First 197 words of the document:
Polygons can form either in
permafrost areas or in areas
that are affected by seasonal
frost. The rocks that make up
these raised stone rings typically
decrease in size with depth.
Stripes are lines of stones,
vegetation, and/or soil that typically form
from transitioning steps on slopes at angles
between 2º and 7º. Stripes can consist of
either sorted or unsorted material. Sorted
stripes are lines of larger stones separated
by areas of smaller stones, fine sediment, or
vegetation. Unsorted stripes typically
consist of lines of vegetation or soil that are
separated by bare ground.
The water in the ground freezes and expands.
Then, as the temperature falls further, (below
17°C), the soil and frozen ice acts as a
solid and contracts as it gets colder, forming
cracks. The cracks form in the shape of
large polygons, sometimes as large as a
swimming pool. In the spring the
melt-water flows into these cracks,
re-freezing almost immediately until it
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when the ice melted, the water on the surface of the land carved wide valleys.
Today these valleys don't have any rivers because it sinks through into the
limestone and flows underground in caverns.…read more