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

It is 19 m long, 10 m wide and 9 m high with a volume of 1800 cubic metres, and has a small building on top of it, constructed in the second half of the 19th century, together with steps to reach it. It was deposited here by the Rhone Glacier, around 18,000 years ago. I was standing on a railway track that runs past the hospital to take this photo. As a footnote, some years ago I caught a train that took this track to get to a ski resort. As I passed the hospital building, I was looking straight into a large window not very far from the train through which I could see an operation in progress and the insides of the patient who was being cut open.

Another view of La Pierre des Marmettes from the other side.

The second erratic “La Pierre à Dzo” is perched on three other granite boulders, the granite coming from the Mont Blanc Massif about 30 km away and quite different to the local limestone. In the 18th century, these erratics were believed to have been transported by the biblical Flood.
A local hunter Jean-Pierre Perraudin (1767-1858) became convinced that these erratics had been transported by glaciers in the past and in 1815 described his theory to Jean de Charpentier (1786-1855), a geologist who ran the local salt mine. This was also the period in which Scottish geologists Hutton and Lyell were realising the huge extent of geological time.

La Pierre à Dzo

The above photo is from my first visit in January, when it was cold and raining. I also include below some more recent photos from a second visit in September, in sunny autumn weather.

The third erratic, La Pierre à Muguet is  the second largest at 25 metres long and 15 metres wide 7 metres high, 1000 cubic metres of volume and is also perched on underlying blocks.

The passage under La Pierre à Mugue is large enough to walk through

Inscription on the boulder below La Pierre à Mugue mentions Perraudin and de Charpentier, who first recognized the glacial origin of these erratics.

Charpentier found additional evidence for the glacial theory, and used the locations of erratics to map the former extent of the Rhone Glacier during the last Ice Age. At its peak, 23,000 years ago, it extended about 20 km south of Geneva. There are two erratic blocks sticking out of the lake, just near the Mont Blanc bridge in the centre of town.

I found an 1842 review of Charpentier’s essay outlining his arguments that glaciers created the Rhone Valley and the formation of the erratics:

“M. de Charpentier mentions many blocks of granite from 40,000 to 100,000 cubic feet, and as an exception to the general rule, a b lock of limestone, the largest known, situate near Bex which contains 161,000 cubic feet. These blocks must have travelled a great distance, some of the 25 and even 60 leages, from the place of their origin”.   Essay on the Glacers and the Erratic Formation of the Basin of the Rhone. By Jean de Charpntier [Review]. The Edinburgh New Philosophical Journal, 1842. Volume 33, page 119.

 

Looking north towards the Rhine Valley from La Pierre à Muguet

We also went to the other side of the Rhone Valley to visit a giant’s kettle. A giant’s kettle, also known as either a giant’s cauldron, moulin pothole, or glacial pothole, is a typically large and cylindrical pothole drilled in solid rock underlying a glacier either by water descending down a deep moulin or by gravel rotating in the bed of subglacial meltwater stream. “La marmite glaciaire des Caillettes” was created by the Rhone Glacier 17,000 years ago during the last ice age and is 5 metres in diameter and 8 metres high.  It is nestled in a cliff above some farmland about a hundred metres above the current level of the Rhone River near Bex in the Valais.

La marmite glaciaire des Caillettes

It was created by the subglacial meltwater stream under the glacier, then around 1200 to 1600 m of ice thick (4000 to 5000 feet). The pressurized meltwater, full of gravel, flowed over a cliff where a crack or fissure created a vortex in the water, drilling a hole into the bedrock. Although known and mentioned several centuries ago, until recently it was filled with boulders and rubble. During the 1960s, some local people got together and spent a year of weekends cleaning all the boulders and rubble out of it. Dynamite and hoisting gear had to be used to get some of the larger boulders out of the bottom.

Looking down into La marmite glaciaire des Caillettes.

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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.

The pyramids form a line down to the river at the bottom of the valley. In the distance about 12 km away is the Rhone Valley. Turn left and it is about an hour and half drive to Geneva on the motorway. The glaciers retreated around 11,000 years ago. These capstones have been sitting there for a long time. Heavy rainfall in big storms caused a number of landslides and undercutting of some of the towers in January this year. They may not be around for much longer.

