Giétro Glacier
Encyclopedia
The Giétro Glacier or Giétroz Glacier is a 4 km long valley glacier
located in south-western Switzerland
. The 1818 Giétroz glacier catastrophe, which led to lake outburst flood, is one of the most famous and most disastrous historical cases in the Swiss Alps
.
in the Swiss canton of Valais
. It is located in the upper Bagnes Valley, south of Martigny and Verbier
. The length of the glacier is 4.55 km (1979) and its area is 5.85 km² (1979).
The glacier is fed by the snows of Mont Blanc de Cheilon
(3,870 m) and La Ruinette
(3,875 m). On the upper part, the glacier is relatively flat. It descends to the north on the side of Mont Rouge du Giétro and then curves to the west between Le Pleureur
and Mont Rouge. On the lower part, the glacier reaches a steepness of 40% forming a large number of crevasse
s. The terminus
is located at about 2,600 metres. Part of the glacier is linked to the Cheilon Glacier
through the Col du Cheilon (3,243 m). The water generated by the glacier ends in the Lake Mauvoisin (artificial lake) and then reaches the Dranse de Bagnes, a tributary of the Rhone
.
was recorded in 1595 causing 140 deaths. More recently in 1818 a similar lake outburst flood occurred killing 44 people. In the latter case a hole was drilled through the glacier to limit the level of waters.
After an increase of the glacier, an ice cone formed in the valley between 1816-1818. It was created by the accumulation of the falling seracs of the terminus. A lake was formed but it emptied on 27 May 1817, without causing any fatalities. In April 1818 the lake measured about 2 km in length. On 10 May 1818, the engineer Ignace Venetz was called by the canton. To stop the rapid rise of waters, he decided to drill a hole through the ice. The work began one day later. A tunnel was drilled from the two sides, about 20 metres above the level of the lake. An avalanche of ice occurred on 18 May but without any casualties. A secondary tunnel was then drilled for safety reasons. A week later the level of the lake reached 10 metres below the tunnel. On 27 May an enormous piece of ice detached itself from the cone in the lake and floated to the surface while making terrible noise, everybody escaped. They went back to work 2 days later. The 198 metre-long hole was completed on 4 June. Other large pieces of ice detached from the cone and floated back. The waters finally reached the level of the hole on 13 June, 22 p.m. They continued to rise until 14 June, when the level of the lake began to fall because of the erosion of the hole by the waterfall. Some water also ran out from the base of the cone. Only 2 men stayed in place, Venetz warned the inhabitants of the valley of the danger. On the morning of 16 June, terrible noises and violent detonations were heard. The cone began to crack. A group of British tourists and a drawer from Lausanne visited the place with Venetz. In the afternoon, Venetz and the workers escaped to the heights of Fionnay.
Finally, at 4.30 p.m., the dam broke and 18 millions m³ of water invaded the valley. Half an hour later the lake was empty. The flood reached the village of Bagnes 10 minutes later, the alert was given to Martigny before 6 p.m. but too late. The wave invaded Martigny-Bourg a few minutes later. The rise of the waters was observed along the Rhone, at 19 p.m. in Saint Maurice
and at 23 p.m. on Lake Geneva
.
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
located in south-western Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
. The 1818 Giétroz glacier catastrophe, which led to lake outburst flood, is one of the most famous and most disastrous historical cases in the Swiss Alps
Swiss Alps
The Swiss Alps are the portion of the Alps mountain range that lies within Switzerland. Because of their central position within the entire Alpine range, they are also known as the Central Alps....
.
Description
The Giétro Glacier lies on the northern side of the Pennine AlpsPennine Alps
The Pennine Alps are a mountain range in the western part of the Alps. They are located in Switzerland and Italy...
in the Swiss canton of Valais
Valais
The Valais is one of the 26 cantons of Switzerland in the southwestern part of the country, around the valley of the Rhône from its headwaters to Lake Geneva, separating the Pennine Alps from the Bernese Alps. The canton is one of the drier parts of Switzerland in its central Rhône valley...
. It is located in the upper Bagnes Valley, south of Martigny and Verbier
Verbier
Verbier is a village located in southwestern Switzerland in the canton of Valais. It is one of the largest holiday resort and ski areas in the Swiss Alps, is recognized as one of the premiere "off-piste" locations in the world...
. The length of the glacier is 4.55 km (1979) and its area is 5.85 km² (1979).
The glacier is fed by the snows of Mont Blanc de Cheilon
Mont Blanc de Cheilon
Mont Blanc de Cheilon is a mountain in the Pennine Alps in Switzerland. The mountain lies between the valleys of Bagnes and Arolla and is one of the highest summits between the Grand Combin to the west and the Dent Blanche to the east...
