Geology Reference
In-Depth Information
pseudo-karren exists in other regions of the world (Doerr, 1999; Ford and Williams, 1989).
It may be that similar weathering features result from different weathering processes.
4.8. CRYOBIOLOGICAL WEATHERING
It is well known that cold climates preserve things from decay. For example, the excavation
of bodies buried in permafrost in Alaska and Svalbard of individuals who died as a result
of the 1918 infl uenza epidemic has resulted in a better understanding of the genetic
code of the 1918 virus. More relevant to periglacial geomorphology is the discovery that
viable micro-organisms are present within Antarctic ice that are dated at 420 000 years
and in northern hemisphere permafrost with ages in excess of 2-3 million years (Gilichin-
sky, 2002a). In Svalbard, frozen in-situ soil and vegetation beneath a cold-based glacier
indicates microbes have survived for over 1100 years in a subglacial frozen state (Humlum
et al., 2005). All these observations indicate that one must not dismiss the potential for
biological weathering at cold temperatures.
Cold-adapted micro-organisms were fi rst described in the late nineteenth century when
bioluminescent bacteria were observed in dead fi sh preserved by low temperatures
(Gilichinsky et al., 1995). Since then, the science of cryogenics has developed, with numer-
ous applications in medicine and food technology. Surprisingly, there are relatively few
geomorphological studies that examine the role of biological activity in cold climates.
Most concern the growth of lichens, algae, or fungi in promoting rock weathering through
fl aking and exfoliation (Etienne, 2002; Fry, 1927; Hall and Otte, 1990; McCarroll and
Vines, 1995). More detailed reviews of the various micro-organisms known to exist in
permafrost are provided by D. Gilichinsky and colleagues (Gilichinsky, 1994; Gilichinsky
and Wagener, 1995; Gilichinsky et al., 1995). Although this literature is sparse, it indicates
the potential for signifi cant biological weathering at low temperatures, and further studies
are required.
Understanding the role played by bacteria and other organisms at low temperature is
important not only to soil development (see Section 4.9.1) but also to planetary science,
where the potential for life is under investigation (Gilichinsky, 2002b). The organisms that
survive in perennially-frozen conditions on Earth may possess unique mechanisms that
allow them to maintain viability for very long periods. Science needs to establish if these
mechanisms exist and, if so, what they are. Organisms that survive in permafrost may be
ancient bacteria and their analysis may reveal the nature of microbial life as it was several
million years ago. Today, the thawing of permafrost consequent upon global climate
warming (see Chapter 15) may release these organisms into the modern world, with
unpredictable consequences. This increase in microbial activity in the presence of viable
micro-organisms and radiative gases (CH
4
, CO
2
) plus the availability of organic substrates
in permafrost will further stimulate the emission of greenhouse gases. On the other hand,
increased microbial activity may also increase the ability of the tundra to function as a
sink for greenhouse gases. In summary, the complexities and uncertainties associated with
potential changes in the cryosphere indicate that cryobiological activity, in terms of both
weathering and life forms, needs further investigation.
4.9. CRYOPEDOLOGY
Soil is the end product of weathering. Therefore, any discussion of cold-climate weather-
ing must consider this topic. Cryopedology refers to the study of soils at temperatures
