmed to go exactly where we want them to go
at what depth, at what part of the lake, and they're packed with sensors.
Some of these sensors will determine what the topography is down there,
other sensors were looking for rocks or sediments,
other sensors tell you temperature, or the acidity of the lake and so on.
So we're measuring about nine different parameters at the same time.
On a typical day, the guys have to set up the vehicles,
they're mission needs to be programmed into them,
they have to make sure they're ballasted correctly.
Amy, one of the scientists from Woods Hole Oceanographic Institution,
she would control these vehicles.
This is the Remus control van controls where we're monitoring the progress
of the two AUVs that are in the water.
So we are getting through a radio connection to our computers, a status update
on both vehicles every five to seven minutes or so.
The information that's being sent from the vehicle to us,
displays updates on our computer screen here.
This is a vehicle control display
where it shows us the time that we receive the message,
the status, so the role and position of the vehicle,
and then here's our bathymetry map of Lake Rotomahana,
if I undo the map overlay, you can see our track lines.
This track line is showing the vehicle we just deployed,
and you can see that it's plotting itself with these red cross hairs along where we told it to go.
She would monitor that they're doing what they meant to be doing, that everything's fine.
And the vehicle, if it didn't like anything, would send a signal back to her,
and so that you and rescue it.
There were two AUVs, each of which came from Woods Hole
and was developed by scientists at Woods Hole.
And they would have relatively separate jobs to do.
One of them for example had a multi-beam on it,
so it's looking that to map the lake floor.
The other one had a Side Scan Sonar on it to look for the differences
between rocks and sediments and so on, so it could easily detect those.
Each did nine missions, and between them they covered 50 kilometres
of track within the lake, which is on the 6.34 kilometres at it's longest point.
In addition to what was being done by the AUVs at the bottom of the lake,
we had scientists going around the lake, on the lake shore, collecting all sorts of information.
That included measurements of gravity, measurements of magnetism,
and also collecting a number of rocks that were representative of this eruption.
We also had a number of teams doing different operations on the lake surface itself,
this included towing a magnetometer and measuring the magnetic field.
Results from the magnetic survey show us
where we have high degrees of magnetism, where colour's in red.
These are rocks that are still relatively magnetised,
and they've probably not seen a lot of hydrothermal fluid.
By contrast, when we see the blues, the blues tell us
that there's been a lot of hydrothermal fluid pass through here,
and effectively, it's a window into the past.
So this is telling you about the pre 1886 geothermal system
which was quite big, about two by three kilometres
but when we plot on top of this map where the existing discharge
of the hydrothermal fluids are today,
there's a very large new geothermal system in the southern part of the map
where it butts against the red magnetised rocks.
Sharon Walker of NOAA was one who was looking into some the physical properties
that we found within the water column.
My job in this project is to help take measurements in the water
and try to relate what we find in the water
to where it might come from on the lake bed.
This whole screen represents what I was looking at while I was out on the lake yesterday.
The blue line shows the temperature from the surface to the lake down to the lake bed,
and you can see that it's warmer surface, at about 20 meters deep it gets much colder,
22 degrees at the surface to about 14 degrees here,
and then it stays about that temperature all the way down towards the lake bed.
The green line represents how cloudy the water is,
and you can see there was much more cloudiness on the surface
and then a little bit more clear, but then at the bottom, the cloudiness increases again.
This is the range we're really interested in,
because the particles, or what makes the water cloudy in this section
is probably related to what the hot springs are putting into the lake.
One of the most outstanding results from this project
is the detailed bathymetry that we got from one of the AUVs
and we can see and recognise parts of the pre 1896 eruption lakeshore in this data,
so that tells us that some parts of this lake were not modified by the eruption.
An example of that is in the region where we believe the Pink Terraces used to exist prior to the eruption ,
you seen this distinct little arcuate shaped spit coming out in the bathymetry,
now we can absolutely correlate that with pre 1886 eruption photographs of the lake shore,
there's no doubt about that whatsoever.
Once you see where the spit is, you can see just down to the south of it, there are the Pink Terraces.
Then what we did is that we drove the Side Scan vehicle over this particular area
and it revealed these incredibly hard reflectors in the exact position where the Pink Terraces should be.
And we zoom in and look at this up close, you can see these
wonderful arcuate crescent shapes of the terraces,
we know they're standing one to two metres tall because there's an acoustic shadow behind them,
and you can even see what appears to be round holes where the pools would have come
and the hot fluid would have come up and emptied over the side of the terraces.
The last thing we did in this whole process was to lower a camera down
over where we saw these hard reflectors from the Side Scan data
and we put the cameras right down on the lake floor adjacent to these structures,
and we found them to be white, we found them to be very hard,
and they had vertical bulbous faces,
and there's no doubt in our minds that we have captured here
some remnants of the Pink Terraces.