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Wednesday, March 17, 2010

NATURAL SCULPTURES: White apilite streaks intrude into the granite between Donkey Ears and the Ugly Lady.

By Alan Rogers

CLIMATIC change prompted by human activity on our planet, which is witnessed in the melting of alpine glaciers, the diminution of the Greenland ice cap and the Antarctic ice sheet is a common topic more recently named Global Warming. In fact it is as old as the earth, but has accelerated over the last two centuries through industrialisation.
It is evident from erosional and depositional features on Mt Kinabalu in Sabah that during the relatively recent Pleistocene times (only 1.4 million to 10,000 years ago) the mountain was crowned with an ice cap sitting like a skullcap on top of a head.
This ice cap fed fast flowing valley glaciers which followed pre-existing river valleys radiating outwards from the summit. These lobes of ice were squeezed outwards by the pressure of the overlying mass of the main body of ice thus cutting deep valleys.
Towards the end of the Pleistocene (Ice Ages) ice was confined to higher summit levels in small semicircular bowl-like depressions cutting cirques or corries into the surrounding granite. The ice cap was thought to be five square km in area.
WHAT A CLIMB: Polished granite surfaces through ice abrasion and human feet. Labuan Rata Resthouse is seen towards the bottom right.
Evidence of past glaciation may be observed at Paka Cave, where the lower limit of a valley glacier is marked by the glacial melt deposits of a terminal moraine — the result of the glacier bulldozing frost shattered and angular rock fragments before it.
Jagged peaks at Low’s Peak, Donkey Ears and St John’s Peak bear witness of frost shattering, suggesting that these summits extended above the level of the ice cap and are referred to as nunataks — a word derived from the Inuit language in Greenland.
The smoothness of the granite on the fixed rope area towards the summit and the scratches (striations) caused by the sand papering effect of the ground moraine embedded in the base of the advancing glaciers bear witness to ice movement. Interestingly these striations criss-cross each other suggesting changes in the direction of the ice flows at different times in the Pleistocene.

The notorious Low’s Gully — a frightening drop of 1,524 metres — is typical of a trough where several spill glaciers from the ice cap converged to increase the ice velocity and thus its erosive force to cut out such a deep chasm. There the ice exploited a huge fault in the granite thus creating the near vertical rock walls.
Koopmans and Strauffer (1966) noted that above 3,350 metres the summit areas consist of curved horns and spires hence the ‘toothy’ profile of the mountain. There is the possibility of unidentified glacial moraines on the lower slopes of the mountain towards Kundasang. Glaciologists have yet to accomplish a full analysis of this area.
When the glaciers finally melted here in Sabah, only 3,000 years ago, mud flows containing frost shattered boulders of granite and sandstone flowed down the mountain and covered the surrounding area with deep deposits of mud and rock debris. These can be observed in Kundasang where the beds are 140 metres deep and on the Pinosuk Plateau.
What evidence is there of recent weathering, since the Pleistocene, on Mt Kinabalu? Certainly at Low’s Peak there are scree accumulations of angular frost shattered rock fragments with evidence of ice in frozen pools below. Water enters the joints in the granite, freezes and expands prising the rock apart. Continuous freeze/ thaw action leads to the further development of these joints. Add to this chemical weathering processes, which decompose the feldspar and mica crystals in the granite to break down the rock into clays. This is exacerbated by the high annual rainfall on the mountain with 2,750 millimetres per annum at 1,524 metres and over 5,000 millimetres on the summit.

Mt Kilimanjaro, in Tanzania, is occupied on its summit by fast-shrinking glaciers and is a present day model, at 1,220 metres higher than Mt Kinabalu, for the activities that once existed some 3,000 years ago on our tropical mountain in Sabah.
Like Mt Kinabalu, Mt Kilimanjaro is regularly climbed by tourists and adventurers. Had there not been climatic change, the summits and toothy profile of Mt Kinabalu would not be there and thus tourism would be absent. The fact that humans are influencing climate change is undeniable but as seen on Mt Kinabalu there is climate changed without human intervention. The evidence may be seen by an observant and discerning eye for a mountain.
References: Kinabalu — Summit of Borneo (The Sabah Society Monograph, Kinabalu, 1978); Cpt 4 Geomorphology by Lynn C Myers; Cpt.5 Geology by Gerry Jacobson; Geology and Topography of Kinabalu National Park by DV Jenkins; Berita Palanchang Vol II, No.1, p8 1972; Glacial phenomena on Mt Kinabalu, Sabah by B N Koopmans and P H Strauffer (Borneo Reg Malaysia Geol Surv Bull 1 1967).

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