Pumped on Pumice!

Now that I’m not completely jet-lagged, I can give all of you a proper blog post… or at least try. So here it goes!

Today was our first real day of field work. It started off like any normal day of field work usually does: early and getting the coffee going. Fortunately, with it being summer down in New Zealand there is plenty of daylight, so when our alarm went off at 6:30 getting out of bed wasn’t really a challenge. Could I have slept 4 more hours and fully recovered? Sure, but my excitement to actually go look at some volcanic rocks won out and getting out from under the sheets wasn’t really all that bad. Everyone else, based on their demeanor, also felt the same and we all gathered around the central cabin to eat breakfast and make our lunches. Today’s menu consisted of sandwiches, granola bars, and fruit. When doing field geology it’s best to keep your food simple and portable.

As 8:00 came around we were off to our first stop on the western edge of Ohope beach where we would discuss a little bit of the background of the northern TVZ, what makes it so unique in the world of volcanism, some basic goals of our research proposal, and to look at some tephra (air fall) deposits from some of the more recent eruptions. It was a bit of the climb to get out to the overlook where we would discuss the aforementioned topics, but it was hardly anything too rigorous. Surfers were scattered throughout the beach getting ready to catch some waves and the sun was already shining down in full force warranting a thorough coat of sunscreen. Apparently, the sun down here in New Zealand can be quite intense, therefore I’m not taking any chances. We spent a couple hours here and then went back down into town for a coffee break. As I’m sure you will soon realize, these coffee breaks are a regular thing and fuel most of our research.

After everyone got refueled on caffeine, it was time to go sample some eruption deposits, specifically the Matahina (320,000 years old) and the Rotoiti (45-50,000 years old). FINALLY. Time to do what we all came here to do. Getting to these outcrops wasn’t anything particularly rigorous, as they make up the majority of the roadside cliffs here along the Bay of Plenty, but the traffic and lack of road shoulder almost turned this into an extreme sport. Logging trucks will win a head on battle with a geologist 10 times out of 10. Nevertheless, we went to work on these hundred meter cliffs of ignimbrite and started filling our sample bags with pumice chunks that were scattered throughout the rock unit. The reason we sample the pumice and not the whole rock is, that, the pumice offers a definitive snap shot of what the magma composition was like within the magma conduit/reservoir immediately before eruption. This is because pumice is rapidly cooled magma. It cools so fast that it traps pockets of air inside of it, hence it’s vesiculated nature and ability to float. These rapidly cooled chunks of magma get trapped in pyroclastic flows during eruption events and when the flow completely cools give us the deposit we see today. One cannot be certain that the surrounding groundmass of rock is directly related to the magma composition, so we leave this on the outcrop and only take the pumice. Think of it as very crude scientific sculpting.

We stopped at 3 outcrops in total and collected 10, gallon sized bags of pumice. The pumice here is relatively crystal poor, so when doing intra-grain crystal studies we need to collect a lot of it in order to increase our chances of finding as many crystals as possible to do geochemistry on. As analytical techniques evolve to collect more accurate data in even less time, statistically valid data is now a very important thing to consider when doing geochemistry!

Post field work we stopped to get some fresh New Zealand ice cream at Blueberry Corner, and as someone who loves ice cream, I was pretty much in heaven. Made with fresh blueberries, strawberries, and raspberries, this ice cream was absolutely magnificent. 10/10 would recommend when you’re on the North Island. It was then time to go grocery shopping and stock up on food for the next few days while we’re up by the coast. Even though we like to think we can power our whole research project by coffee, we still need calories and actual food to get through the day. Dinner tonight consisted of burgers, brats, heaps of grilled vegetables, and some good kiwi beer or wine.

Time to go over our notes, samples, and plans for tomorrow. Things are off to a great start for the Tephra Team.

More soon!

Cheers,

Lubbs

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2 Replies to “Pumped on Pumice!”

    1. We have to fill out some special paper work and then will mail them. Since they are not historic artifacts or contain any seeds/invasive species it really isn’t all that problematic. We can just mail them. If, however, we were trying to bring back aforementioned items it would be a little more challenging.

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