Frozen ground - Revision history

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	<onlyinclude>'''Frozen ground''' occurs when ground water freezes due to the temperature of the ground being below 0[[celsius\|°C]].<ref name=RE1>"All About Frozen Ground \| All About Frozen Ground \| National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: http://nsidc.org/cryosphere/frozenground/index.html. [Accessed: 05- Jun- 2016].</ref> The ground freezes when the water freezes between rocks, soil, and pebbles. In this context, this frozen [[water]] is called pore [[ice]].<ref name=RE2>"All About Frozen Ground \| How Does Frozen Ground Form? \| National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: https://nsidc.org/cryosphere/frozenground/how_fg_forms.html. [Accessed: 06- Jun- 2016].</ref~~></onlyinclude~~> The ground freezes when the water in the ground becomes ice and the ground thaws when the pore ice melts. When the ground thaws, it's not melting; thawed soil is still solid.		<onlyinclude>'''Frozen ground''' occurs when ground water freezes due to the temperature of the ground being below 0[[celsius\|°C]].<ref name=RE1>"All About Frozen Ground \| All About Frozen Ground \| National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: http://nsidc.org/cryosphere/frozenground/index.html. [Accessed: 05- Jun- 2016].</ref> The ground freezes when the water freezes between rocks, soil, and pebbles. In this context, this frozen [[water]] is called ''pore [[ice]]''.</onlyinclude><ref name=RE2>"All About Frozen Ground \| How Does Frozen Ground Form? \| National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: https://nsidc.org/cryosphere/frozenground/how_fg_forms.html. [Accessed: 06- Jun- 2016].</ref> The ground freezes when the water in the ground becomes ice and the ground thaws when the pore ice melts. When the ground thaws, it is not "melting"; thawed soil is still solid.

	==Freezing Processes==		==Freezing Processes==
	In the Northern Hemisphere, more than half of the entire land surface freezes and thaws every year, which is called seasonally frozen ground. A quarter of the land in the Northern Hemisphere has an underground layer that stays frozen all year long. Ground that stays frozen for at least two years in a row is called [[permafrost]].<ref name=RE1/> The freeze and thaw cycle of the ground has the power to split fence posts, crack rock and gravel causing roads to become bumpy. In certain areas, entire towns are built on frozen ground, which stays frozen the entire year; this means there are dependences on the ground staying frozen.		In the Northern Hemisphere, more than half of the entire land surface freezes and thaws every year, which is called '''seasonally frozen ground'''. A quarter of the land in the Northern Hemisphere has an underground layer that stays frozen all year long. Ground that stays frozen for at least two years in a row is called [[permafrost]].<ref name=RE1/> The freeze and thaw cycle of the ground has the power to split fence posts, crack rock and gravel causing roads to become bumpy. In Figure 1, trees are leaning because of the thawing of frozen ground. In certain areas, entire towns are built on frozen ground, which stays frozen the entire year; this means there are dependences on the ground staying frozen.
	[[File:20070801_forest.jpg\|thumb\|400px\|right\|Figure 1. Drunken trees caused by the impact of frozen ground.<ref>wikicommons. (July 22, 2016). ‘’Drunken Trees’’ [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/7/7f/20070801_forest.jpg</ref>]]		[[File:20070801_forest.jpg\|thumb\|400px\|right\|Figure 1. Drunken trees caused by the impact of frozen ground.<ref>wikicommons. (July 22, 2016). ‘’Drunken Trees’’ [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/7/7f/20070801_forest.jpg</ref>]]

