Geology Reference
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compressional features and irregular layering in the sand dunes refl ect the melt (“deniva-
tion”) of sand-covered snow lenses on the slip faces of many dunes. Their cold-climate
origin is deduced from the inclusion of plant, pollen, or faunal (insect) remains indicative
of cold environments and the presence of wedge structures indicative of either permafrost
or seasonal frost. Dune migration can be rapid; for example, on the Tibet Plateau a cres-
centic (barchan) dune was observed to move approximately 350 m in four years (see Figure
10.11) (Wang and French, 1995c, pp. 266-167).
Sandstone bedrock often provides a local source of sediment supply for sand dunes and
sand sheets. Also, coarse-grained glacigenic deposits (eskers, kames, glacio-fl uvial sedi-
ments) are the source for many dunes (McKenna-Neuman and Gilbert, 1986; Seppälä,
1971, 1972a; Van Vliet Lanoë et al., 1993). Late summer and winter transport is dominant,
especially on surfaces associated with proglacial discharge regimes. By contrast, on allu-
vial fl ood plains of rivers with nival discharges, sediment supplied at peak discharge in
the spring provides material for eolian transport at low discharge throughout the summer
(Fernald, 1964; Good and Bryant, 1985).
10.4. COASTAL PROCESSES AND LANDFORMS
A number of texts describe beach processes, coastal sedimentation, coastal morphology,
and the applied aspects of the world's shorelines (Bird, 2000; Komar, 1976). Several geo-
morphological summaries of cold-climate coasts are also available (John and Sugden,
1975; Viles and Spencer, 1995, pp. 254-288; Walker, 2005a, b).
The extent of coastlines currently experiencing periglacial conditions is considerable.
In the northern hemisphere, the Arctic Ocean is almost completely landlocked and exten-
sive coastlines occur in Alaska, Northern Canada, Greenland, and along the whole of the
Russian mainland from the Kola Peninsula in the west to the Chuckchi Sea in the east.
In addition, there are the various island groups such as the Canadian Arctic archipelago,
Svalbard, Franz Josef Land, Novaya Zemblya, the North Land, the New Siberian Islands,
and Wrangel Island. In Antarctica, although the majority of the coastline is composed of
ice shelves and glaciers, the Northern Victoria Land coastline and the Antarctic Peninsula
and South Shetland Islands are ice-free for several months of the year.
On the large scale, the geomorphology of cold-climate coasts is infl uenced by factors
such as geological structure, tectonic activity, and Quaternary sea-level fl uctuation. On
the medium scale, cold-climate coasts consist of a suite of depositional and erosional
landforms such as beaches, spits, inter-tidal fl ats, salt marshes, dunes, cliffs, and shore
platforms. These occur in both periglacial and non-periglacial environments and refl ect
the wind and wave regimes and the weathering and sediment-supply characteristics of the
climate. On the small scale, cold-climate coasts are dominated by the presence of ice. This
results in a number of distinctive characteristics that can be summarized under four head-
ings: the coastal-sea ice interface, the infl uence of sea ice upon wave generation, the
effects of ice upon the beach, and the infl uence of permafrost and ground ice upon coastal
development.
10.4.1. The Coastal-Sea-Ice Interface
Sea ice forms during winter from a suspension of small ice crystals (“frazil ice”) which
grow and coalesce to form a thin skin (“nila”). This evolves into a fi eld of “pancake ice,”
small ice bodies about 3 m in diameter and up to 50 cm thick, which then coalesce to form
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