After exploring the realm of effusive volcanoes at Ruapehu, we ventured out into the unknown world of explosive volcanism. We started our day with a hot mystery to solve: fall or flow?
We were taken to 2 outcrops that were textbook perfect examples of each volcanic feature and set upon characterizing them. Two very different pyroclastic depositions were evident--one with big white pumicey clasts with no beds and one tall hill with clear layering and varied grain size-- but there was a steamy debate as to which was flow and which was fall. Left without the guidance of Guil, Lydia, and Brad, the gang was left to our own devices to figure out which was which.
Leaving our mystery up in the air, we headed to our third stop - a hill. Bushwhacking our way up through towering grasses, we traversed our way to a place that looked suspiciously like the second outcrop. After another heated debate amongst the students, we eventually learned that this was, in fact, a combo of proximal explosive material, much to some of our groups' disappointment. Interestingly, this deposit and a second one that Brad had climbed pointed towards a valley as their origin - meaning it used to be the center of a volcano! Whoa!!!
Our final stop of the day was up up and a ways away. We climbed a hill that had what felt like a 90-degree angle, clambering up the steep slope and found a muddy perch at the top to observe a second cone. We talked about which center came first as the clouds threatened us with their speedy approach. Soon we were (not so) comfortably in the cloud mist discussing how the valley persisted through time and through many volcanic events. Valleys winning the battle against volcanoes was a big win for the valley girls! Then we made our daring descent down the slippery slope. Some of us trudged through the brush clinging to bushes while others skated down on dirt alone. Brad skateboarded down with ease and glee while some of us others slipped once or twice (or ten times).
Once warm and cozy back at the Skotel, we put our thinking caps on to solve the mystery from earlier. 45 minutes later (we couldn’t be late to dinner again) we handed in our frantic sketches and theories on which pyroclastic deposit was which. Our consensus: the first outcrop was a flow and the second was a fall! This is because of the “in-filling” topography of the flow and the sorted layers of angular pumice in the fall.
Our final stop of the day was up up and a ways away. We climbed a hill that had what felt like a 90-degree angle, clambering up the steep slope and found a muddy perch at the top to observe a second cone. We talked about which center came first as the clouds threatened us with their speedy approach. Soon we were (not so) comfortably in the cloud mist discussing how the valley persisted through time and through many volcanic events. Valleys winning the battle against volcanoes was a big win for the valley girls! Then we made our daring descent down the slippery slope. Some of us trudged through the brush clinging to bushes while others skated down on dirt alone. Brad skateboarded down with ease and glee while some of us others slipped once or twice (or ten times).
Once warm and cozy back at the Skotel, we put our thinking caps on to solve the mystery from earlier. 45 minutes later (we couldn’t be late to dinner again) we handed in our frantic sketches and theories on which pyroclastic deposit was which. Our consensus: the first outcrop was a flow and the second was a fall! This is because of the “in-filling” topography of the flow and the sorted layers of angular pumice in the fall.
Margaret & Emma
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