Ice wedge

An ice wedge is a crack in the ground formed by a narrow or thin piece of ice that measures anywhere from 3 to 4 meters wide and extends downwards into the ground up to 10 inches. During the winter months, the water in the ground freezes and expands. Once temperatures reach -17 degrees Celsius or colder, the ice that has already formed acts like a solid and contracts to form cracks in the surface known as ice wedges. As this process continues over many years, ice wedges can grow up to the size of a swimming pool.fact|date=May 2008

Formation

The origin of ice wedges has many theories but only one has consistently been backed by the most prominent scientists: the thermal contraction theory.

Thermal contraction theory

The Thermal Contraction Theory states that during the winter months, thermal contraction cracks form only a few centimeters wide and a couple meters deep because of the extreme cold [Cite web |url=http://arctic.fws.gov/permcycl.htm |title=Ice wedges, polygons and pingos |date=2006-02-14 |accessdate=2008-05-26 |publisher=U.S. Fish & Wildlife Service - Alaska |work=Arctic National Wildlife Refuge] . Over the next few, the snow melts and the remaining water fills the cracks and the permafrost below the surface freezes it. These tiny cracks turn into permafrost. Once the summer months arrive, the permafrost expands; the fact of horizontal compression produces upturning of the frozen sediment by plastic deformation. The next winter the cold refreezes and cracks the already forming ice wedge and opens way for the eventual melting snow to fill the empty crack. The mean annual air temperature thought needed to form ice wedges is -6° to -8° C or colder.Cite web |url=http://www.britannica.com/eb/article-65736/permafrost |title=permafrost: Origins |publisher=Britannica Online Encyclopedia |accessdate=2008-05-26]

Three forms of ice wedges

There are three different forms of ice wedges: Active, Inactive and Ice Wedge Casts. All three forms are prevalent today and can be found in different parts of the world.

Active ice wedges

Active ice wedges are those that are still evolving and growing. During each year, a layer of ice will be added if cracking occurs, but cracking need not occur every year to be considered active. The zone in which most ice wedges remain active is along the permafrost zone. The amount of active ice wedges that are cracking yearly are consistently declining and becoming inactive.Cite web |url=http://www.britannica.com/eb/article-65737/ |title=permafrost: Active wedges, inactive wedges, and ice-wedge casts |publisher=Britannica Online Encyclopedia |accessdate=2008-05-26]

Inactive ice wedges

Inactive ice wedges are the wedges that are no longer cracking and growing. Throughout the winter months, the wedge does not split and therefore in the summer the no new water is added.

Ice wedge casts

In areas of past permafrost, ice wedges have melted and are no longer filled with ice. The wedge, which is now empty, is filled with sediment and dirt from the surrounding walls. These are called ice wedge casts and are used to calculate the climate of hundreds of thousands of years ago.

What ice wedges tell us about history

Ice wedges can tell a very great deal about history. After a while, when the ice wedge gets large enough and is no longer active, sediments will fill the crack left by the ice wedges. These, in turn, are called pseudomorphs and could contain important hints of the past, including animal remains.fact|date=May 2008

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • ice wedge —   when temperature fall below 15蚓, ice in soil contracts. This causes cracks to open in the ground. These may fill with water which then freezes to form an ice wedge. During interglacials, or periods of retreat, the ice melts away and the crack… …   Geography glossary

  • ice wedge — noun a vertical wedge of subterranean ice …   Wiktionary

  • ice wedge —    A massive, generally wedge shaped body with its apex pointing downward, composed of foliated or vertically banded, commonly white, ice.    NRC …   Glossary of landform and geologic terms

  • ice wedge cast —    A filling of sediment in the space formerly occupied by an ice wedge.    NRC …   Glossary of landform and geologic terms

  • ice wedge polygon —    Patterned ground in areas of ice wedges. These polygons are commonly in poorly drained areas and may be high centered or low centered.    NRC …   Glossary of landform and geologic terms

  • Ice Age — Título La edad de hielo (España) La era de hielo (Hispanoamérica) Ficha técnica Dirección Chris Wedge Carlos Saldanha Producción Lori Forte …   Wikipedia Español

  • Ice Age: Dawn of the Dinosaurs — Título Ice Age 3: el origen de los dinosaurios (España) La era de hielo 3: la era de los dinosaurios (Hispanoamérica) Ficha técnica Dirección Carlos Saldanha Mike Thurmeier Produc …   Wikipedia Español

  • Ice Age: The Meltdown — Título Ice Age 2: El deshielo (España) La era de hielo 2 (Hispanoamérica) Ficha técnica Dirección Carlos Saldanha Dirección artística Thomas Cardone …   Wikipedia Español

  • Ice Age:Continental Drift — Ice Age: Continental Drift Título La Era de Hielo 4 Ficha técnica Dirección Steve Martino Mike Thurmeier Producción Lori Forte …   Wikipedia Español

  • Ice age — Filmdaten Deutscher Titel: Ice Age Originaltitel: Ice Age Produktionsland: USA Erscheinungsjahr: 2002 Länge: 81 Minuten Originalsprache: Englisch …   Deutsch Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.