Dangerous areas on glaciers

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Part 2 Dangerous areas on glaciers

Photo: K. Bælum

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Dangerous areas on glaciers

• Crevasses (cracks in the surface)

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Photo: Wikipedia

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ICE ICE

Where and why do crevasses form?

Illustration: K. Bælum

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Compression = deformation

(some times fractures)

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Extension = Fractures

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Photo: K. Bælum

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Shear = fractures

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Photo: K. Bælum

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Uplift = fractures

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Photo: K. Bælum

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Dangerous areas on glaciers

• Crevasses (cracks in the surface)

• Melt water channels

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Most glaciers have melt water channels, some have many, some few

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They may not always be covered with sufficient snow – especially not in early winter

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They can be 10-20m deep.

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Melt water channels in late autumn

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Melt water channels

A recent melt water channel accident fortunately ended well

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Dangerous areas on glaciers

• Crevasses (cracks in the surface)

• Melt water channels

• Moulins (glacier wells, big holes in the glacier

surface)

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Dangerous areas on glaciers

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Photo: M. Sund

10 m

Waterfall

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Dangerous areas on glaciers

• Crevasses (cracks in the surface)

• Melt water channels

• Moulins (glacier wells, big holes in the glacier surface)

• Melt water/ Icings in front of the glacier, summer and winter

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Found in front of glaciers

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They can occur even at very low temperatures

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Some of the water may be frozen, but liquid water may also be

covered by snow or a thin ice layer.

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Photo: M. Sund

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Don't park your scooter overnight in front of a glacier!

Photo: R. Behlke

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Dangerous areas on glaciers

• Crevasses (cracks in the surface)

• Melt water channels

• Moulins (glacier wells, big holes in the glacier surface)

• Melt water in front of the glacier, summer and winter

• Steep mountain sides around the glacier, falling

rocks and avalanches

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Outside of turn, Marginal crevasses

Inside of turn, compaction Steep section, icefall,

Extensional crevasses

Front and sides of glacier, marginal crevasses

Widening of the cross profile.

Extensional crevasses along flow lines Narrowing of the cross profile,

transversal crevasses

Dome on the bed rock, uplift.

Chaotic crevasse pattern Below mountainside,

Bergschrund.

Along sides, and on the glacier Melt water channels.

Melt water/icing at the front, even in winter.

Moulins (glacier wells)

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Ice flows downhill.

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600m

500m

400m

300m

Illustration: K. Bælum 90°

General rule - Ice flows downhill,

perpendicular to the contour lines

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Some of the problem areas can be

identified from a map

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Extensional stress

Bergscrund and meltwater channels Lakes on the surface

Transverse stress Uplift areas

Front of glacier

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Extensional stress

Bergscrund and meltwaterchannels Lakes on the surface

Transverse stress Uplift areas

Front of glacier

Remember: This is just a map not the

real thing!

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IMPORTANT:

Svalbard maps are partly based on old aerial photos – the glaciers could have change a lot

during this time (e.g. surges) !

The newest maps available still have 13 to 18 years old glacier data