Question 1

The  4 former glaciations

Accepted Answer

In 1909, German geologists Albrecht Penck and Eduard Brückner  defined four major quaternarian glaciations, which were all named after tributaries of the river Danube :·        the  Günz Glaciation  from 1,200,000 to 700,000 years BP ;·        the Mindel Glaciation  from 650,000 to 350,000 years BP ;·        the Riss Glaciation  from 300,000 to 130,000 years BP ;·        the Würm Glaciation  from 115,000 to 11,700 years BP.These designations were commonly used throughout  the 20th century, until technological advancements and the collection of scientific data allowed for more meticulous reviews and refining of this chronological breakdown. It is now held for certain that over the last 2.58  million years, this area has known at least 17 glaciations, each of which would  last between  50,000 and 100,000 years, punctuated by shorter interglacial periods generally spanning from 10,000 to 20,000 years.

Question 2

Erratic rocks

Accepted Answer

Pierre pouilleuse, Pierre à 1’000 trous, Bloc monstre, Schüchstein, Druidenstein, Pierres du Niton, Tüfelsburdi : Switzerland teems with hundreds and potentially thousands of erratic rocks. It used to be thought that these huge granite blocks had been transported by torrential waters, until a carpenter from  Val de Bagnes, in Valais, by the name of Jean-Pierre Perraudin, came up with a new theory. By drawing on local knowledge  (a local glacier had once covered  the whole valley and extended to the edges of Martigny) and by observing his immediate surroundings  Perraudin concludes that these boulders must have been brought by glaciers now retreated.His theories gained traction with the science community  as these were reviewed and developed  by engineer geologist Jean de Charpentier and by Louis Agassiz. Pierre-à-Bot derives from a phrase in the local francoprovençal patois  « Piérra a bot ".Louis Agassiz used it to illustrate and present  the glacier theory to the Swiss society of natural sciences and in his book  published in 1837 Discourse on the Ancient Extension of the Glaciers. The following year - and at his request -  the block was classified as a « Precious Monument of Natural Histoiry ». Then, in 1966, a commemorative plaque was  placed to honour the memory of the pionneers of glaciology and geology. And finally, in 1993, a second plaque was placed to celebrate the science club and student society Amici naturae's  hundredth anniversary, whose very first meeting had been held there. A fine record for a 1,352 cubic meters stone which travelled from Valais on the back of a glacier about 20,000 years ago.

Question 3

The Milanković orbital cycles

Accepted Answer

In 1941, Serbian scientist Milutin Milanković shows that climate  variations over tens of thousands of years are linked to the Earth's movements around the Sun. His theory is based on three cycles :Eccentricity : the shape of the Earth's orbit varies in accordance with two cycles (100,000 and 413,000 years), which slightly modifies the Earth - Sun distance. Obliquity : the Earth's axial tilt changes over 41,000 years. This  changes the angle at which the Sun's rays hit the Earth : the steeper the tilt is, the more marked the seasons are. Precession : in the same way as a spinning top, the Earth's axis oscillates slowly over  26,000 years, gradually shifting the seasons on the calendar.These cycles explain the alternation of glaciations and  interglacial periods.

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The 4 former glaciations

Erratic rocks

The Milanković orbital cycles

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