The Picnic Hill - the cherry on the top EarthCache
The Picnic Hill - the cherry on the top
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Walking the various paths around St. Magdalene's HIll on the southern edge of Perth takes you up towards a viewpoint and a large glacial eratic boulder.
St Magdalene’s Hill is located on the mid and upper slopes of a range of low hills west of Perth at between 50 and 150 m height and includes the summit of St Magdalene’s Hill and part of Hilton Hill.
The Hill is made up of andesite ( a grey, fine-grained volcanic rock) and basalt larvas ( a hard dark grey/black rock) that underly most of the Ochils and parts of the Sidlaws along the Rift Valley.
The rift valley is the result of volcanic activity during the Carboniferous Period ( period when beds of coal were laid) , sculpting the landscape into low rolling hills that are the Ochils and Lommonds that you see today. The bedrock comes very close to the surface in many areas of St Magdalene’s Hill, erupting as small crags and smooth surfaces to walk over as you explore around the hill.
The rest of the site is overlain by a layer of Quaternary (period when glaciation took place) deposits which is deep in hollows, but generally surprisingly shallow. Glacial silt is very fertile, thus the rich diversity of trees that can be found around the hill. If you look to the east, you can see the traditional U shaped glacial valley of the Carse of Gowrie, with the River Tay meandering through, famous for its soft fruits which grow well on the fertile glacial soils.
On a number of occasions during the last two million years Tayside, like the rest of Scotland, has been covered by kilometre-thick ice-sheets. The build up of the last main ice sheet dates to about 28,000 years ago. The ice, which originated in the Highlands flowed south and eastwards through the major Glens of Tayside. As the glacier melted it deposited its rich silt and stones, pebbles along the way and included glacial erratics/boulders carried some considerable distance, recognisable by their totally different colours.
A glacial boulder has distinct rounded edges, caused by the force of the ice age pushing it along in its glacial flow. These erratics can vary in size from huge boulders to small pebble deposits. Some hillsides can be littered with boulders, and others you will be lucky just to spot the odd one or two. They are called erratics as they are a completely alien type of rock to the surrounding area, dependant upon the distance they have travelled and often showing deep battlescars of their journey. Large erratics are very popular with climbers, who like to practice their bouldering techniques by holding onto the cracks with their chalk covered fingers as they try to get to the top, using a thick crash mat below them should they fall. This erratic is not as large, but unusual in that it is the only one on the hillside, and makes a good viewpoint for visitors on the hill to visit.
LOGGING INSTRUCTIONS
1. Look at the erratic boulder. Estimate the approximate circumference of the boulder at its widest point and also list what 'battlescars' of its glacial journey you can see.
Do not mention these findings on your log but please email or message your answers back to me. Once you have done so you are welcome to log the cache.
2. If you wish you may also take a photo of one of your team or your GPS with the erratic boulder and add to your online log. Any other photos of your view from the stone will be welcome.
Additional Hints
(Decrypt)
Ab nafjref, ab svaq.