Landforms of ice and debris transport marginal to the glacierized zone of the Southern Alps, New Zealand, have been classified into debris-covered glaciers, cirque floor lobes, and talus-derived rock glaciers. Mapping of fossil and active landforms reveals a zonation within the Ben Ohau Range in terms of both landform type and activity status. The dominant distinction of active forms is between relatively ice-rich forms (glacial origins) in the humid north and relatively debris-rich forms (periglacial origins) in the more arid south. A secondary altitudinal zonation distinguishes currently or recently active forms at high elevations from fossil forms at lower elevations. Estimates of mean annual precipitation and of the altitude of the –2°C mean annual isotherm indicate that glaciers and active talus rock glaciers are located within the climatic boundaries identified for the European Alps. However, many fossil forms also occur within these boundaries where cirques are broader and shallower. These findings confirm earlier suggestions that permafrost occurs in the Southern Alps, but is restricted to a narrow zone above 2000 m. The study demonstrates the importance of relative ice-to-debris fluxes in determining the developmental pathways of landform genesis over both space and time.

The relationship between climate and rock glacier distribution in the Ben Ohau Range, New Zealand

The morphology and surface ages of talus-derived rock glaciers are investigated to establish the timing of rock glacier formation in the central Southern Alps. Samples of rock weathering rinds show that all rock glaciers studied were formed during the Neoglacial period, but differences exist between sites in the number of new rock glacier lobes formed by Holocene climatic fluctuations. A qualitative conceptual model is proposed to explain rock glacier formation in terms of two thresholds. An external threshold relates to the presence of a cool climate capable of allowing internal ice to form within talus slopes. An internal threshold relates to the presence of sufficiently thick talus at a site to generate a shear stress capable of overcoming internal friction within the talus/ice mass. The model produces a non-steady-state response to explain why unmodified talus, single-lobed and double-lobed rock glaciers developed at adjacent sites under the same climatic regime. Individual landforms have different sensitivities to formation, which depend partly on the previous history of talus accumulation and rock glacier activity at a site. The model demonstrates how successive cool climate periods may be fully represented by rock glacier lobes at sensitive sites but under-represented at insensitive sites. Sensitivity (and therefore climatic representativeness) is favoured by high rates of debris supply. By implication, the timing of formation of rock glacier lobes in regions of prolonged cool climate and low debris production is less likely to correspond to the timing of climatic cooling and more likely to follow the ‘rules’ of deterministic chaos.

On the sensitivity of Holocene talus‐derived rock glaciers to climate change in the Ben Ohau Range, New Zealand

This paper presents empirical data on non-sorted patterned ground in the high Drakensberg. Some morphological and sedimentary characteristics for thufur and nonsorted steps are provided. The study also examines process data on ground heave activity at a thufur site. Contemporary cryogenic activity at the non-sorted steps is indicative that the patterns are at least seasonally active. Soil heave measurements at the Mashai Valley thufur site support the contention that some thufur are active in the high Drakensberg.

Non-sorted Patterned Ground in the High Drakensberg, Southern Africa: some new data

The heavily glaciated Mount Cook Region of New Zealand has experienced several recent large rock instabilities,
but permafrost conditions related to these events remain unknown. This work presents the first systematic approach
for investigating the distribution of mountain permafrost in New Zealand. At this level of the investigation, a firstorder estimate is based upon the adaptation of established topo-climatic relationships from the European Alps. In the southeast of the study region, the permafrost estimate gives a reasonable correspondence with mapped rock glacier distribution but the maximum elevation of vegetation growth is situated 200 m beneath the lower limit of estimated permafrost. Extreme climate gradients exist and towards the humid northwest, where rock glaciers are absent and vegetation patterns give an unclear climate signal, large uncertainties remain. Data currently being recorded from a network of rock wall temperature measurements will help remove this uncertainty, and will allow distribution modeling that better accounts for the topographic complexities of this steep alpine region.

https://www.zora.uzh.ch/id/eprint/5447/2/Allen_Owens_First_Estimate_2008V.pdf

A first estimate of mountain permafrost distribution in the Mount Cook region of New Zealand’s southern alps

This paper outlines recent advances in our understanding of periglacial processes and landforms in mountain areas, as reported in the literature over the last 8 years. Landforms investigated include rockwalls, screes, avalanche paths, bedded slope deposits and patterned ground phenomena. Processes subject to quantification include cliff recession, rock displacements on slopes, rock thermal and moisture regimes, frost creep, mass wasting and solution. Laboratory experimentation and modelling studies have also been undertaken.



Le present article souligne les progres recents de la connaissance des processus periglaciaires et des formes de terrain dans les regions de montagne ainsi qu'ils apparaissent dans les publications des 8 dernieres annees. Les formes de terrain etudiees comprennent les abrupts rocheux, les eboulis, les couloirs d'avalanche, les depǒts de pente stratifies et les sols structuraux. Les processus dont on mesure la vitesse sont le recul des abrupts, les mouvements des roches sur les pentes, les regimes thermiques et d'humidite des roches, le creep dǔ au gel, les mouvements de masse et l'erosion par mise en solution. Des experiences en laboratoire et des modelisations ont aussi ete entreprises.

Present‐day periglacial processes and landforms in mountain areas

The presence of periglacial phenomena and activity in New Zealand is controlled primarily by altitude, especially as modified by topography and lithology. Thus, the alpine-type mountains that form the backbone of the South Island (Southern Alps) show little in the way of patterned ground, while the block mountains of Otago and less sharply peaked mountains in Canterbury and Marlborough display these features on varying scales. Some forms are considered to be fossil, while others are at present active. This paper reviews the distribution and character of periglacial phenomena in New Zealand, as well as the broad factors controlling their origin and development.



L'occurrence des phenomenes et de l'activite periglaciaire en Nouvelle Zelande est reglee par l'altitude, surtout modifiee par al topographie et la lithologie. Ainsi les montagnes de type alpin formant l'epine de l'ǐle du Sud (Alpes du Sud) ne montrent pas beaucoup de sols a figures geometriques, alors qu'on les trouve a plusieurs echelles dans les montagnes d'Otago et celles moins pointues de Canterbury et Marlborough. On pense que quelques unes de ces formes seraient fossiles, mais que d'autres seraient actives actuellement. Cette communication passe en revue la repartition et le caractere des phenomenes periglaciaires en Nouvelle Zelande ainsi que les facteurs generaux qui contrǒlent leurs origines et leur developpement.

L. W. Price

Papers

Periglacial phenomena in New Zealand