PHOTOGRAMMETRIC ENGINEERING
FiG. 11. Ground photo of mon-sorted polygons
(ice-wedge polygons) in the continuous-perma-
frost zone near Barrow, Arctic coastal plain of
Alaska. Flat to high-centered polygons with shal-
low troughs (upper center); 'Alaska Cotton"
(Eriophorum Scheuchzeri), center; Mud cracks
(foreground). (Photo by the author August 19,
1
J.
deals with the conspicuous ground patterns
on the Coastal Plain, the ice-wedge polygons.
Depending especially on differences in distri-
bution and permanency of standing waters
and the distribution of vegetation types, the
surface of the polygons may vary in many re-
spects. According to the origin, growth and
decay of the polygons, i.e. their gradational
forms, the features will change from flat sur-
face with cracks to low-centered polygons,
and, finally, to high-centered polygons. Low-
center polygons are characteristic of the wet-
test terrain and high-center ones of the best
drained slopes. Ridged polygons are ice-wedge
polygons with low ridges around the margin
of the polygon.
In the Swedish Arctic region, especially on
permanently frozen peat-bogs, there are
dome-shaped hillocks generally 10-13 feet
high (observed maximum 23 feet) composed
of a core of massive ice or ice-impregnated
peat covered by about 3 feet of insulating
peat and moss species. They are called ““pal-
sar" and may be compared with the Alaskan
isolated, steep-sided, symmetrically rounded
mounts or hillocks called pingos. These may
attain a height of 10 to 100 feet or more, and
are prominent features on the Arctic plain.
DISTRIBUTION OF PATTERNED GROUND
Patterned ground occurs not only in polar,
subpolar, and alpine regions, but even in
many other areas of the world, where climate
and terrain favor frost action. A typical ex-
ample of a more or less unexpected area of
patterned ground is the low-leveled island
Oland in the southern Baltic Sea at the east
coast of Sweden. Oland is known for its silu-
rian-ordovician limestone layers, its mild cli-
mate in summer and fall but with relatively
cold winters. There occur perfect developed
patterned ground with sorted as well as non-
sorted nets and polygons, well worth a care-
ful study (Rydquist, 1957). Troll, too, see
references, has described these features and
shown some good photos from this fascinat-
ing island in his well known work "'Struktur-
bóden, Solifluktion und Frostklimate der
Erde," 1944. Troll chose most of the pictures
in this work from high alpine regions, e.g.
Hohe Tauern at about 8,860 feet (2,700 m.)
and Lechtal Alps at about 7,540 feet (2,300 m.),
both in Austria, Jedigól, Ala Dag in Turkey
(north of Cyprus) at 9,840 feet (3,300 m.),
Ethiopia at 9,840-10,820 feet (3,000—3,300
m.), Mount Kenya, East Africa, at abt.
13,120-14,100 feet (4,000-4,300 m.), Drak-
bergen (the Dragon Mountains), South Afri-
ca, at 6,560—8,200 feet (2,000—2,500 m.) and
10,160—10,500 feet (3,100—3,200 m.) and Cor-
dillera Real, Bolivia, at about 15,740—16,730
feet (4,800-5,100 m.). Further, there are
striking photos from the Arctic, showing
characteristic ground patterns in West Spits-
bergen and Alaska, the Taymyr Peninsula,
Central Siberia, and others.
Washburn has chosen excellent photos of
patterned ground for his above mentioned
“Classification” from Alaska, Canada, East
Greenland, West Spitsbergen, Northern and
Middle Sweden (Dalecarlia), and Mendoza-
Argentina (Cordillera de Los Andes).
In his earlier paper on “Patterned Ground’
FrG. 12. Ground photo of mon-sorted polygons
(ice-wedge polygons) in the continuous-perma-
frost zone near Barrow, Arctic coastal plain,
Alaska. High-centered, partly cracked, polygons
(center), a great thaw lake in background. (Photo
by the author August 19, 1955.)
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Ur