54
Climatic Geomorphology
~,~
Glacier
~~~
> movement .... ~"
(a)
t~~..-)...-~..~
Equilibrium line
I
s i ' , ;
: :
T7"~%~-~,--_ Glacier surface i
I ~
' '
li
t!
'l
"1 li
!
I
I
I |
e.,
I ,
I |
I 9
" t
_ _ ~
llllllllllllllII!!llllllllllll ....
(b)
~ Extending
~ Compressive
Figure 2.23. (a) Compressive and extensive flow and sliding planes. (b) Distribution of compressive and
extensive flows in a glacier (Nye, 1952).
In the accumulation areas stratification predominates, marked by an alternation of
winter and summer ice layers containing sediment formed in the summer melting.
During glacial flow, planar foliation structure originates and can be recognized by the
grain of the ice with alternation of clear blue ice bands and white ice with air bubbles,
with these last being the most abundant ones (Sharp, 1988). These bands vary in their
dimensions from millimetres to several metres. Foliation has a greater development next
to the walls of valleys, where it runs parallel to the rocky outcrops. It is arranged in
cross-section with the direction of the ice flow far from the margins and near the glacier
terminus (Rutter, 1965). Sometimes it is difficult to distinguish the stratification of the
foliation where it is parallel to sedimentary layers.
Commonly glaciers appear folded and faulted (Hambrey, 1977), where it is possible to
observe these structures on the glacier surface and in marginal cliffs (Fig. 2.24). Folds
have different sizes and directions and are very evident in glaciers with surging flows
(Fig. 2.22) as well as in some piedmont glaciers, such as Malaspina Glacier where great
folds similar to those affecting moraines and ice bands are observed (Fig. 2.19).
In steep sloped zones of a glacier, gravity faults and rotational slidings can develop.
At the glacier terminus and where the advance of the ice is interrupted by moraines they
produce thrust planes.
Climatic Geomorphology
~,~
Glacier
~~~
> movement .... ~"
(a)
t~~..-)...-~..~
Equilibrium line
I
s i ' , ;
: :
T7"~%~-~,--_ Glacier surface i
I ~
' '
li
t!
'l
"1 li
!
I
I
I |
e.,
I ,
I |
I 9
" t
_ _ ~
llllllllllllllII!!llllllllllll ....
(b)
~ Extending
~ Compressive
Figure 2.23. (a) Compressive and extensive flow and sliding planes. (b) Distribution of compressive and
extensive flows in a glacier (Nye, 1952).
In the accumulation areas stratification predominates, marked by an alternation of
winter and summer ice layers containing sediment formed in the summer melting.
During glacial flow, planar foliation structure originates and can be recognized by the
grain of the ice with alternation of clear blue ice bands and white ice with air bubbles,
with these last being the most abundant ones (Sharp, 1988). These bands vary in their
dimensions from millimetres to several metres. Foliation has a greater development next
to the walls of valleys, where it runs parallel to the rocky outcrops. It is arranged in
cross-section with the direction of the ice flow far from the margins and near the glacier
terminus (Rutter, 1965). Sometimes it is difficult to distinguish the stratification of the
foliation where it is parallel to sedimentary layers.
Commonly glaciers appear folded and faulted (Hambrey, 1977), where it is possible to
observe these structures on the glacier surface and in marginal cliffs (Fig. 2.24). Folds
have different sizes and directions and are very evident in glaciers with surging flows
(Fig. 2.22) as well as in some piedmont glaciers, such as Malaspina Glacier where great
folds similar to those affecting moraines and ice bands are observed (Fig. 2.19).
In steep sloped zones of a glacier, gravity faults and rotational slidings can develop.
At the glacier terminus and where the advance of the ice is interrupted by moraines they
produce thrust planes.