Known locally as Telaga Tujuh, the Seven Wells Waterfall is named after the seven natural pools that have been formed at different levels by water streaming down Langkawi's second highest mountain, Mount Mat Cincang. It is arguably the most picturesque and best waterfall on the island.
According to folklore, the waterfall is believed to have healing properties and used to be a favourite bathing place of seven beautiful, ethereal maidens who would bathe under the moonlight. A local prince once tried to capture the fairies but they vanished into thin air, never to return.
Type of Earthcache: Planar failure.
Telaga Tujuh, the Seven Wells Waterfall.
Telaga Tujuh (Seven Wells)
The Telaga Tujuh waterfall is formed along the Sungai Perangin (Paringin River). It is formed between the Cambrian sandstone of Machinchang Formation and Late Triassic granitic rocks (Sawar Granite). In addition of being one of the finest examples of transition between two distinct rock types, it is also characterised by one of the clearest examples of planar failure in the region.
Planar Failure
A planar failure of rock slope occurs when a mass of rock in a slope slides down along a relatively planar failure surface. The failure surfaces are usually structural discontinuities such as bedding planes, faults, joints or the interface between bedrock and an overlying layer of weathered rock, as well as its orientation with respect to the slope face are the essential factors to the failure of rock slope. The pre-existing weak planes or discontinuities with unfavourable orientation are usually the failure surfaces of an unstable rock slope. In soils it appears generally in the form of a circular arc.
Compared to other failure modes encountered in rock slopes, planar failure is relatively rare. Planar failure seldom occurs because the geometric conditions required to produce such failures do not often arise in real slopes. There are a number of conditions that must exist in a rock slope for planar failure to occur. First, the failure plane must be sub-parallel to the slope face. This means that it must strike within 20 degrees to the slope face. The failure plane must also daylight into the slope face: it must have a dip shallower than the dip of the slope face, and intersect the face above the toe of the slope. Planar failure also requires the presence of release surfaces (side relief planes) at the lateral boundaries of the sliding block, providing insignificant resistance to sliding.
The geometry of the slope having plane mode of failure is defined by; inclination of the slope, upper slope surface inclination, slope height, potential failure plane - dip amount and dip direction, tension crack or upper release joint and the lateral release surfaces 1. The main driving force acting on the slope is the gravitational force which is directly proportional to the slope inclination. Steeper slope will be more susceptible for instability2. As the upper slope inclination increases, additional rock mass will add to the weight component, thus shearing stresses will increase and instability in the slope will be induced3. Increase in height of the slope will increase the shear stresses4. Further, if potential failure plane daylight on the slope face at an angle smaller to the slope face angle and greater than the angle of friction the kinematic condition is satisfied and failure can take place5. When the shear stress exceeds the shear strength along the potential failure surface, tension crack develops in the upper portion of the slope. The rock mass will tend to detach along this tension crack6 or release joint7. On the either side of the potential sliding mass there must exists lateral release surfaces which provides least resistance to the sliding mass. These release surfaces can be convergent, divergent or planer8.
Plane failure in rock slopes is relatively a simple mode of failure, however it may involve complex failure mechanism owing to its complex geometry9, heterogeneity in geology, non- planer potential failure plane, variability in shear-strength along the potential failure plane10, uneven distribution of the water forces11, surcharge12 and the dynamic loading conditions13.
Detail of Telaga Tujuh, the Seven Wells Waterfall.
How to get there?
You need to hike from the car park. There are two ways to enjoy the waterfall. If you are not too keen climbing and tiring yourself, and you are happy with a quick look of the waterfall, take a short walk up the service road that leads from the car park and take the left turn to reach the bottom of the falls. You will get great view of the fall from here. If you want, you can even bathe at the natural shallow pool. The top of the waterfall can be reached via the same service road, but you go right instead.
Alternatively, you can choose to take the stairs from the car park. There are (only) 638 steps to climb, with signs along the way indicating how many steps remain. When you reach the top of the waterfall, you will find yourself at an altitude of about 480 metres. The pathway goes through the rainforest of Mount Mat Cincang where you will hopefully see lots of flora and fauna including bird life. Some of the amazing fauna includes macaques (don't feed them and watch your belongings), giant squirrels and if lucky even the Great Hornbills with their giant beaks.
From the top of the Seven Wells Waterfall, you can follow a hiking trail that leads to the peak of Mount Mat Cincang. Be warned that it is not an easy trail and not meant for the inexperienced.
The best time to visit the Seven Wells Waterfall, or any waterfall in Malaysia, is during the monsoon season (mid-October - end of March) when you can enjoy their full flow.
Caution is advised.
The rocks at the bottom of the pools can be quite slippery, if you plan on taking a refreshing dip, be careful getting in and out. Last but not least, when on top, do not venture beyond the barricade and warning signs. It is very dangerous and several fatal accidents have taken place here. The drop from here is 65 meters, with no chance of survival.
How to claim this EarthCache?
Email me the following;
1. The text "GC81GQ1 Seven Wells Waterfall - Planar Failure" on the first line.
2. The answers to the following questions;
- Where and how can it be determined that shear stress exceeds shear strength?
- In which direction and at what angle is the upper rock layer sliding?
3. Provide a photo of yourself or a personal item to prove you have visited the site.*
References
* Effective immediately from 10 June 2019, photo requirements are permitted on EarthCaches. This task is not optional, it is an addition to existing logging tasks! Logs that do not meet all requirements posed will no longer be accepted.
For additional information, visit; Geosociety.org, Geocaching.com Help Center and Geocaching.com Forum.
1 Hoek and Bray, 1981. 2 Hamza and Raghuvanshi, 2017; Raghuvanshi et al., 2014. 3 Sharma et al., 1995. 4 Raghuvanshi et al., 2014; Anbalagan, 1992; Hack, 2002. 5 Sharma et al., 1995; Kovari and Fritz, 1984; Hoek and Bray, 1981. 6 Sharma et al., 1995; Hoek and Bray, 1981. 7 Sharma et al., 1999. 8 Sharma et al., 1995; Hoek and Bray, 1981; Price, 2009. 9 Yoon et al., 2002. 10 Tang et al., 2016. 11 Ahmadi and Eslami, 2011. 12 Shukla et al., 2009. 13 Hoek and Bray, 1981.