	When ground water freezes becoming ice, it expands ~~pushing~~ soil in the ground causing it to swell. ~~Often times, in~~ frigid regions, a layer of pure ice~~, which~~ is formed by attracting water~~, forms under the soil~~. This process causes more water to be attracted and thus more ice is formed. The segregated ice layer can be several [[meter]]s thick. It forms when pore ice attracts water, which freezes and attracts even more water as the cycle continues. This effect is called cryosuction.<ref name=RE2/> Cryosuction makes the frozen layer grow, and the growing layer expands the soil even more. Cryosuction can make permanently frozen ground expand by 50%.<ref name=RE2/>		When ground water freezes (becoming ice) it expands and pushes soil in the ground, causing it to swell. In frigid (very cold) regions, a layer of pure ice under the soil is often formed by attracting water. This process causes more water to be attracted and thus more ice is formed. The segregated ice layer can be several [[meter]]s thick. It forms when pore ice attracts water, which freezes and attracts even more water as the cycle continues in a [[Feedback cycle\|positive feedback loop]]. This effect is called ''cryosuction''.<ref name=RE2/> Cryosuction makes the frozen layer grow, and the growing layer expands the soil even more. Cryosuction can make permanently frozen ground expand by 50%.<ref name=RE2/>
	==Ground Temperature Variations==		==Ground Temperature Variations==
	The [[land surface temperature\|ground temperature]] is often different from the [[land surface air temperature\|temperature]] of the air above it. Layers deep within the ground may be [[geothermal gradient\| colder or warmer than layers near the surface]] of the ground<ref name=RE2/>. The top layer of the ground reacts to conditions on the surface, but the lower layers respond more slowly to changes at the surface. In summer, the ground surface absorbs heat and becomes warmer than the ambient air. However, the temperature a meter below the surface is usually much cooler than the air. In contrast, during the winter season, the ground surface cools, but the layer underground usually stays warmer than the surface. The upper layer of ground traps heat, preventing it from moving between the cold air and the deeper layers of the ground ultimately displaying that the earth insulates itself. The type of soil also impacts how the ground stores heat. Loose soils such as sand have more pore space for water retention.<ref name=RE2/> Looser soils have larger particles, so ice forms more easily. Dense soils have smaller particles and do not have as much space for water.<ref name=RE2/> This means that clay does not freeze as easily as sand.		The [[land surface temperature\|ground temperature]] is often different from the [[land surface air temperature\|temperature]] of the air above it. Layers deep within the ground may be [[geothermal gradient\|colder or warmer than layers near the surface]] of the ground.<ref name=RE2/> The top layer of the ground reacts to conditions on the surface, but the lower layers respond more slowly to changes at the surface.

			* In ''summer'', the ground surface absorbs heat and becomes warmer than the ambient air. However, the temperature a meter below the surface is usually much cooler than the air.
			* In contrast, during the ''winter'' season, the ground surface cools, but the layer underground usually stays warmer than the surface. The upper layer of ground traps heat, preventing it from moving between the cold air and the deeper layers of the ground ultimately displaying that the earth insulates itself.

			The type of soil also impacts how the ground stores heat. Loose soils such as sand have more pore space for water retention.<ref name="RE2" /> Looser soils have larger particles, so ice forms more easily. Dense soils have smaller particles and do not have as much space for water.<ref name="RE2" /> This means that clay does not freeze as easily as sand.
	==Natural Heat Sources==		==Natural Heat Sources==
	Changes in [[solar radiation]] also affects frozen ground. Since the ground receives no heat from the [[Sun]] at night, it releases stored heat ~~during~~ the day. The ground may freeze overnight and then thaw the next day with the Sun's heat. In some places, the ground only absorbs enough heat in the summer to thaw the top layer of the ground.<ref name=RE3>"What Affects Frozen Ground? \| National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: https://nsidc.org/cryosphere/frozenground/what_affects_fg.html. [Accessed: 05- Jun- 2016].</ref> This top layer of ground is called the active layer~~. The~~ layer underneath stays frozen. [[Snow]] and ice are light colored and reflect more heat away.<ref name=RE2/> [[Ocean]] water and bare ground absorb more heat and reflect less. The amount of light that's reflected is called the [[albedo]]. This transfer of heat between the ground and the air is called the surface energy flux.<ref name=RE2/> Heat is also coming from the [[Cross section of the Earth\|Earth's core]] which is very hot, ~~and its~~ heat moves towards the surface. This movement of heat to the surface is called the geothermal heat flux. The geothermal heat flux can stop the ground from freezing. However, even in very cold areas, the ground can only freeze so far before the geothermal heat flux stops it.<ref name=RE2/> A thick layer of snow ~~acts~~ like a blanket so that heat does not leave the ground.<ref name=RE3/> Only a thin layer of ground will freeze under a thick layer of snow. Light-colored soils freeze sooner and stay frozen longer than dark soils because these surfaces reflect sunlight, keeping the ground cooler.<ref name=RE3/> [[Peat]] is soil that forms when dead plants do not decompose all the way.<ref name=RE3/> Peat is found in marshy areas that form when the active layer thaws. The ground beneath the peat is usually colder than ground not covered by a peat layer. In the winter, peat freezes and allows heat to leave the ground. Because the heat escapes, more frozen ground and permafrost form.<ref name=RE3/>		Changes in [[solar radiation]] also affects frozen ground. Since the ground receives no heat from the [[Sun]] at night, it releases stored heat from the day. The ground may freeze overnight and then thaw the next day with the Sun's heat. In some places, the ground only absorbs enough heat in the summer to thaw the top layer of the ground.<ref name=RE3>"What Affects Frozen Ground? \| National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: https://nsidc.org/cryosphere/frozenground/what_affects_fg.html. [Accessed: 05- Jun- 2016].</ref> This top layer of ground is called the ''active layer'', the layer underneath stays frozen.

