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Mount Jerai from Pedology and Soil taxonomy Perspectives

posted Sep 6, 2021, 8:04 AM by jeffery jim
Based on Generalized Soil Map of Peninsular Malaysia (1970), Mount Jerai consists of Red-Yellow Podzolic Soils with Lithosols acids to intermediate igneous rocks (13) at the steepland and surrounded by laterites on residual materials from argillaceous sediments and metamorphic rocks (12) rolling and low hill area. In addition to that, Soil Map of Malaya (1962) highlights the center and extensive part of the mountain is Lithosols and shallow Latosols. Based on FAO classification of major soil grouping, Latosols is also known as Ferrasols which is dominated by low activity clays which is mainly Kaolinite and sesquioxides. The parent materials are Mafic or basic rock and Felsic or acidic rock the only issue is poor drainage due to 2:1 clays and Kaolinite where the stability of the soil very much depending on the clay type of bonding involving positively charged iron oxides and the negatively charged Kaolinite (unlike sand and aggregate which are in equilibrium due to angle of friction). Unlike its famous counterpart soils in Sabah, the Acrisols which have high potential of soil erosion due to its ability to retain water saturation, Ferrasols are usually stable until the weatherable minerals start to diminish and cation retention begins to wane instead of formation of non-permeable crust.

This kind of soil is chemically poor soils where the bonding is depending on the highly changed variability where the negative charged soil is independent of the soil pH value where as the main clay mineral of Kaolinite have very low permanent charge. Sesquioxide is the organic binding agent which actually helps with the aggregation and aggregate stability of soil and will wane off.

Soil Taxonomy studies from the Reconnaissance Soil Map of Peninsular Malaysia (1968) shows that the affected area consists of Keranji soil (2) and cordoned by Melaka-Tavy-Gajah Mati soil (25) at the north and Rengam-Jerangau soil (32) and partially Telemong-Akob-Tanah Lanar Tempatan (11) at the south. The study will emphasize on soil 25 which is a combination of Melaka and Tavy soils based on DID’s ESC Design Guideline (2010). Both Melaka and Tavy soils are clay soils under HSG Group D with soil erodibility factor between 0.049 and 0.052 n the top three strata until the depth of 1.5m. Mount Jerai is situated with mediocre rainfall erosivity in comparison to the east coast of the Peninsular and the Federal Territory of Kuala Lumpur, which does not trigger extraordinary issues when it comes to precipitation and the affect on aggregate instability periodically.

Nevertheless, from the rainfall data acquired, the issue would be the rainfall depth contributes to the tragedy. It has been raining with 50mm depth almost constantly since 11th August, Like most landslide, it takes few days of rain to trigger erosion induced landslide with perfect wetting and drying cycles where 20mm rainfall is a critical daily amount of rainfall that is liable to trigger erosion according to Roslan and Tew (1997). During the event, the rainfall precipitation reached 283mm and coupled with slope steepness as well as slope length, it is the formula that leads to catastrophe. The amplitude of slope length can be very devastating especially in this case where it could reach a thousand folds for slope length value for the empirical calculation. In addition to that are argillaceous soil easy detachment and high soil erodability factor.

After conducting an hour of desktop study and reconnaissance, it is clear that claims that this event is due solely to logging is not true but I reckon that compromising with nature is probably the main cause to such event. One of the many things that authorities should probe would be the changes of chemical composition of the soil until substratum that may actually trigger erosion when aggregate stabilization and waning of minerals no longer helps clayey soil to be in equilibrium as it has always been. It is not understood how minerals at the surrounding area mainly at the steep areas depleted but there is possibility that reactions from wash-off or wastewater from quarry or the use of chemical or enzymes for road stabilization and embankment construction which may actually seeped through and contaminate the whole area as Ferrasols have efficient water dispersion capacity within the subsoil or subsurface. Due to lack of information on the granite with porphyritic aggregates, no information and summary can be made based on the existing matrix to see its maturity and stability level in relation to reactivity to elements mentioned earlier to Alumium ions as well as Ferum Oxides.

The concern would probably the possible use like sulfuric acid for rock extracting, or purely due to negligence the fact that the quarry forgot they are mining Lithosol acid may lead to aluminum ions dissolved in the soil or simply acid mine/rock drainage which is not tackled properly. It is also hard to distinguish acid drainage since its color is similar like typical laterites.

For more of geological original post, kindly refer to the article by P.Geol

May be an image of map and text that says "E 100.1° E 100.3° E 100.5° Bunting E 100.7° 5.8° P. Bidan N Study Area Sayak N5.8° sgeani N5.6° SILURIAN ORDOVICIAN Legend: Schist, phyllite, slate and limestone. Minor intercalations of volcanics. PERMIAN Clay and Silt (marine) Phyllite slate and shale with subordinate sandstone Schist. Prominent development -N5.6° WAAR avel-undifferentiated Clay, silt, sand and (continental) CAMBRIAN N5.4°- Succession Volcanics rhyolitic to andesitic composition, widespread. Sandstone/ /metasendstone with subordinate siltstone, Shale and minor conglomerate IGNEOUS ROCK Sandstone metasendstone Acid intrusive (undiffentiated). highway E 100.1° Road E 100.3° River N5.4° E 100.5° E 100.7°"