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'''Soil Liquefaction''' is the process by which saturated, unconsolidated soil or sand is converted into a suspension.  It is commonly observed in [[quicksand]], [[quick clay]], [[turbidity current]]s, and as a result of [[earthquake]] shock in unconsolidated sediments. It can be caused when flowing water reduces the [[friction]] between sand particles (as from an underground spring), or when a sudden change in pressure or repeated shock acting on water saturated or supersaturated [[sediment]]s (as in an earthquake). Although the effects of [[liquefaction]] had been observed and understood for years, it was dramatically brought to the attention of [[Engineering|engineer]]s and seismologists in 1964 during the [[Niigata, Niigata|Niigata, Japan]] and [[Alaska]] earthquakes. It was a major factor in the destruction in [[San Francisco|San Francisco's]] [[Marina District]] during the 1989 [[Loma Prieta earthquake]].

'''Soil Liquefaction''' is the process by which saturated, unconsolidated soil or sand is converted into a suspension.  It is commonly observed in [[quicksand]], [[quick clay]], [[turbidity current]]s, and as a result of [[earthquake]] shock in unconsolidated sediments. It can be caused when flowing water reduces the [[friction]] between sand particles (as from an underground spring), or when a sudden change in pressure or repeated shock acting on water saturated or supersaturated [[sediment]]s (as in an earthquake). Although the effects of '''liquefaction''' had been observed and understood for years, it was dramatically brought to the attention of [[Engineering|engineer]]s and seismologists in 1964 during the [[Niigata, Niigata|Niigata, Japan]] and [[Alaska]] earthquakes. It was a major factor in the destruction in [[San Francisco|San Francisco's]] [[Marina District]] during the 1989 [[Loma Prieta earthquake]].

== Liquefaction in earthquakes ==

== Liquefaction in earthquakes ==

The shock or repeated shock of earthquake waves can cause water-saturated soil to rearrange itself in such a way that it essentially becomes a suspension of solids in the liquid. Heavy structures on such areas can suddenly sink or shift. Buried objects can shift and relatively low density objects can ''float'' to the surface.  

The shock or repeated shock of earthquake waves can cause water-saturated soil to rearrange itself in such a way that it essentially becomes a suspension of solids in the liquid. Heavy structures on such areas can suddenly sink or shift. Buried objects can shift and relatively low density objects can ''float'' to the surface.  

:''"Often during earthquakes, fine-grained water-saturated sediments may lose their former strength and form into a thick mobile mudlike material. The process is called liquefaction. The liquefied sediment not only moves about beneath the surface but may also rise through fissures and &#8220;erupt&#8221; as mud boils and mud 'volcanoes.'"''<ref>Harold L. Levin, ''Contemporary Physical Geology'', 2nd edition (New York: Saunders College Publishing, 1986). </ref>

:''"Often during earthquakes, fine-grained water-saturated sediments may lose their former strength and form into a thick mobile mudlike material. The process is called liquefaction. The liquefied sediment not only moves about beneath the surface but may also rise through fissures and &#8220;erupt&#8221; as mud boils and mud 'volcanoes.'"''<ref>Harold L. Levin, ''Contemporary Physical Geology'', 2nd edition (New York: Saunders College Publishing, 1986).</ref>

:''"... the ground shaking reduces the strength of earth material on which heavy structures rest. Parts of many major cities, particularly port cities, have been built on naturally occurring bodies of soft, unconsolidated clay-rich sediment (such as the delta deposits of a river) or on filled areas in which large amounts of loose earth materials have been dumped to build up the land level. These water-saturated deposits often experience a change in property known as liquefaction when shaken by an earthquake. The material loses strength to the degree that it becomes a highly fluid mud, incapable of supporting buildings, which show severe tilting or collapse."''<ref>Arthur N. Strahler, Physical Geology (New York: Harper & Row, Publishers, 1981), p. 202.</ref>

:''"... the ground shaking reduces the strength of earth material on which heavy structures rest. Parts of many major cities, particularly port cities, have been built on naturally occurring bodies of soft, unconsolidated clay-rich sediment (such as the delta deposits of a river) or on filled areas in which large amounts of loose earth materials have been dumped to build up the land level. These water-saturated deposits often experience a change in property known as liquefaction when shaken by an earthquake. The material loses strength to the degree that it becomes a highly fluid mud, incapable of supporting buildings, which show severe tilting or collapse."''<ref>Arthur N. Strahler, Physical Geology (New York: Harper & Row, Publishers, 1981), p. 202.</ref>

