Glacial Erratic Blocks in the Rhone Valley

Continuing our glacial explorations (see also The-pyramids-of-euseigne), we visited a number of enormous glacial erratic blocks in the wooded slopes above the town of Monthey in the Rhone Valley. These blocks played a pivotal role in the realization that there had been great Ice Ages in the past. There are eight blocks along a trail about 5km long between Monthey and Collombey. ( MT_Blocs_Erratiques_Web.pdf). The first and largest of these blocks, “La Pierre des Marmettes”, is now in the middle of the parking lot of the Monthey Hospital.

La Pierre des Marmettes

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The Pyramids of Euseigne

The Pyramids of Euseigne are one of the more bizarre geological features created by the last ice age. They are in the Val d’Hérens, one of the southern side valleys off the Rhône valley of Switzerland. The entire Rhone valley and its side valleys were under glaciers at the height of the last ice age around 23,000 years ago. An old university friend who is a geologist visited Switzerland at the beginning of the year and invited me to join him for an exploration of some of the landscape features created by the glaciers of the last ice age.

In the photo below, my friend is looking south towards the junction of the Val d’Hérens and Val d’Hérémence where two glaciers met and continued down towards us. The pyramids are located on the ridge separating the two valleys, We are standing on the remnants of a glacial lake delta formed by the damming of the melt waters of the joined glaciers. The glaciers retreated about 11,000 years ago when humans expanded north back into Northern Europe and Britain again.

The Pyramids are the remnants of a ground moraine created from finely ground silt and sand with embedded larger boulders. Some of the boulders protected the underlying compacted silt from erosion, forming protective caps.

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