Page 44 - DIVA_No.18_2005

U Geneva

GENEVA

The last 2.5 million years of the Würm. both glaciers bumping into each
Earth's history (in geological The Würm Glaciation, for other in the region of
terms, very recently!) have been example, is believed to have Annemasse. Then, about 20,000
remarkable for a succession of started some 70,000 years ago. years ago, the fluctuations in
Ice Ages when enormous gla- At its maximum extent, about the Earth's orbit that were at the
ciers spread over a large part of 25,000 years ago, all the Alpine origin of the Ice Age favoured a
the Earth's surface—and then valleys were completely filled general warming, although this
disappeared. It is believed that with ice pouring out from the took place in a series of warmer
there have been some twenty high mountains and flowing and colder waves. As the cli-
Ice Ages that have come and onto the plains, where it spread mate warmed up, the Rhone
gone during this period, each out into vast fan-shaped ice Glacier became narrower allow-
one lasting about 100,000 years. deltas. Based on the evidence of ing a tongue of the Arve Glacier
It is difficult for us today to rocks deposited by the ice, the to penetrate through the
imagine how extensive these front of the joint Rhone-Arve Annemasse gap into the Geneva
glaciers were: a quarter of the Glacier reached as far as Satolas region and along the base of the
land in North America and on the outskirts of Lyon. At its Saléve as far as Bardonnex.
Europe was covered to a depth height, the Arve Glacier was 2.2 However, by 16,000 years
in places of two or three kilo- km deep above Chamonix. The before the present, the glaciers
metres. In the Northern Rhone Glacier filled the entire had melted from the plains. The
Hemisphere some 50 million basin occupied now by the Lake level of the lake of Geneva was
cubic kilometres of water were of Geneva, the ice being 1,200 higher than at present. The first
locked up in these ice sheets, metres thick above Geneva plants began to find a foothold
exactly like those covering itself, thus covering the Salève. on the chaotic landscape con-
Greenland today. So much (Traces of the previous glacia- taining a multitude of small
water lay frozen that the level of tion—the Riss—can also be lakes left behind by the retreat-
the oceans dropped by 120 found on top of the Salève!) ing glaciers. The new vegeta-
metres. The Alps still bear the The Arve Glacier flowed down tion, willow and juniper,
traces of the last two Ice from Mont Blanc and went attracted animals—mammoths!
Ages—called the Riss and the round the back of the Salève, After the ice had retreated from

46 Diva 1.2005