It consists of a slice of the hillside that has been separated from the main slope. This has created a narrow chasm which visitors can walk. It has commonly been explained as result of glacial plucking, but more recent research indicates that a translational landslide was the cause. During an ice age, a glacier slowly undermined the crag, opening up cracks in the rock and causing this chasm to form. A slide-type landslide is a down-slope movement of material that occurs along a distinctive surface of weakness such as a fault, joint or bedding plane (see below). If the slip surface is straight then it is termed translational or planar.
A fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock mass movement.
A joint is a break or fracture of natural origin in the continuity of either a layer or body of rock that lacks any visible or measurable movement parallel to the surface (plane) of the fracture. Joints are among the most universal geologic structures as they are found in most every exposure of rock. They vary greatly in appearance, dimensions, and arrangement.
Faults differ from joints in that they exhibit visible or measurable lateral movement between the opposite surfaces of the fracture. As a result, a joint may have been created by either strict movement of a rock layer perpendicular to the fracture or by varying degrees of lateral displacement parallel to the surface (plane) of the fracture that remains “invisible” at the scale of observation.
A bed is the smallest division of a geologic formation series marked by well-defined divisional planes (bedding planes) separating it from layers above and below. A bed ranges in thickness from a centimetre to several metres and is distinguishable from beds above and below it. Beds can be differentiated in various ways, including rock or mineral type and particle size.
The rock at the Whangie is Calciferous sandstone, a geological term relating to strata (a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers) at the base of the rock formation, below the entire sequence of coal measures. Typically this rock contains a mixture of lavas and sedimentary rocks, including sandstone and mudstone.
To log this EarthCache go to the listed coordinates and carry out the following tasks. The answers MUST be sent to us via email or message. IF ANSWERS ARE NOT RECEIVED WITHIN 4 WEEKS OF LOGGING IT WILL BE DELETED WITHOUT NOTIFICATION.
1. What is your estimate of the length and height of the chasm.
2. Please tell us where the narrowist bit of the chasm is eg. end nearest coords, middle or further away, or was it all a similar width?
3. Which direction did the land slide?
4. Why do you think geologists now believe the area to have been caused by a landslip and not glacial plucking (you may need to google this if you don't know what the later is)?
5. Please attach a photo to your log of you, your dog, gps, thumb or something personal to prove you were here. Please do not show any spoilers in your photo.
June 2019 the logging tasks for EC were updated. COs can now insist on a photo as proof of visit.
PLEASE BE EXTREMELY CAREFUL IF YOU CHOOSE TO CLIMB ON THE ROCKS.
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