The morning of day three we left the quaint city of Christchurch and started our journey to the Wild West coast of New Zealand. The morning started off rather foggy but just as we reached Sheffield, the clouds lifted and glorious meat pies sat awaiting us. We crammed back into the van with happy hearts and full stomachs as we continued our journey to the first geologic stop of the day. After passing what seemed like thousands of sheep and oreo cows, we pulled into the parking lot of Castle Hill. The magnificent boulders seemed to compose a mighty fortress on the grassy hillside and we gazed in awe at this shear geologic masterpiece. After exploring the crevices of castle hill and taking a closer look at the sediments through our hand lenses, we concluded that these rocks were made of limestone as many of them contained pieces of coral or shell material and had been eroded through processes of dissolution since the time they were lithified and uplifted. We also learned to use the word “colorless” as opposed to “clear” because (in the words of Guil) it is “not CLEAR what you are trying to say”. Castle Hill was originally a beach where sea life flourished and small-grain sized particles were able to be deposited, creating the limestone we find ourselves standing on today. We also were able to piece together why the beds we were observing did not reside in their initial horizontal orientation. This was due to tectonic activity in the region and the uplift and erosion that had occurred following those events. But the excitement had not concluded yet . After we had uncovered the origin of Castle Hill, we hunkered down on one of the boulders and were briefed in the art of finding strike and dip. We grabbed our compasses and followed a set of steps using the right hand rule, giving the rock a low-five, and even singing the little tea pot song! Although many of us left that lesson flustered and still trying to distinguish our right hand from left, we would soon realize how valuable strike and dip measurements could be in the following days.
Our next major stop of the day was at the braided channels of the Waimakireri, New Zealand’s largest river system and one of the first rivers in the world to have rights! We gazed in awe at the bright blue water and the magnitude of this sediment system. We learned that the mountain system surrounding the river allowed for water to drain quickly, creating a high energy environment for sediment to be transported. This constant movement of sediment allows for the river to shift and create new channels.
As we continued to traverse the South Island we stopped a third time to enjoy the stunning scenery in Arthur’s Pass or New Zealand’s Continental Divide, where the rivers shift and flow towards the West Coast. We even got the chance to see a Kia, a parrot native to New Zealand.
Our final stop of the day was at the tectonic boundary between the Pacific and Australian plate. We were puzzled at first by the sudden shift from mountains to plains but quickly discovered that this was the transform Alpine Fault. Although the boundary was not terribly impressive, we learned that this was because one plate was sub-ducting and the another was being uplifted but not eroded. This allowed for the dumping of sediment and the creation of some of the fastest moving mountains in the world.
As the sun went down we pulled into Westport and got settled at the University of Canterbury field station, exhausted after our adventure filled day. We hit the hay, ready to take on our first full day on the west coast.
We braved the wind and rain to put our compasses to use at 14 mile creek beach. At the first outcrop, we noticed that there were tilted layers and vertical fracturing. There were also crossbeds but no visible individual grains or porosity. With this information, we decided this outcrop was metamorphic, specifically a metasandstone. We were then given the task of finding the strike and dip for both the bedding and the fractures. We continued this for four more stops until the tide came in, which forced us to take a little detour. Later that evening, we drew the dip of the bedding and fracture for each stop on a piece of paper. From this, we discovered that the bedding constructed an antiform. This was formed from force that folded the layers, also causing fractures to form perpendicular to the stress. Due to the presence of crossbedding, we were also able to classify it as an anticline, meaning the youngest layers were on the outside.
After drying off and eating lunch, we drove to our next stop near Fox River beach. This outcrop was about 15 or 20 meters of poorly sorted, angular, layered rocks. The outcrop was formed from a high energy environment close to the source, likely from multiple mass wasting events. We concluded that this rock was a sedimentary rock, but we were stumped by the tilted layers that we thought should have been horizontal. This orientation was created from a nearby fault’s discrete motion. Each time the fault moved, wedges of sediment were created so that the dip angle increased with depth. This could inform us of the faults past activity.
Our next major stop of the day was at the braided channels of the Waimakireri, New Zealand’s largest river system and one of the first rivers in the world to have rights! We gazed in awe at the bright blue water and the magnitude of this sediment system. We learned that the mountain system surrounding the river allowed for water to drain quickly, creating a high energy environment for sediment to be transported. This constant movement of sediment allows for the river to shift and create new channels.
As we continued to traverse the South Island we stopped a third time to enjoy the stunning scenery in Arthur’s Pass or New Zealand’s Continental Divide, where the rivers shift and flow towards the West Coast. We even got the chance to see a Kia, a parrot native to New Zealand.
Our final stop of the day was at the tectonic boundary between the Pacific and Australian plate. We were puzzled at first by the sudden shift from mountains to plains but quickly discovered that this was the transform Alpine Fault. Although the boundary was not terribly impressive, we learned that this was because one plate was sub-ducting and the another was being uplifted but not eroded. This allowed for the dumping of sediment and the creation of some of the fastest moving mountains in the world.
As the sun went down we pulled into Westport and got settled at the University of Canterbury field station, exhausted after our adventure filled day. We hit the hay, ready to take on our first full day on the west coast.
We braved the wind and rain to put our compasses to use at 14 mile creek beach. At the first outcrop, we noticed that there were tilted layers and vertical fracturing. There were also crossbeds but no visible individual grains or porosity. With this information, we decided this outcrop was metamorphic, specifically a metasandstone. We were then given the task of finding the strike and dip for both the bedding and the fractures. We continued this for four more stops until the tide came in, which forced us to take a little detour. Later that evening, we drew the dip of the bedding and fracture for each stop on a piece of paper. From this, we discovered that the bedding constructed an antiform. This was formed from force that folded the layers, also causing fractures to form perpendicular to the stress. Due to the presence of crossbedding, we were also able to classify it as an anticline, meaning the youngest layers were on the outside.
After drying off and eating lunch, we drove to our next stop near Fox River beach. This outcrop was about 15 or 20 meters of poorly sorted, angular, layered rocks. The outcrop was formed from a high energy environment close to the source, likely from multiple mass wasting events. We concluded that this rock was a sedimentary rock, but we were stumped by the tilted layers that we thought should have been horizontal. This orientation was created from a nearby fault’s discrete motion. Each time the fault moved, wedges of sediment were created so that the dip angle increased with depth. This could inform us of the faults past activity.
We ended the day full of fish and chips and excited to experience more of the west coast!
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