			[[Snow]] and ice are light colored and reflect more heat away.<ref name="RE2" /> [[Ocean]] water and bare ground absorb more heat and reflect less. The amount of light that's reflected is called the [[albedo]]. This transfer of heat between the ground and the air is called the '''surface energy flux'''.<ref name="RE2" /> Heat is also coming from the [[Cross section of the Earth\|Earth's core]], which is very hot, this heat moves towards the surface. This movement of heat to the surface is called the '''geothermal heat flux'''. The geothermal heat flux can stop the ground from freezing. However, even in very cold areas, the ground can only freeze so far before the geothermal heat flux stops it.<ref name="RE2" />

			A thick layer of snow can act like a blanket so that heat does not leave the ground.<ref name="RE3" /> Only a thin layer of ground will freeze under a thick layer of snow. Light-colored soils freeze sooner and stay frozen longer than dark soils because these surfaces reflect sunlight, keeping the ground cooler.<ref name="RE3" /> [[Peat]] is soil that forms when dead plants do not decompose all the way.<ref name="RE3" /> Peat is found in marshy areas that form when the active layer thaws. The ground beneath the peat is usually colder than ground not covered by a peat layer. In the winter, peat freezes and allows heat to leave the ground. Because the heat escapes, more frozen ground and permafrost form.<ref name="RE3" />
	==Altitude Effects==		==Altitude Effects==
	Places with higher altitudes are colder because Earth's atmosphere is thinner ~~there~~ therefore ~~not trapping~~ as much heat as in lower elevations or thicker areas of the atmosphere. Earth's atmosphere is like a blanket ~~as it~~ holds heat near Earth's surface. For every 100 meters increase in altitude, the average air temperature drop is 0.6°C.<ref name=RE3/> This is called the [[lapse rate]].		Places with higher altitudes are colder because Earth's atmosphere is thinner, therefore can't trap as much heat as lower elevations (or thicker areas of the atmosphere) do. Earth's atmosphere is like a blanket that holds heat near Earth's surface. For every 100 meters increase in altitude, the average air temperature drop is 0.6°C.<ref name=RE3/> This is called the [[lapse rate]].

			When frozen ground thaws, the environment changes dramatically. For example, thawing permafrost on mountain slopes can lead to [[landslide]]s.<ref name=RE4>"How Does Frozen Ground Affect Land? \| National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: https://nsidc.org/cryosphere/frozenground/how_fg_affects_land.html. [Accessed: 06- Jun- 2016].</ref> When permafrost thaws on level ground, the ground buckles, trees growing nearby can be at risk as their roots become so weak that trees tilt and fall over. These trees are sometimes called a drunken forest, see Figure 1 above.<ref name=RE4/>

			== For Further Reading ==
			For more information on permafrost and frozen ground please see [http://www.pmel.noaa.gov/arctic-zone/detect/land-permafrost.shtml NOAA] or the [https://nsidc.org/learn/parts-cryosphere/frozen-ground-permafrost NDIC].

