http://www.signonsandiego.com/news/metro/20030120-9999_1m20patterns.html
UNION-TRIBUNE STAFF WRITER
January 20, 2003
Nearly five years ago, Mark Kessler found himself on the tiny, frigid
Norwegian island of Spitsbergen, looking at the ground.
All around him were strange circles made of stones, some a meter across,
some larger, bumping into one another and sprawling across the tundra.
"You walk across them, and they really are amazing to see," said
Kessler, then a University of California San Diego graduate student.
"You look down and say, 'What is this?' "
After years of observing patterns of circles, polygons, stripes and
labyrinths in arctic landscapes, Kessler and his colleagues now know.
They have developed an explanation for how the natural world can create
stunning patterns in soil and stone in some of the coldest environments
on Earth including Alaska, the Sierra, and the Rocky Mountains and
other alpine regions.
Their work appeared last week as the cover story in the journal Science.
The patterns are impossible to explain merely by the laws of physics
that govern individual stones and particles of soil.
Rather, they are the products of a natural self-organization of soil and
stones caused by freezing and thawing over decades and centuries.
"The patterns form by self-organization, and the same fundamental
processes are at work in the formation of all these different patterns,"
said Kessler, now a postdoctorate researcher at the University of
California Santa Cruz's earth sciences department.
At UCSD, Kessler and his former graduate adviser at the Scripps
Institution of Oceanography, Brad Werner, used computer models to test
their ideas about what caused the landscape patterns.
They found that the patterns resulted primarily from the interaction of
two mechanisms driven by the expansion of fine-grained soils when wet
ground freezes a process scientists call frost heave.
The expanding ground forces the lateral sorting of stones and soil, so
that soil moves toward high concentrations of soil, and stones move
toward high concentrations of stones.
It also squeezes stones into linear piles, lengthening these lines of
stones.
The relative strength of lateral sorting and squeezing, plus the slope
of the ground and the ratio of stones to soil, all determine which
pattern will emerge, Kessler and Werner found.
"One of the real mysteries to me was how you can get labyrinths or
(circles) of stones in one location and polygons in another, when the
ratio of stones to soil is the same in both places," Kessler said.
The scientists found that polygons geometric figures bounded by a
number of straight lines were formed when stones squeezed into
straight lines and angles was strong enough to counteract the effects of
lateral sorting. When lateral sorting dominated, circles of stones formed.
Which mechanism dominates depends on how compressed the soil is and the
size of the stones.
The work by Kessler and Werner reflects a change in the way scientists
who study geomorphology the study of Earth's changing topography
look for explanations for that change.
"There is nothing in the physics of a shovelful of stony mud that can
predict the emergence of an intricate pattern of interlaced,
stone-bordered polygons covering many square meters," wrote University
of Alaska researcher Daniel Mann in an essay accompanying the Science
paper.
-- There is no hope of finding the sources of free action in the lofty realms of the mind or in the depths of the brain. The idealist approach of the phenomenologists is as hopeless as the positive approach of the naturalists. To discover the sources of free action it is necessary to go outside the limits of the organism, not into the intimate sphere of the mind, but into the objective forms of social life; it is necessary to seek the sources of human consciousness and freedom in the social history of humanity. To find the soul it is necessary to lose it". A.R LuriaNate vygotsky@charter.net http://webpages.charter.net/schmolze1/
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