ICE TSUNAMI IN THE ALPS - Tambora: The Eruption that Changed the World - page 94

Another literally earth-shattering event, and another moonscape—courtesy of faraway Tam-
bora. Ironically, despite this long-term devastation of the valley, Venetz's success in moder-
ating the flood and ensuring a low death toll meant that his renown would remain local. The
1818 inundation of the Val de Bagnes occupies only a modest place in the rank of nineteenth-
century European catastrophes, a relatively minor instance of the global tsunami of ecological
consequences flowing from Tambora's 1815 eruption. As a turning point in the history of geo-
logy and climate science, however, the Giétro debacle assumes epochal proportions. The geo-
logical impact of the flood impressed Ignace Venetz as proof positive of far deeper historical
processes in the Alps. These processes in turn demanded an entirely new kind of science—one
founded on the concept and historical reality of climate change.
A CATASTROPHE, BUT NOT CATASTROPHISM
Now largely forgotten outside Switzerland, the 1818 Val de Bagnes disaster was nevertheless
widely reported in the European press and became a major talking point in scientific circles.
For those whose information came only from reading reports of the deluge, the event ap-
peared to support the conventional catastrophist theories of geological formation, which, in-
fluenced by the biblical account, emphasized the shaping power of a great flood or floods
that had once submerged the continent and carved out its valleys and mountains. This cata-
strophic diluvian scenario purported to explain the transport of erratic boulders far from their
original location, as well as the thread of moraines at sometimes great distances from the cur-
rent location of Alpine glaciers.
From a distance, the bursting of the River Dranse dam offered a very useful simulation
of large-scale flooding, a kind of test case for catastrophism. Moreover, a selective sketch of
the results proved highly reassuring to catastrophists. High above the valley floor, the Dranse
flood had left new lines of debris that corresponded well with the character of ancient mo-
raines. In addition, its tidal power had detached large boulders from the mountainsides and
dumped them at great distances along the valley. One such block was measured at forty cubic
meters, which, while still only one-tenth the size of the massive Pierre à Bot, the most celeb-
rated of the Alpine erratics, seemed to confirm the transportive power of a massive torrent of
water and mud, and to eliminate the need for any alternative geological explanation. 21
Such, at least, was the general consensus surrounding the Val de Bagnes debacle. But the
closest expert witness to the event, Ignace Venetz, was not convinced. His experience of the
catastrophic flood of 1818 brought him, instead, to the diametrically opposite conclusion:
only glaciers had the power to form the Alps. Two years earlier, he had delivered a paper that
conformed to a traditional theory of erratic boulders transported by rolling on top of glaciers.
By 1821, he had developed the outlines of modern glacial theory and periodic Ice Ages. In
between, he met Jean-Pierre Perraudin and witnessed firsthand the catastrophic flood of the
Val de Bagnes.
Venetz was a brilliantly intuitive geologist but, unfortunately, not a prolific or confident
writer. His 1821 prize-winning paper to the Swiss Society is a rambling amateur affair, im-
mersed in details, but its bullet-point conclusions sketch out, in bold terms, the basic prin-
ciples of modern climate science. Glaciers were nature's own antique ruins, the “relics of
former climates.” 22 “The moraines found at a significant distance from the glaciers,” Venetz