	~~When frozen ground thaws,~~ the ~~environment changes dramatically. For example, thawing permafrost on mountain slopes can lead to~~ [[~~landslide~~]]~~s.<ref name=RE4>"How Does Frozen Ground Affect Land? \| National Snow and Ice Data Center", National Snow and Ice Data Center, 2016.~~ [~~Online]. Available: https://nsidc.org/cryosphere/frozenground/how_fg_affects_land.html.~~ [~~Accessed~~: ~~06- Jun- 2016~~].</ref> When permafrost thaws on level ground, the ground buckles, trees growing nearby can be at risk as their roots become so weak that trees tilt and fall over. Trees growing nearby can be at risk. Sometimes, their roots become so weak that trees tilt and fall over. These trees are sometimes called a drunken forest.<ref name=RE4/>		* [[Geothermal gradient]]
			* [[Sunlight]]
			* [[Cross section of the Earth]]
			* [[Permafrost]]
			* Or explore a [[Special:Random\|random page]]

	For more information on permafrost and frozen ground please see [http://www.pmel.noaa.gov/arctic-zone/detect/land-permafrost.shtml NOAA] or the [http://nsidc.org/cryosphere/frozenground/index.html NDIC].
	==References==		==References==
	{{reflist}}		{{reflist}}
			[[Category: Uploaded]]

Jmdonev: 1 revision imported: From the summer

2016-09-17T22:29:41Z

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Jmdonev at 22:51, 3 August 2016

2016-08-03T22:51:15Z

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[[Category:Done 2016-04-30]]
<onlyinclude>'''Frozen ground''' occurs when ground water freezes due to the temperature of the ground being below 0[[celsius|°C]].<ref name=RE1>"All About Frozen Ground | All About Frozen Ground | National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: http://nsidc.org/cryosphere/frozenground/index.html. [Accessed: 05- Jun- 2016].</ref> The ground freezes when the water freezes between rocks, soil, and pebbles. In this context, this frozen [[water]] is called pore [[ice]].<ref name=RE2>"All About Frozen Ground | How Does Frozen Ground Form? | National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: https://nsidc.org/cryosphere/frozenground/how_fg_forms.html. [Accessed: 06- Jun- 2016].</ref></onlyinclude> The ground freezes when the water in the ground becomes ice and the ground thaws when the pore ice melts. When the ground thaws, it's not melting; thawed soil is still solid.
==Freezing Processes==
In the Northern Hemisphere, more than half of the entire land surface freezes and thaws every year, which is called seasonally frozen ground. A quarter of the land in the Northern Hemisphere has an underground layer that stays frozen all year long. Ground that stays frozen for at least two years in a row is called [[permafrost]].<ref name=RE1/> The freeze and thaw cycle of the ground has the power to split fence posts, crack rock and gravel causing roads to become bumpy. In certain areas, entire towns are built on frozen ground, which stays frozen the entire year; this means there are dependences on the ground staying frozen.
[[File:20070801_forest.jpg|thumb|400px|right|Figure 1. Drunken trees caused by the impact of frozen ground.<ref>wikicommons. (July 22, 2016). ‘’Drunken Trees’’ [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/7/7f/20070801_forest.jpg</ref>]]

