129-35 Cirques in the Southern Alps of New Zealand: Identification and Measurement of Glacial Features

Abstract:

Cirques are armchair-shaped erosional features that form in high alpine settings by cirque-type glaciers abrading the base-rock and carrying away material. These features are useful for understanding the extent of previously glaciated environments. Cirques are characterized by a steep headwall, an overdeepened bowl-shaped basin that often has a tarn, and a lip that marks the bottom extent of the cirque. There is minimal data on cirques in New Zealand, especially in the Southern Alps, and this study seeks to fill this gap. Here we create a dataset identifying 255 cirques across ten sections in the Southern Alps region of New Zealand and complete six morphometric measurements on each cirque. These measurements, conducted using GIS, included aspect, minimum elevation, depth, width, length, and area. Comparisons were drawn between cirques located closer to the Main Divide – the principal mountain ridge of the Southern Alps – and cirques located further from the Main Divide. Cirques closer to the Main Divide form at higher elevations, show a wide array of aspects, and are seemingly less developed than cirques further away from the Main Divide. We observed that cirques further away from the Main Divide exhibited strong directionality and were often larger in size. We anticipate that our data could be of use to future researchers studying cirques in the Southern Alps. Our observed trends can be used to interpret geological and climatic conditions under which cirques formed, and to understand the post-glacial processes which may have altered the morphology into present-day cirques. Additionally, our data can provide a basis for further research of cirque morphology, tectonic uplift, climate patterns, or further comparison of the Southern Alps area cirques with those from other regions worldwide.

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