Amanda Bucci's Geopost cards

This is the site of the Tangiwai Railway Disaster located near National Park on the North Island of New Zealand. In 1953 on Christmas Eve, Mount Rupaheu’s crater lake’s natural volcanic ash dam collapsed, causing a mudflow, or a lahar, to plow through everything in its way—including the Whangaehu River, one of the main drainage paths of the mountain. An uninformed train carrying 285 people went over this bridge just minutes after the lahar came through, and as a result, the bridge collapsed into the river. Out of the 285 people on board, 151 died. This is the worst natural disaster to occur in New Zealand’s history. The high viscosity and high density of the lahar has enough momentum to move large boulders, like the ones pictured here. Since this tragic Christmas Eve, the railway company has installed signaling systems to alert conductors about broken rails, and Mt. Rupaheu’s crater lake is being highly monitored for any more dam failures that could cause another deadly lahar.

Pictured here is a moraine next to the Mueller Glacier where we conducted our geology field work on the South Island of New Zealand. In the background is Mount Cook, the highest mountain in New Zealand, and in the right hand corner is a picture of a lichen, which was the focus of our field work. Lichens are the premier pioneering species to grow on a rock after it has been deposited. By measuring the long axis of a lichen, and corresponding the measurement to years on a graph, scientists are able to tell the approximate age of the moraine that the boulder and lichen lies on. When a glacier retreats or advances, it leaves behind large boulder deposits and glacial till that forms a moraine. By dating the moraines, we can tell when the last little ice age occurred in that area. There is usually a 10-20 year lag time from when the glacier deposits the boulder and when the lichens begin to colonize. This means lichenometry data is quite accurate, and simple to obtain. The green part of the lichen is the algae, and the black part is the fungus. The algae fix atmospheric carbon dioxide that the fungi feed off. This symbiotic relationship provides scientists with important data to use in enabling them to date a moraine to determine when the last little ice age was during the late Holocene period.