Editing Silt (section)

==Human impact==
Loess underlies some of the most productive agricultural land worldwide. However, it is very susceptible to erosion.{{sfn|Assallay|Rogers|Smalley|Jefferson|1998}} The quartz particles in silt do not themselves provide nutrients, but they promote excellent [[soil structure]], and silt-sized particles of other minerals, present in smaller amounts, provide the necessary nutrients.<ref name=Chesworth1982/> Silt, deposited by annual floods along the [[Nile River]], created the rich, fertile soil that sustained the [[Ancient Egypt]]ian civilization. The closure of the [[Aswan High Dam]] has cut off this source of silt, and the fertility of the Nile delta is deteriorating.<ref>{{cite journal |last1=Stanley |first1=D. J. |last2=Warne |first2=A. G. |title=Nile Delta: Recent Geological Evolution and Human Impact |journal=Science |date=30 April 1993 |volume=260 |issue=5108 |pages=628–634 |doi=10.1126/science.260.5108.628|pmid=17812219 |bibcode=1993Sci...260..628S |s2cid=31544176 }}</ref>

Loess tends to lose strength when wetted, and this can lead to failure of building foundations.{{sfn|Assallay|Rogers|Smalley|Jefferson|1998}} The silty material has an open structure that collapses when wet.<ref>{{cite journal |last1=Rogers |first1=C.D.F. |last2=Dijkstra |first2=T.A. |last3=Smalley |first3=I.J. |title=Hydroconsolidation and subsidence of loess: Studies from China, Russia, North America and Europe |journal=Engineering Geology |date=June 1994 |volume=37 |issue=2 |pages=83–113 |doi=10.1016/0013-7952(94)90045-0}}</ref> [[Quick clay]] (a combination of very fine silt and clay-sized particles from glacial grinding) is a particular challenge for [[civil engineering]].<ref>{{cite journal |last1=Cabrera |first1=J.G. |last2=Smalley |first2=I.J. |title=Quickclays as products of glacial action: a new approach to their nature, geology, distribution and geotechnical properties |journal=Engineering Geology |date=October 1973 |volume=7 |issue=2 |pages=115–133 |doi=10.1016/0013-7952(73)90041-0|bibcode=1973EngGe...7..115C }}</ref>

The failure of the [[Teton Dam]] has been attributed to the use of loess from the Snake River floodplain in the core of the dam.<ref>{{cite journal |last1=Smalley |first1=I.J. |last2=Dijkstra |first2=T.A. |title=The Teton Dam (Idaho, U.S.A.) failure: problems with the use of loess material in earth dam structures |journal=Engineering Geology |date=October 1991 |volume=31 |issue=2 |pages=197–203 |doi=10.1016/0013-7952(91)90006-7|bibcode=1991EngGe..31..197S }}</ref> Loess lacks the necessary plasticity for use in a dam core, but its properties were poorly understood, even by the [[U.S. Bureau of Reclamation]], with its wealth of experience building [[earthen dam]]s.{{sfn|Assallay|Rogers|Smalley|Jefferson|1998}}

Silt is susceptible to [[liquefaction]] during strong earthquakes due to its lack of plasticity. This has raised concerns about the earthquake damage potential in the silty soil of the central United States in the event of a major earthquake in the [[New Madrid Seismic Zone]].<ref>{{cite journal |last1=Guo |first1=Tianqiang |last2=Prakash |first2=Shamsher |title=Liquefaction of Silts and Silt-Clay Mixtures |journal=Journal of Geotechnical and Geoenvironmental Engineering |date=August 1999 |volume=125 |issue=8 |pages=706–710 |doi=10.1061/(ASCE)1090-0241(1999)125:8(706)}}</ref><ref>{{cite journal |last1=Omermeier |first1=S.F. |last2=Jacobson |first2=R.B. |last3=Smoot |first3=J.P. |last4=Weems |first4=R.E. |last5=Gohn |first5=G.S. |last6=Monroe |first6=J.E. |last7=Powars |first7=D.S. |title=Earthquake-induced liquefaction features in the coastal setting of South Carolina and in the fluvial setting of the New Madrid seismic zone |journal=U.S. Geological Survey Professional Paper |series=Professional Paper |date=1990 |volume=1504 |doi=10.3133/pp1504|doi-access=free }}</ref>