Part 2 Dangereous areas on glaciers€¦ · • Crevasses (cracks in the surface) • Melt water...
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Part 2 Dangerous areas on glaciers Photo: K. Bælum
Transcript of Part 2 Dangereous areas on glaciers€¦ · • Crevasses (cracks in the surface) • Melt water...
Part 2 Dangerous areas on glaciers
Photo: K. Bælum
Dangerous areas on glaciers
• Crevasses (cracks in the surface)
Photo: Wikipedia
ICEICE
Where and why do crevasses form?
Illustration: K. Bælum
Compression = deformation (some times fractures)
Illustration: K. Bælum
Illustration: K. Bælum
Illustration: K. Bælum
Extension = Fractures
Illustration: K. Bælum
Illustration: K. Bælum
Photo: K. Bælum
Shear = fractures
Illustration: K. Bælum
Illustration: K. Bælum
Photo: K. Bælum
Uplift = fractures
Illustration: K. Bælum
Illustration: K. Bælum
Photo: K. Bælum
Dangerous areas on glaciers
• Crevasses (cracks in the surface)• Melt water channels
– Most glaciers have melt water channels, some have many, some few
– They may not always be covered with sufficient snow – especially not in early winter
– They can be 10-20m deep.
Melt water channels in late autumn
Melt water channels
A recent melt water channel accident fortunately ended well
Dangerous areas on glaciers
• Crevasses (cracks in the surface)• Melt water channels• Moulins (glacier wells, big holes in the glacier
surface)
Dangerous areas on glaciers
Photo: M. Sund
10 m
Waterfall
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– Found in front of glaciers
– They can occur even at very low temperatures
– Some of the water may be frozen, but liquid water may also be covered by snow or a thin ice layer.
Photo: M. Sund
Don't park your scooter overnight in front of a glacier!
Photo: R. Behlke
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
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 glacierMelt water channels.
Melt water/icing at the front, even in winter.
Moulins (glacier wells)
Ice flows downhill.
Illustration: K. Bælum
600m
500m
400m
300m
Illustration: K. Bælum
90°
General rule - Ice flows downhill, perpendicular to the contour lines
Some of the problem areas can be identified from a map
Extensional stress
Bergscrund and meltwater channels
Lakes on the surface
Transverse stress
Uplift areas
Front of glacier
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!
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