When ground water freezes becoming ice, it expands pushing soil in the ground causing it to swell. Often times, in frigid regions, a layer of pure ice, which is formed by attracting water, forms under the soil. This process causes more water to be attracted and thus more ice is formed. The segregated ice layer can be several [[meter]]s thick. It forms when pore ice attracts water, which freezes and attracts even more water as the cycle continues. This effect is called cryosuction.<ref name=RE2/> Cryosuction makes the frozen layer grow, and the growing layer expands the soil even more. Cryosuction can make permanently frozen ground expand by 50%.<ref name=RE2/>
==Ground Temperature Variations==
The [[land surface temperature|ground temperature]] is often different from the [[land surface air temperature|temperature]] of the air above it. Layers deep within the ground may be [[geothermal gradient| colder or warmer than layers near the surface]] of the ground<ref name=RE2/>. The top layer of the ground reacts to conditions on the surface, but the lower layers respond more slowly to changes at the surface. In summer, the ground surface absorbs heat and becomes warmer than the ambient air. However, the temperature a meter below the surface is usually much cooler than the air. In contrast, during the winter season, the ground surface cools, but the layer underground usually stays warmer than the surface. The upper layer of ground traps heat, preventing it from moving between the cold air and the deeper layers of the ground ultimately displaying that the earth insulates itself. The type of soil also impacts how the ground stores heat. Loose soils such as sand have more pore space for water retention.<ref name=RE2/> Looser soils have larger particles, so ice forms more easily. Dense soils have smaller particles and do not have as much space for water.<ref name=RE2/> This means that clay does not freeze as easily as sand.
==Natural Heat Sources==
Changes in [[solar radiation]] also affects frozen ground. Since the ground receives no heat from the [[Sun]] at night, it releases stored heat during the day. The ground may freeze overnight and then thaw the next day with the Sun's heat. In some places, the ground only absorbs enough heat in the summer to thaw the top layer of the ground.<ref name=RE3>"What Affects Frozen Ground? | National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: https://nsidc.org/cryosphere/frozenground/what_affects_fg.html. [Accessed: 05- Jun- 2016].</ref> This top layer of ground is called the active layer. The layer underneath stays frozen. [[Snow]] and ice are light colored and reflect more heat away.<ref name=RE2/> [[Ocean]] water and bare ground absorb more heat and reflect less. The amount of light that's reflected is called the [[albedo]]. This transfer of heat between the ground and the air is called the surface energy flux.<ref name=RE2/> Heat is also coming from the [[Cross section of the Earth|Earth's core]] which is very hot, and its heat moves towards the surface. This movement of heat to the surface is called the geothermal heat flux. The geothermal heat flux can stop the ground from freezing. However, even in very cold areas, the ground can only freeze so far before the geothermal heat flux stops it.<ref name=RE2/> A thick layer of snow acts like a blanket so that heat does not leave the ground.<ref name=RE3/> Only a thin layer of ground will freeze under a thick layer of snow. Light-colored soils freeze sooner and stay frozen longer than dark soils because these surfaces reflect sunlight, keeping the ground cooler.<ref name=RE3/> [[Peat]] is soil that forms when dead plants do not decompose all the way.<ref name=RE3/> Peat is found in marshy areas that form when the active layer thaws. The ground beneath the peat is usually colder than ground not covered by a peat layer. In the winter, peat freezes and allows heat to leave the ground. Because the heat escapes, more frozen ground and permafrost form.<ref name=RE3/>
==Altitude Effects==
Places with higher altitudes are colder because Earth's atmosphere is thinner there therefore not trapping as much heat as in lower elevations or thicker areas of the atmosphere. Earth's atmosphere is like a blanket as it holds heat near Earth's surface. For every 100 meters increase in altitude, the average air temperature drop is 0.6°C.<ref name=RE3/> This is called the [[lapse rate]].

When frozen ground thaws, the environment changes dramatically. For example, thawing permafrost on mountain slopes can lead to [[landslide]]s.<ref name=RE4>"How Does Frozen Ground Affect Land? | National Snow and Ice Data Center", National Snow and Ice Data Center, 2016. [Online]. Available: https://nsidc.org/cryosphere/frozenground/how_fg_affects_land.html. [Accessed: 06- Jun- 2016].</ref> When permafrost thaws on level ground, the ground buckles, trees growing nearby can be at risk as their roots become so weak that trees tilt and fall over. Trees growing nearby can be at risk. Sometimes, their roots become so weak that trees tilt and fall over. These trees are sometimes called a drunken forest.<ref name=RE4/>

For more information on permafrost and frozen ground please see [http://www.pmel.noaa.gov/arctic-zone/detect/land-permafrost.shtml NOAA] or the [http://nsidc.org/cryosphere/frozenground/index.html NDIC].
==References==
{{reflist}}