{{Main|Quick clay}}

{{Main|Quick clay}}

[[Quick clay]], also known as '''Leda Clay''' in [[Canada]], is a unique form of highly sensitive [[clay]], with the tendency to change from a relatively stiff condition to a liquid mass when it is disturbed.  Undisturbed quick clay resembles a water-saturated [[gel]].  When a block of clay is held in the hand and struck, however, it instantly turns into a flowing ooze, a process known as spontaneous [[liquefaction]].  Quick clay behaves this way because, although it is solid, it has a very high water content, up to 80%.  The clay retains a solid structure despite the high water content, because [[surface tension]] holds water-coated flakes of clay together in a delicate structure.  When the structure is broken by a shock, it reverts to a fluid state.

[[Quick clay]], also known as '''Leda Clay''' in [[Canada]], is a unique form of highly sensitive [[clay]], with the tendency to change from a relatively stiff condition to a liquid mass when it is disturbed.  Undisturbed quick clay resembles a water-saturated [[gel]].  When a block of clay is held in the hand and struck, however, it instantly turns into a flowing ooze, a process known as spontaneous liquefaction.  Quick clay behaves this way because, although it is solid, it has a very high water content, up to 80%.  The clay retains a solid structure despite the high water content, because [[surface tension]] holds water-coated flakes of clay together in a delicate structure.  When the structure is broken by a shock, it reverts to a fluid state.

Quick clay is only found in the northern countries such as [[Russia]], [[Canada]], [[Alaska]], [[Norway]], [[Sweden]], and [[Finland]], which were glaciated during the [[Pleistocene epoch]].

Quick clay is only found in the northern countries such as [[Russia]], [[Canada]], [[Alaska]], [[Norway]], [[Sweden]], and [[Finland]], which were glaciated during the [[Pleistocene epoch]].

{{Main|Turbidity current}}

{{Main|Turbidity current}}

Submarine landslides are [[turbidity current]]s and consist of a flow of water saturated sediments flowing downslope. An example occurred 18 November 1929, when an earthquake struck the [[continental slope]] off the coast of [[Newfoundland]]. Minutes later, [[transatlantic telephone cable]]s began breaking sequentially, farther and farther downslope, away from the [[epicenter]]. Twelve cables were snapped in a total of 28 places. Exact times and locations were recorded for each break. Investigators suggested that a 60-mile-per-hour (100 km/h) submarine ''landslide'' or turbidity current of water saturated sediments swept 400 miles (600 km) down the [[continental slope]] from the earthquake&#8217;s epicenter, snapping the cables as it passed.<ref>Bruce C. Heezen and Maurice Ewing, &#8220;Turbidity Currents and Submarine Slumps, and the 1929 Grand Banks Earthquake,&#8221; American Journal of Science, Vol. 250, December 1952, pp. 849&#8211;873.</ref>

Submarine landslides are [[turbidity current]]s and consist of a flow of water saturated sediments flowing downslope. An example occurred 18 November 1929, when an earthquake struck the [[continental slope]] off the coast of [[Newfoundland]]. Minutes later, [[transatlantic telephone cable]]s began breaking sequentially, farther and farther downslope, away from the [[epicenter]]. Twelve cables were snapped in a total of 28 places. Exact times and locations were recorded for each break. Investigators suggested that a 60-mile-per-hour (100&nbsp;km/h) submarine ''landslide'' or turbidity current of water saturated sediments swept 400 miles (600&nbsp;km) down the [[continental slope]] from the earthquake&#8217;s epicenter, snapping the cables as it passed.<ref>Bruce C. Heezen and Maurice Ewing, &#8220;Turbidity Currents and Submarine Slumps, and the 1929 Grand Banks Earthquake,&#8221; American Journal of Science, Vol. 250, December 1952, pp. 849&#8211;873.</ref>

 

==External links==

==External links==

* [http://www.ce.washington.edu/~liquefaction/html/what/what1.html For a video showing liquefaction in action].

* [http://www.ce.washington.edu/~liquefaction/html/what/what1.html For a video showing liquefaction in action].

[[category:geology]]

[[Category:Geology]]