Patterned ground#Stripes

{{further|Patterns in nature}}

Patterned ground can be found in a variety of forms. Typically, the type of patterned ground in a given area is related to the prevalence of larger stones in local soils and the frequency of freeze-thaw cycles.{{cite web |title=Patterned Ground |url=http://www.landforms.eu/cairngorms/patterned%20ground.htm |access-date=21 September 2016 |archive-date=29 March 2017 |archive-url=https://web.archive.org/web/20170329154935/http://www.landforms.eu/cairngorms/patterned%20ground.htm |url-status=dead }}{{cite journal | last1 = Ballantyne | first1 = C.K. |author-link=Colin Ballantyne |year = 1986 | title = Non-sorted patterned ground on mountains in the Northern Highlands of Scotland | journal = Biuletyn Peryglacjalny | volume = 30 | pages = 15–34 }}{{cite book |last=Allaby |first=Michael |title=A Dictionary of Geology and Earth Sciences |url=https://books.google.com/books?id=rjVOCgAAQBAJ&pg=PA429 |year=2013 |publisher=Oxford University Press |isbn=978-0-19-107895-8 |page=429}}{{cite web |author=Ólafur, Ingólfsson |title=Glacial Geology Photos |year=2006 |url=http://www.hi.is/~oi/index.htm |access-date=March 4, 2007}}{{cite journal |author=Kessler M.A.; Werner B.T. |title=Self-organization of sorted patterned ground |journal=Science |volume=299 |issue=5605 |pages=380–3 |date=January 2003 |pmid=12532013 |doi=10.1126/science.1077309|bibcode=2003Sci...299..380K |s2cid=27238820 }}{{cite journal |author1=Marchant, D.R. |author2=Lewis, A.R. |author3=Phillips, W.M. |author4=Moore, E.J. |author5=Souchez, R.A. |author6=Denton, G.H. |author7=Sugden, D.E. |author8=Potter Jr., N. |author9=Landis, G.P. |title=Formation of Patterned Ground and Sublimation Till over Miocene Glacier Ice in Beacon Valley, Southern Victoria Land, Antarctica |journal=Geological Society of America Bulletin |volume=114 |issue=6 |pages=718–730 |year=2002 |doi= 10.1130/0016-7606(2002)114<0718:fopgas>2.0.co;2|bibcode=2002GSAB..114..718M }}

File:Patterned ground located in the Atacama Desert (Chile).jpg]]

File:Alaska patterned ground 1973.jpg]]

Polygons can form either in permafrost areas (as ice wedges) or in areas that are affected by seasonal frost. The rocks that make up these raised stone rings typically decrease in size with depth.{{Cite journal |last=Trevor-Battye |first=Aubyn |date=1921 |title=A Theory of the Origin of Surface-Polygons in Polar Lands |url=https://www.jstor.org/stable/1781041 |journal=The Geographical Journal |volume=58 |issue=4 |pages=306–309 |doi=10.2307/1781041 |jstor=1781041 |bibcode=1921GeogJ..58..306T |issn=0016-7398|url-access=subscription }}

In the northern reaches of the Canadian Boreal forests, 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. [http://globaltwitcher.auderis.se/artspec_information.asp?thingid=44751 Black Spruce: Picea mariana, GlobalTwitcher.com, ed. N. Stromberg] {{webarchive|url=https://web.archive.org/web/20111005174426/http://globaltwitcher.auderis.se/artspec_information.asp?thingid=44751 |date=2011-10-05 }}

File:Permafrost stone-rings hg.jpgs (heaved mounds found in permafrost) have left circle-like structures on the Svalbard Archipelago.]]

Circles range in size from a few centimeters to several meters in diameter. Circles can consist of both sorted and unsorted material, and generally occur with fine sediments in the center surrounded by a circle of larger stones. Unsorted circles are similar, but rather than being surrounded by a circle of larger stones, they are bounded by a circular margin of vegetation.{{cite journal |last1=Hallet |first1=Bernard |title=Stone circles: form and soil kinematics |journal=Phil. Trans. R. Soc. Lond. A |date=2013 |volume=371 |issue=2004 |pages=20120357 |doi=10.1098/rsta.2012.0357 |pmid=24191111 |bibcode=2013RSPTA.37120357H |doi-access=free }}

Steps can be developed from circles and polygons. This form of patterned ground is generally a terrace-like feature that has a border of either larger stones or vegetation on the downslope side, and can consist of either sorted or unsorted material.

