Permafrost

can lead to a global ecological catastrophe with problems of dangerous engineering-cryogenic
processes activation, frozen nowadays pollutants are to melt and join the food chain. The sea
transgression is expected as so as glacial and permafrost disasters occur also in not urbanized
areas but they are lesser-observed and not contacting directly with society. Degradation and
regeneration of permafrost at various sites show the strict localization of these processes.
Permafrost destabilization often leads to negative for settlers results but the process is natural at
all. At urbanized sites of cryolithozone the human risk occurs. Social interest is to save the
environment directly surrounding it. That is why human unobjectively enlarges the local
problems to the scale of Earth. The only problem then is controlling the permafrost conditions
to use it.
Key words: Negative consequences, permafrost degradation
Late-pleistocene Permafrost Events in Southern
New Jersey, Eastern U.S.A.
Hugh French 1 , Mark Demitroff 2 and Steve Forman 3
(1.Departments of Geography and Earth Sciences, University of Ottawa, Ontario, Canada
2.Department of Geography, University of Delaware, Newark, Delaware, USA
3. Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, Illinois, USA)
Abstract: Recent field studies in the Pine Barrens of Southern New Jersey have documented
the occurrence of relict sand wedges and numerous deformational structures. This area lay
beyond the maximum southern limits of the Late-Pleistocene ice sheets in North America. The
wedge structures are the result of thermal-contraction cracking and indicate the previous
existence of permafrost. Modern analogs suggest mean annual air temperatures of at least
-3.0ºC to -4.0ºC for their formation. Wedge infill material has been dated by
optically-stimulated luminescence (OSL). The dates obtained suggest at least two, probably
three, periods of thermal-contraction cracking during the last 150,000 to 200,000 years.
The deformational structures are interpreted to reflect thermokarst activity when
permafrost degraded, icy layers melted, and density-controlled mass displacements occurred in
water-saturated sediments. The most common deformations extend for several tens of metres in
horizontal extent and affect sediments at depths as great as 3-4 m below the ground surface. For
this reason, they cannot be interpreted as either cryoturbation within the active layer or the
result of deep seasonal frost. Others take the form of deformed wedge-like structures, and
bulbous ‘sediment pots’ or kettles. These structures are thought to have formed when gullying
and fluvio-thermal erosion operated preferentially along fissures and sand wedges as permafrost
degraded. Other non-diastrophic structures are associated with layers of bog ironstone, 1-2 m
thick. These are broken and disrupted. They are thought to have ‘foundered’, or sank, in
water-saturated sediments that had lost inter-granular cohesion when icy beds melted.
A number of OSL ages now permit construction of a tentative permafrost chronology for
Southern New Jersey. We attach most significance to the age determinations made upon the
coarse-grained (150-250 µm) quartz fraction.
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