Fieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldworkfieldwork! Woot woot!
If you remember back when I started this thing, I promised a healthy dose of science and geology to go with the pretty pictures. Unfortunately, except for one trip report in June, I haven’t been able to follow through on that promise particularly well. But that ends today! Inform the men and women, it’s geologizin’ time! Prepare to be scienced! If you have a weak constitution or an un-curious mind, please leave now, because wimmity-wam-wam-wazzle hallelujah it is fieldwork season, and all is well with world!
Assembling the G-Team (G is for geology)
Finally presented with several consecutive days of good weather forecast, I planned a three-day field trip and asked along lots of geology and non-geology friends to be field assistants. Many jumped at the chance to do a little tramping and I ended up with a crack international team of doctors (the geology kind), engineers, PhD students, and more! Overqualified for a preliminary light field trip? Probably. Overqualified for having fun? Not a chance!
The goal for this trip was to scope out the area that where I’ll be doing most of my field work, get an eye for telling the difference between different types of volcanic deposits, and pick some good spots to come back and sample another time. After driving down, we spent the rest of the first day looking for some huge debris avalanche deposits along the coast (a side project). It took a bunch of tries driving up and down some little roads, but eventually we found what we were looking for.
For both nights of the trip, we camped in a small clearing right at the edge of the national park. As long as the weather is good, that’s definitely going to be a great cost-saving measure going forward. Camping right next to cars is easy since you don’t have to carry stuff far before you set it up, and cooking and sharing an evening with friends outside only makes the trip even more enjoyable.
Our campsite. Pretty nice view, huh? Also, can you guess where the farmland ends and Egmont National Park starts? Hint: it’s as obvious as it looks.
The Real Work Begins
The goal of the second day was to go into the park and find stratigraphic sections of the deposits I’m going to be working with in the future so I could get practice looking at them, describing them, and deciding what type of deposit they are. A stratigraphic section is basically a place where you can see lots of different layers of rocks or volcanic deposits all stacked on top of each other in one place. It’s important to study these because it’s the easiest place to learn what all the different layers look like, since in many places only some of the units will be present and it isn’t nearly as easy to tell them apart.
Once we found Maero Stream, we hiked up and down a bit looking for the “type section”, which is basically the very best stratigraphic section anyone has found of a particular sequence of deposits, and therefore the best place to learn about them.
What I actually mean when I say “I look at rocks for a living”
Looking at a section is a multi-step process that starts with seeing what you can learn about the outcrop from a distance. How many different layers are there? How thick is each one? What can you tell about each layer on a large scale? Basically, ask as many questions as I can think of and see how many I can answer.
That’s followed by going up close and looking at each layer individually. How big are the biggest rocks in a layer? How small are the smallest ones? What type of rocks are they? Do the rocks get bigger or smaller as you look up or down? Are similar size rocks grouped together or is it totally random? Answering these questions may help me figure out other things about the deposit, like where it came from, how hot it was, and more.
After looking at the type section, we went on to look for some “reference sections,” which are basically more good spots to see a particular formation, just not quite the best ones. That involved crossing some more streams and led, finally, to some awesome views of the big guy himself.
Getting to the reference section involved hiking up the Stony River (also called the Hangatahua River), the largest, wettest river in the area by a solid margin. Even on this dry day it was pretty big, and will probably be pretty hard to cross except in the driest of times, which meant I had to look at a lot of stuff from a distance.
And that was pretty much it for the day other than the hike out. Part of doing this kind of fieldwork involves being patient and being happy with what you got done for the day. While there will be some days where I take tons of samples or look at a bunch of sites really close together, there will be others like this one where you walk pretty far just to see one particular site and have to be satisfied with that as a productive day.
The goal of the next day was to check out a few spots I had marked off outside the park to look at a different unit. While the Maero Fm. we were looking at the previous day is only up to 800 years old and from the volcano’s most recent active period, this day we’d be looking at the Warea Formation, deposits from activity closer to 10,000 years ago. The idea is to look for comparisons between the two units from different time periods but in the same area–how were the conditions similar or different the last time the volcano erupted in the same location?
So we jumped in the car and gave chase. Alright, so we weren’t driving all that fast. And the things were were chasing were inanimate objects that have been there for a few thousand years and probably aren’t going anywhere. Still, it’s more fun to think of myself as a rock bounty hunter tracking down my quarry (bad geology pun alert!)?
Whereas the deposits we looked at in the park mostly showed characteristics of a hot pyroclastic flow, the things we looked at outside the park looked different, more likely being a cold, wet lahar. Except, there was more to see…
There was one unit that had some characteristics of both hot and cold deposits! Tricky, indeed. That’s where my paleomagnetic methods should come in handy. Later on, when we come back and sample, I should be able to do pmag lab work that will give me a better idea of what type of deposit we were looking at.
With the hard work mostly over, we decided to relax and eat our lunch at the beach. And by beach I mean more rocks. Also, we made a friend!
And there’s another field trip in the books. Can’t wait to get back with some sampling gear to start the real work!
A New Zeal and an Old Volcano 