Sarah Holland- Postcard #1

Pictured here is a pumice terrace that marks the landscape next to Lake Taupo, on the North Island. Evidence of changes in water levels and other fluvial processes can be seen in the area’s many terraces which notch the topography. The pumice exhibited in the terraces was ejected over the landscape during an enormous explosion, possibly the Taupo explosion of 186 AD. The terraces have deposition layers of poorly-sorted and well-sorted material. The layers of well-sorted, finer sediment are volcanic ash. The ash can be deposited and redistributed for many years after an eruption and may also show evidence of stream or lake activity. For example, finer grained sediments such as volcanic ash are usually only deposited in low-intensity stream or wave environments unless they are of greater density than the larger substrate. In this case, since pumice is quite buoyant, the volcanic ash may have been deposited more easily. The poorly-sorted layers, where the pumice stones can be found, is evidence of not only an eruption, but also fluvial activity. The stones of pumice have been rounded, and in some areas, shingled. Both features are characteristic of the influence of streams on the landscape. For if they had been merely ejected and deposited, one would expect a more angular substrate. The youngest layer is eolian dust, or loess adding wind as another factor in the formation of this landscape. In summary, the pumice terraces have undergone processes of wind, water and time to appear as they do today.