Buckle up for some geology! Now that you’ve seen what it takes to get to the top of a 2518m high volcano, let’s see what happens when you do it a second time. Only with shitloads of stuff strapped to your back and actual things to accomplish once you get to the top.
As I mentioned, one of the best places to find recent material from Taranaki’s last eruptions is way up at the top. Looking at Taranaki’s most recent lava flows can help us in lots of ways. We can compare it to material we find lower on the volcano. We can look at fresher and more weathered material. We can look at different parts of the lava dome to see if the lava cooled at different rates in different places and try to learn what ways it affects the lava’s properties.
But the simplest thing we can try to do with those hot hot lava rocks (that are now cold) is try to figure out how old they are. If we decide that the lava dome at the top of Mt. Taranaki’s collapse was probably the last thing to happen there, then if we figure out how old those rocks are, we can probably tell when the volcano last erupted.
(The reason we don’t know this already is because the last eruption was before European settlement of the area. From this we know it must be older than at least the mid-1800s. Maori people were there at this time, for sure, but as far as I know there aren’t any datable written records or stories tied to an eruption.)
Our goal for this trip was to collect samples that I could try to date using paleomagnetic methods in the lab in Wellington. On my trips lower down you may remember me collecting rock samples that I would drill holes in in the lab later. But this time we decided to go full on and collect our cores in the field in order to be as accurate as possible.
This was a bigger job, though, so it required a bigger team. A both of my Auckland-based supervisors, Shane and Mike, and a couple fellow students from Auckland, Edgar and Jie, came with me, along with my friend Elisa, our Wellington-based paleomag expert.
For starters, the trip was longer than the first time. We’d be climbing two consecutive days, meaning we had to carry a whole bunch of food in addition to our gear (and possibly some lovely boxes of wine–we do our geology in style!). Oh, yeah…the gear. Hammer, chisel, chainsaw-sized drill and all its accessories, and more. Heck of a lot more than I had on my fun first climb.
We made our camp at the same awesome Tahurangi Lodge that I stayed at last time. It was definitely nice to have a little comfort at the end of the day.
From there, our first job was to hike to the top. Now, doing paleomag drilling is simple enough when your outcrops are by the roadside. Stop somewhere and fill up your water tanks, pull up on the side of the road, do your thing, go home. If you run out of water, just fill up again and get back to work.
In our case, however, we had to get all that same stuff to the top of the of the volcano to get to our sample sites, and there was nowhere to get more water once we were up there (we gave some thought to melting snow, but couldn’t come up with an efficient enough solution). That meant splitting up about 45 liters of water, a couple liters of fuel, and all the drill stuff between everyone for the trip up. It was probably the most difficult fieldwork I’ve ever done — steep enough as is, but even harder when weighed down by a super full pack.
But we did make it! Hooray! Once we were up there, we moseyed around to the western side of the summit to see the collapsed crater. That’s where the volcano’s most recent lava dome grew, then collapsed, leaving a giant horseshoe-shaped amphitheater behind. This was probably sometime in the 1800s, but we don’t yet know for sure.
In order to compare different parts of the dome and learn as much as we can about Taranaki’s most recent activity, we needed samples from lots of different parts of the dome, which meant climbing all around the collapse amphitheater and around the snow fields to pick out a few different sites to core.
Once we’d taken a good look, we picked some sample locations on different parts spread around the area and got to work drilling our cores. Drilling and orienting is a team effort. For the most efficient work, it takes two to drill–one to do the actual drilling and one to man the pump bottle to keep water running through the drill so it operates well. Then it takes another one or two to take accurate measurements and write careful on the cores and collect them to take home — that way the drillers can already move on to the next site. ***drilling note at end***
In order to learn more about the formation of the lava dome, we made sure to take samples from both the outside carapace of the dome that had cooled and remained in place as well as the fresh material that is newly exposed where the side of the dome collapsed. That way we can try to look for differences between the two types: Did one cool faster? Do they contain the same minerals? Are the mineral crystals different sizes? Did they record the same paleomagnetic field?
As you saw in the picture above, we usually drill about 8-12 small holes per site, and on the first day we were able to do five sites. Not bad for a day’s work! And we felt pretty good about having carried all that water since we used almost all of it. Imagine how upset we would have been if we’d worked so hard to get up there and then quit early because we ran out!
On the way down we were treated to some pretty awesome views or the surrounding area. The perfect circle of the edge of the park still impresses me. Combined with the shadow Taranaki casts in the evenings, it’s a pretty unusual sight.
Back at the lodge were were able to have some delicious soup packets, tea, dinner, and wine, and rest up for day two.
So did I complain about the first day being the hardest fieldwork I’d ever done? I was being a wuss. Day two was the hardest fieldwork I’ve ever done. Carrying all the same stuff up the volcano a second straight day was seriously hard work and at times frustrating (especially when constantly sliding backwards trying to climb the scree field) — early on I was genuinely concerned I might not make it! But after some tough times in the early going, we actually all made it to the top faster than we did on the first day.
The weather wasn’t nearly as good the second day, it was quite a bit chillier, and visibility was pretty low. Luckily my supervisor had a good idea where we were going. We did another four sites — some were more parts of the lava dome, but we also sampled The Turtle, an interesting feature a little ways down from the top that is very visible when looking at Mt. Taranaki from the west. Despite some tough conditions and a bit of slipping and sliding, we stayed focused, worked hard, and got everything we needed so that all our sarcastic comments about having to come up a third straight day could just remain jokes.
After staying another night in the lodge, we were able to head home with all the samples we needed to do a good investigation, and also comfortable in the knowledge that if we ever need to come back and get more samples, we’ll know exactly what to do. I’ve already gotten my teeth into testing the samples from this trip in the paleomagnetism lab down in Wellington, and though we don’t have any conclusive results yet, we’re well on our way to learning a lot more about the lonely volcano.
***Note on drilling: Mt. Taranaki is a beautiful and culturally important mountain. As such, we make our best effort to be as non-disruptive and non-destructive as possible when doing fieldwork. But sometimes the only way to do the science is to take the samples, as in this case. Before we even planned the drilling, we consulted with the NZ Department of Conservation and local iwi to get all proper permissions for the work and to make sure we did it in a way where all parties involved could be happy. When actually on the mountain, we always made an effort to drill our cores in places far off the beaten path where they won’t bother anyone, and often in areas where weathering and further collapse will likely remove them altogether over time.***