FROST PROBLEMS AND PHOTO INTERPRETATION
Polygons in (a) Sorted and (b) Non-sorted
(including frostcrack polygons, ice-wedge
polygons, tussock-birch-heath polygons, des-
iccation polygons), Steps in (a) Sorted and
(b) Non-sorted and, finally, Stripes in
(a) Sorted and (b) Non-sorted.
Washburn defines Sorted circles as pat-
terned ground whose unit component, the
mesh, is dominantly circular and has a sorted
appearance commonly due to a border of
stones surrounding finer material. Debris is-
lands are sorted circles occurring amid blocks
or boulders. Non-sorted circles are patterned
ground whose mesh is dominantly circular
and which has a non-sorted appearance due
to the absence of a border of stones, such as
that characterizing sorted circles. Sorted nets
are patterned ground whose mesh is inter-
mediate between that of a sorted circle and a
sorted polygon and has a sorted appearance
commonly due to a border of stones surround-
ing finer material. Non-sorted nets are pat-
terned ground whose mesh is intermediate
between that of a non-sorted circle and a non-
sorted polygon and has a non-sorted appear-
ance due to the absence of a border of stones
such as that characterizing a sorted net.
Sorted polygons are patterned ground whose
mesh is dominantly polygonal and has a
sorted appearance commonly due to a border
of stones surrounding finer material. Non-
sorted polygons are patterned ground whose
mesh is dominantly polygonal and has a
non-sorted appearance due to the absence of
Fic. 9. Low-oblique of non-sorted polygons (ice-
wedge polygons) on the coastal plain, Arctic Slope,
Alaska, southeast of Point Barrow, in the con-
tinuous-permafrost zone. Part of thaw lakes top
right and left foreground, a rounded thaw pond
left center. Most of the raised polygons are high-
centered with low ridges around the margin of the
flat-topped polygon. They are confined to rela-
tively well drained areas between lake basins. The
troughs around them are rather wide and some-
times deep as well. Be careful to avoid false relief
with the troughs standing out as ridges. (From a
color photo taken by the author August 15, 1955.
14
Fic. 10. Low-oblique of non-sorted polygons (ice-
wedge polygons) on Arctic coastal plain near
Point Barrow, in the continuous-permaífrost zone,
Alaska. Flat tundra surface. Part of a great thaw
lake at top, angled thaw ponds (high center).
Most of the polygons are high-centered, separated
by shallow troughs. In left foreground and right
center there are several low-center polygons with
ponds developing in their center. (Photo by the
author.)
a border of stones such as that characterizing
sorted polygons.
Depending on usage, synonymous terms
may include fissure-polygons, mud-polygons,
contractional polygons, and others. Ice-wedge
polygons, tussock-birch-heath polygons, vege-
tation polygons and desiccation polygons are
special varieties of non-sorted polygons. The
ice-wedge polygons are characterized by bor-
dering ice wedges. Synonymous terms are
tundra polygons and Taymyr polygons.
Sorted steps are patterned ground with a step-
like form and a sorted appearance due to a
downslope border of stones embanking an
area of finer material upslope. Non-sorted
steps are patterned ground with a steplike
form and a non-sorted appearance due to a
downslope border of vegetation embanking
an area of relatively bare ground upslope.
Sorted stripes are patterned ground with a
striped pattern and a sorted appearance due
to parallel lines of stones and intervening
strips of dominantly finer material oriented
down the steepest available slope. Non-sorted
stripes are patterned ground with a striped
pattern and a non-sorted appearance due to
parallel lines of vegetation-covered ground
and intervening strips of relatively bare
ground oriented down the steepest available
slope. A synonymous term is solifluction
stripes (Washburn).
Britton's excellent paper on ‘Vegetation of
the Arctic Tundra’ (1957), see references, also