Title:
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An investigation of patterned ground
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This investigation began as a study of fossil patterned ground in East
Anglia, but was broadened in scope when it became obvious that existing
published reports of comparable active patterned ground only allowed
very limited interpretation of the patterns of East Anglia. The final
investigation included field observations on active patterns in Arctic
North America and Europe, especially the Seward Peninsula, Alaska and
Finnmark, Norway. Much of the evidence was visual and not easily
expressed in a quantitative form. A large number of diagrams and plates
are presented as an essential supplement to the inevitably subjective
description. The review of literature on patterned ground was largely
based upon the work of Washburn(1956), but information relevant to the
mechanism of origin was drawn from a wide variety or sources.
The descriptive classification suggested by Washburn was
reluctantly abandoned in the light of the field evidence, and a new
synthesis of descriptive terms is proposed. When possible existing
terms were used, taking care to avoid distorting existing definitions.
The new classification is based upon surface form, grouping and marking.
Proposed terms for form are 'equiform'(replacing the ambiguous terms
'circle', 'polygon' and 'net'), 'stripe', 'elongate'(intermediate between
stripes and equiforms) and 'step'. The grouping of patterns is
divided into 'isolate', 'contiguous' and 'grouped'(the latter for
doubtful intermediate cases). The terms 'relief', 'stone' and I
'vegetation', or combinations, are proposed for the description of
pattern marking. The terms 'sorted' and 'non sorted' are rejected
because of the contradictions arising from the dual descriptive and
genetic use of these terms, An 'other variations' category is added to
both form and marking descriptive categories to allow for occasional
occurrences not covered by the proposed terms.
Permafrost, the heat flux in ground subjected to freezing
temperatures, possible ways in which pressure in the ground is
produced by freezing, frost susceptible materials, and movements in
patterned ground are all discussed as major factors affecting patterns.
The field evidence does not differ markedly from the type of
evidence produced by previous workers, though perhaps the size and
number of excavations is notable, Air photographs were used extensive1y.
Important observations included gradations between almost all forms,
groupings and markings of patterns; clear evidence of circulatory
mover.tent in pattern sections; and e1ongated patterns apparently
parallel to lines of drainage rather than parallel to the maximum slope
Discussion of the field data includes the evaluation of evidence
on the development and perpetuation of patterned ground once the pattern
is established; direct and indirect evidence of mechanisms of movement;
evidence of actual movements; the initiation of the pattern of
patterned ground; the utility of patterned ground as a palaeoclimatic
indicator; and the rate of pattern development. An important conclusion
is that the pattern forming processes may all be incorporated into two
models for pattern development - a radial movement model and a
circulatory movement model, the former perhaps being a special
modification of the latter. Additionally each of the three main field
areas is treated independently for presentation of evidence and
deductions. The fossil patterns of East Anglia are thought to indicate
former continuous permafrost conditions. A major part of the concluding
section is entitled "Towards a more rational understanding of patterned
ground", which summarises many of the writers ideas.
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