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Patterned ground is the distinct and often symmetrical natural pattern of geometric shapes formed by the deformation of ground material in periglacial regions. It is typically found in remote regions of the Arctic, Antarctica, and the Outback in Australia, but is also found anywhere that freezing and thawing of soil alternate; patterned ground has also been observed in the hyper-arid Atacama Desert and on Mars. The geometric shapes and patterns associated with patterned ground are often mistaken as artistic human creations. The mechanism of the formation of patterned ground had long puzzled scientists but the introduction of computer-generated geological models in the past 20 years has allowed scientists to relate it to frost heaving, the expansion that occurs when wet, fine-grained, and porous soils freeze.
In the northern reaches of the Canadian , when bogs reach a eutrophic climax and create a sedge mat, tamarack larch and black spruce are often the early colonists within such a polygonal climax sedge mat.C. Michael Hogan. 2008. Black Spruce: Picea mariana, GlobalTwitcher.com, ed. N. Stromberg
It has been conjectured that periglacial stripes on Salisbury Plain in England, that happened by chance to align with the solar sunrise at Midsummer and sun set at Midwinter, gave rise to awe and veneration by prehistoric people that eventually culminated in the building of the Stonehenge.
Patterned ground occurs in alpine areas with freeze thaw cycles. For example, on Mount Kenya seasonal frost layer is a few centimetres (inches) below the surface in places. Patterned ground is present at to the west of Mugi Hill. These mounds grow because of the repeated freezing and thawing of the ground drawing in more water. There are blockfields present around where the ground has cracked to form hexagons. Solifluction occurs when the night temperatures freeze the soil before it thaws again in the morning. This daily expansion and contraction of the soil prevents the establishment of vegetation.
Frost also sorts the sediments in the ground. Once the mantle has been weathered, finer particles tend to migrate away from the freezing front, and larger particles migrate through the action of gravity. Patterned ground forms mostly within the active layer of permafrost.
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