Canoeing in the Noosa Everglades

While visiting Noosa in July, I took my two boys on a kayak trip into the Noosa Everglades.  Located in the Great Sandy National Park, the upper reaches of the Noosa River are a network of waterways, rivers, lakes and marshes and are best explored by kayak or canoe. The Everglades are situated in the Noosa Biosphere, which is one of Australia’s most diverse ecosystems and includes more than 40 per cent of the country’s bird species.

We drove about 20 km from Noosa to Booreen Point on Lake Cootharaba and crossed the lake in a larger boat to the mouth of the Upper Noosa River, where we changed to canoes, and continued into the Everglades by canoe. Lake Cootharaba is one of three large lakes connected to the Noosa River, the others are Lake Cooroibah and Lake Weyba.

Lake Cootharaba

The banks of the river are a mix of swampy grassland and subtropical forest, with patches of rainforest. There are lots of banksia trees and tea-trees. The tea-trees stain the water a deep brown colour from the tannin in their leaves. The Tea Tree, Melaleuca alternifolia, is an Australian native plant, and its leaves are also used to produce tea-tree oil, prized for its it’s anti-bacterial and anti-fungal prowess.

Upper Noosa River

 

When we reached the historic Harry’s Hut, we stopped for a swim in the river. Under the water, it looks as though we are swimming coca-cola, and more than a metre or so down, it is essentially black, as no sunlight penetrates the tannin-saturated water.

Known as the River of Mirrors because of the amazing reflections in the water, the Noosa Everglades is a 60km stretch of pristine waters, magnificent flora and fauna and narrow waterways.

Most of the information online about the Noosa Everglades describes it as one of the only two Everglades in the world – the other being the much better known Florida Everglades. Various definitions of Everglade are given, most refer to subtropical wetlands characterised by swampy grasslands and branching waterways. I thought it was implausible that there would only be two Everglades in the world.  I did some research via Dr Google, and my conclusion is that “everglades” is not a technical term for a particular type of ecosystem as I initially assumed, but is a made up name that was given to the Florida Everglades.  One of the early English surveyors in Florida coined the name “River Glades” using the word “glade” which is a Middle English word meaning a “bright space, an open space; an open or cleared space in a forest. This was later changed to “Everglades.  I also found a website that said it is thought the term Everglade was first used to describe part of the extensive water way and wetlands of the Noosa River by tour guides, presumably hoping to piggy-back on the well known Florida Everglades.

And I think it is only in Australia, that the Noosa Everglades are considered “one of the only two”.  According to Answers.com and many American websites, there is only one Everglades in the world.  The Florida Everglades are about 100 miles long, and cover 1900 square kilometres.  The Noosa Everglades are about 60 km long, and cover around 700 square kilometres.  So my rough calculation says that the Noosa Everglades is about one third the size of the Florida Everglades.

As we returned across Lake Cootharaba at the end of the day, we were told that the local Aboriginal tribe told early settlers that in ancient times there were two large stone statues, rather like the Easter Island statues, on the shore of the lake.  Maybe that is just a story for the tourists, maybe the statues are buried in the sand somewhere in the sandhills between the lake and the ocean.

WW1 Diaries of Tom Mathers – extracts on the Battle of the Somme 1916

Just over 100 years ago my grandfather Will Mathers and his brother Tom, both in the 8th Australian Field Ambulance, took part in the Battle of the Somme, on the front line from 18 September 1916 to 8 November.

The Battle of the Somme, also known as the Somme Offensive, was fought by the armies of the British and French empires against the German Empire. It took place between 1 July and 18 November 1916 on both sides of upper reaches of the River Somme in France. It was the largest battle of the First World War on the Western Front; more than one million men were wounded or killed, making it one of the bloodiest battles in human history. Tom kept a diary throughout the war [see Endnote 1] and his diary account provides a terse but graphic account of the experience of being a stretcher bearer on the front lines.

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