File:Periglacial stone stripes.jpg

Stripes are lines of stones, vegetation, and/or soil that typically form from transitioning steps on slopes at angles between 2° and 7°. 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.{{cite journal | last1 = King | first1 = R. B. | year = 1971 | title = Boulder polygons and stripes in the Cairngorm Mountains, Scotland | journal = Journal of Glaciology | volume = 10 | issue = 60| pages = 375–386 | doi = 10.1017/s0022143000022073 | bibcode = 1971JGlac..10..375K | doi-access = free }}{{cite journal |last1=Ballantyne |first1=Colin K. |title=The sorted stone stripes of Tingo Hill |journal=Scottish Geographical Journal |date=2001 |volume=117 |issue=4 |pages=313–324 |doi=10.1080/00369220118737131|bibcode=2001ScGJ..117..313B |s2cid=128558678 }}

It has been conjectured that periglacial stripes on Salisbury Plain in England, that happened by chance to align with the solar sunrise at mid summer and sun set at mid winter, gave rise to awe and veneration by prehistoric people that eventually culminated in the building of the Stonehenge.{{Cite web |last1=Yirka |first1=Bob |last2=Phys.org |title=New dig suggests Stonehenge was built to align with summer and winter solstice |url=https://phys.org/news/2013-09-stonehenge-built-align-summer-winter.html |access-date=2022-03-24 |website=phys.org |language=en}}

File:Phoenix mission patterned ground, Mars.jpg

{{further|Pattern formation}}

In periglacial areas and areas affected by seasonal frost, repeated freezing and thawing of groundwater forces larger stones toward the surface, as smaller stones flow and settle underneath larger stones. At the surface, areas that are rich in larger stones contain much less water than highly porous areas of finer grained sediments. These water-saturated areas of finer sediments have a much greater ability to expand and contract as freezing and thawing occur, leading to lateral forces which ultimately pile larger stones into clusters and stripes. Through time, repeated freeze-thaw cycles smooth out irregularities and odd-shaped piles to form the common polygons, circles, and stripes of patterned ground.{{cite book |first=Don J. |last=Easterbrook |title=Surface processes and landforms |url=https://books.google.com/books?id=J7oPAQAAIAAJ |year=1999 |publisher=Prentice Hall |isbn=978-0-13-860958-0 |edition=2nd |pages=418–422}}

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 {{convert|3400|m|ft|0}} to the west of Mugi Hill.{{cite book |last= Baker|first= B. H. |title= Geology of the Mount Kenya area; degree sheet 44 N.W. quarter (with coloured map)|year= 1967|publisher= Geological Survey of Kenya|location= Nairobi}} These mounds grow because of the repeated freezing and thawing of the ground drawing in more water. There are blockfields present around {{convert|4000|m|ft|0}} 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.{{cite book |last= Allan|first= Iain|title= The Mountain Club of Kenya Guide to Mount Kenya and Kilimanjaro|year= 1981|publisher= Mountain Club of Kenya|location= Nairobi|isbn= 978-9966985606}}

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.{{cite journal |author=Perkins, S. |title=Patterns from Nowhere; Natural Forces Bring Order to Untouched Ground |journal=Science News |volume=163 |issue=20 |pages=314–316 |date=17 May 2003 |url=http://www.sciencenews.org/view/feature/id/3863/title/Patterns_from_Nowhere |doi=10.2307/4014632|jstor=4014632 |url-access=subscription }}

{{div col}}

• Emergence
• Glacier
• Ice field
• Ice sheet
• Mima mounds

{{div col end}}

{{reflist|30em}}

• {{Commons category-inline}}

{{Periglacial enviroment}}

Category:Periglacial landforms

Category:Soil landforms