(3,870 m) and La Ruinette
La Ruinette
La Ruinette is a mountain in the Pennine Alps. It is the highest summit between the Grand Combin and Dent Blanche. La Ruinette lies close to the better known Mont Blanc de Cheilon which has almost the same height .-External links:*...
(3,875 m). On the upper part, the glacier is relatively flat. It descends to the north on the side of Mont Rouge du Giétro and then curves to the west between Le Pleureur
Le Pleureur
Le Pleureur is a mountain in the Pennine Alps. It is located in Valais, between Lac de Mauvoisin and Lac des Dix....
and Mont Rouge. On the lower part, the glacier reaches a steepness of 40% forming a large number of crevasse
Crevasse
A crevasse is a deep crack in an ice sheet rhys glacier . Crevasses form as a result of the movement and resulting stress associated with the sheer stress generated when two semi-rigid pieces above a plastic substrate have different rates of movement...
s. The terminus
Glacier terminus
A glacier terminus, or snout, is the end of a glacier at any given point in time. Although glaciers seem motionless to the observer, in reality glaciers are in endless motion and the glacier terminus is always either advancing or retreating...
is located at about 2,600 metres. Part of the glacier is linked to the Cheilon Glacier
Cheilon Glacier
The Cheilon Glacier is a 3 km long glacier situated in the Pennine Alps in the canton of Valais in Switzerland. In 1973 it had an area of 4.56 km².-External links:*...
through the Col du Cheilon (3,243 m). The water generated by the glacier ends in the Lake Mauvoisin (artificial lake) and then reaches the Dranse de Bagnes, a tributary of the Rhone
Rhône
Rhone can refer to:* Rhone, one of the major rivers of Europe, running through Switzerland and France* Rhône Glacier, the source of the Rhone River and one of the primary contributors to Lake Geneva in the far eastern end of the canton of Valais in Switzerland...
.
Glacier catastrophes
The Giétro Glacier is known to have caused many deaths in the valley during historical times. A first glacial lake outburst floodGlacial lake outburst flood
A glacial lake outburst flood is a type of outburst flood that occurs when the dam containing a glacial lake fails. The dam can consist of glacier ice or a terminal moraine...
was recorded in 1595 causing 140 deaths. More recently in 1818 a similar lake outburst flood occurred killing 44 people. In the latter case a hole was drilled through the glacier to limit the level of waters.
After an increase of the glacier, an ice cone formed in the valley between 1816-1818. It was created by the accumulation of the falling seracs of the terminus. A lake was formed but it emptied on 27 May 1817, without causing any fatalities. In April 1818 the lake measured about 2 km in length. On 10 May 1818, the engineer Ignace Venetz was called by the canton. To stop the rapid rise of waters, he decided to drill a hole through the ice. The work began one day later. A tunnel was drilled from the two sides, about 20 metres above the level of the lake. An avalanche of ice occurred on 18 May but without any casualties. A secondary tunnel was then drilled for safety reasons. A week later the level of the lake reached 10 metres below the tunnel. On 27 May an enormous piece of ice detached itself from the cone in the lake and floated to the surface while making terrible noise, everybody escaped. They went back to work 2 days later. The 198 metre-long hole was completed on 4 June. Other large pieces of ice detached from the cone and floated back. The waters finally reached the level of the hole on 13 June, 22 p.m. They continued to rise until 14 June, when the level of the lake began to fall because of the erosion of the hole by the waterfall. Some water also ran out from the base of the cone. Only 2 men stayed in place, Venetz warned the inhabitants of the valley of the danger. On the morning of 16 June, terrible noises and violent detonations were heard. The cone began to crack. A group of British tourists and a drawer from Lausanne visited the place with Venetz. In the afternoon, Venetz and the workers escaped to the heights of Fionnay.
Finally, at 4.30 p.m., the dam broke and 18 millions m³ of water invaded the valley. Half an hour later the lake was empty. The flood reached the village of Bagnes 10 minutes later, the alert was given to Martigny before 6 p.m. but too late. The wave invaded Martigny-Bourg a few minutes later. The rise of the waters was observed along the Rhone, at 19 p.m. in Saint Maurice
Saint Maurice
Saint Maurice was the leader of the legendary Roman Theban Legion in the 3rd century, and one of the favorite and most widely venerated saints of that group. He was the patron saint of several professions, locales, and kingdoms...
and at 23 p.m. on Lake Geneva
Lake Geneva
Lake Geneva or Lake Léman is a lake in Switzerland and France. It is one of the largest lakes in Western Europe. 59.53 % of it comes under the jurisdiction of Switzerland , and 40.47 % under France...
.