The legend of the Wizard of Alderley Edge has been around for centuries, retold in slightly different forms. But this EarthCache, written to celebrate GeoWeek 2024, suggests a different type of magic that can be better explained by ‘geoscience’ than ‘sorcery’.
The geology focuses on a prominent impermeable mudstone layer of rock at two waypoints close to each other at Wizard's Well. (This layer is also seen at the EarthCache ‘Minor Fault on the Edge’ GC8KFFH).
Figure 1
Directions
The co-ordinates will take you to the two locations where you will find the answers to 5 task questions. (You are reminded of the need for care and to follow the National Trust requests on local information boards to keep this place special by following the Geological Fieldwork Code).
From a parking layby at on the Macclesfield Road (SJ 855779) take the short National Trust path northwards towards Castle Rock (site of another Earthcache GCZZP6P). Alternative parking is available on the Macclesfield Road at a rough parking area near Beacon Lodge (SJ 858775) which provides direct access to another EarthCache at Great Quarry should this be included on a longer circular walk (GC8KFFH ‘Minor fault on the Edge’). See Figure 1.
A short diversion from this path to the top of Castle Rock is well worth the effort with excellent views across the Cheshire Plain towards Manchester and the Pennines (care is needed at the significant cliff drop). Return to the path and on reaching the Edge take the left-hand path for 100 m towards Wizard’s Well until reaching Waypoint 1.
Waypoint 1:
Figure 2
Before reaching the Wizard’s Well it is worth examining the small rock cut at the side of the path (SJ 85509 78050). Figure 2. Here, a mudstone bed is exposed, similar to that seen in Great Quarry, also dipping at about 15°. The mudstone is less resistent than the sandstone layers above and below and has been eroded more. A close inspection of the underside of the overlying sandstone bed reveals some excellent evidence that this rock formed when rivers overflowed onto a floodplain depositing mud and clay which rapidly dried in the hot Triassic sun, some 230 million years ago. At this locality the cast of a reptilian footprint was once identified. This suggests that early dinosaurs once walked across this muddy surface and their footprints, baked hard in the hot sun, where preserved when they were later infilled by sand from a river. Sadly there is no evidence of the footprint today though it is always worth a look!
Waypoint 2 - Wizard’s Well (SJ 855780)
Figure 3
Follow the path 25m further down the track to where the mudstone is exposed again at Wizard’s Well (Figure 3). Here a permanent spring forces water to the surface, some 70 m above the main water table on the plain below. A diagram to explain the ‘perched water table’ is illustrated in Figure 4.
A steep face immediately to the right of the well trough is a fault plane, dipping 62°, which can be identified by scratches on the rock surface called ‘slickensides’, formed as the rocks ground past each other during an earthquake.
Wizards Well is overlooked by the face of the Wizard himself! Can you find him? The carved inscription below reads:
'Drink of this and take thy fill for the water falls by the Wizhard's will'
Figure 4
Logging details
To log this EarthCache please send the answers to the two sets of tasks via email or through the Message Centre.
Tasks at Waypoint 1
- The beds at this locality are dipping at about 15°. Using a compass or the map in Figure 1, state in what direction the beds at this locality are dipping.
- The following pictures represent sedimentary structures commonly found at the base of beds which reflect the upper surface of the bed that formed directly below.
State which of the photos (A, B, C or D) is most likely to represent the sedimentary structures seen at the base of the overlying sandstone at this locality.
- Describe a situation where this sedimentary structure might be forming today.
Tasks at Waypoint 2
- Take a small piece of the red mudstone layer seen at the path level to the left of the water trough (see Figure 3). Squeeze it between your fingers, describe what happens and suggest why.
- With reference to Figure 4, explain why there is a spring at this location, 70 metres above the normal height of the main water table.
- As an option, it would be good if you could post a photo of the Wizard's face so we can scientifically record the weathering of this feature and its change over time. Other photos also welcome.