Part 2
Dangerous areas on glaciers
Photo: K. Bælum
Dangerous areas on glaciers
• Crevasses (cracks in the surface)
Photo: Wikipedia
Where and why do crevasses
form?
ICE
ICE
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
Waterfall
10 m
Photo: M. Sund
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
Below mountainside,
Bergschrund.
Along sides, and on the glacier
Melt water channels.
Dome on the bed rock, uplift.
Chaotic crevasse pattern
Steep section, icefall,
Extensional crevasses
Outside of turn,
Marginal crevasses
Inside of turn,
compaction
Narrowing of the cross profile,
transversal crevasses
Widening of the cross profile.
Extensional crevasses along flow lines
Moulins (glacier wells)
Front and sides of glacier,
marginal crevasses
Melt water/icing at the
front, even in winter.
Ice flows downhill.
Illustration: K. Bælum
0m
60
General rule - Ice flows downhill,
perpendicular to the contour lines
500m
40
0m
90°
30
0m
Illustration: K. Bælum
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
Remember: This is just a map not the
real thing!
Extensional stress
Bergscrund and meltwaterchannels
Lakes on the surface
Transverse stress
Uplift areas
Front of glacier
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