Pietra Alta
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Pietra Alta
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 The Pietra Alta, in the background Monte Musinè | |
  Pietra Alta | |
| Coordinates: 45°06′45″N 7°29′44″E / 45.11242°N 7.49547°E | |
| Location | Near Caselette, (TO) |
| Geology | Glacial erratic |
| Elevation | 368 m (1,207 ft) |
The Pietra Alta (in piedmontese: Pera Aota or Peraota,[2][3] meaning High Stone) is a glacial erratic in the comune of Caselette (TO, Italy), relevant for its size and its isolated location.[4]
The erratic is a massive boulder with a pyramidal shape,[5] emerging some 10 metres from the ground level and with a circumference of about 50 metres.[6] Its elevation is 368 m.[1] It stands in a woody and almost plain spot close to the border between Caselette and Alpignano,[4] not faraway from the small Lake of Caselette.[1] The place is still of a good environmental quality, although almost encircled by industrial and residential areas.[2]
Geology
The Pietra Alta belongs to the Morainic amphitheater of Rivoli-Avigliana,[7] and in particular to the moraine left by the Riss glaciation. It was transported to its present location by the hudge glacier which occupied the Susa Valley.[6]
Its height on the ground level, remarkable if compared to other glacial erratics of Piedmont, can be explained because the Pietra Alta, unlikely other boulders mostly covered by the ground, is almost fully exposed.[8] It consists in a huge block of serpentinite[9] with a volume of 2.600 cubic metres.[4] On its surface can be detected rinds similar to the so-called desert varnishes, considered by geologist an indicator of a semi-arid climate.[10]
