Geology Reference
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(a)
(b)
10 mm
10 mm
(c)
N
(d)
Figure 4.23 Thin section of Greenland glacier ice: (a) cross‐polarized light, (b) scattered light, (c) parallel‐polarized
light and (d) the fabric diagram using only the larger grains. Note the effects of different light and imaging condi-
tions on the apparent information in the images (N. K. Sinha, unpublished).
about 11 km east of the calving end of the glacier. The
area was heavily crevassed by streams and melt ponds.
The photographs show different families of air bubbles
with different orientations [bright objects in (b) are the
results of healing processes of cracks]. The rectangular‐
shaped rows of crystals lined up diagonally [particularly
visible in (a)] indicate that a large crack developed at
some time, and the void was filled probably by the melt-
water, which eventually solidified and produced two rows
of large crystals. These grains along with other large
grains in the thin section were used to make the fabric
diagram. The marking N indicates the top of the micro-
graphs and the direction parallel to the smaller dimen-
sion of the images. The orientations of the polarizers are
shown by the pair of double‐headed arrows in (a) (cross
position) and (b) (parallel position with the polarizer
making 30° from the direction, N. The fabric diagram in
(d) may not be significant in a statistical sense because it
does not include a large number of grains.
4.3.4. Stereographical Projection (Fabric Diagram)
of Natural Polycrystalline Ice
One of the important aspects of natural ice is the over-
all crystallographic orientation of the c axis of the constitu-
ent crystals. They can be oriented in any direction in the
3D space. The stereographic projection is a useful tool for
mapping the crystallographic planes and directions in
terms of c axis of the ice grains in two dimensions: the
azimuth angle and the inclination angle (direction of
inclination as to left or right). It allows the visualization
of the orientations of the crystallographic planes and
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