Editing Till (section)

==Types of till==
There are various types of classifying tills:
* Primary deposits – Laid down directly by glacier action.<ref name=":1" />
* Secondary deposits –  Reworked by fluvial transport, erosion, etc.<ref name=":1" />

Traditionally (e.g. [[Aleksis Dreimanis|Dreimanis]], 1988<ref name=":1">Dreimanis, A., [https://scholar.google.com/scholar_url?url=ftp://ww4.dnr.wa.gov/geology/polenz/refs/Dreimanis_1988_till.pdf&hl=en&sa=T&oi=gsb-ggp&ct=res&cd=0&d=11099027640699497667&ei=OMZ9YuaKOqKP6rQPv9mc6Ac&scisig=AAGBfm2YI3t7eayr8mqnXbgOwCEAxz3hyg 1988. Tills: Their genetic terminology and classification], pp. 17–83. In R. P. Goldthwait and C. L. Matsch, éd., Genetic classification of glacigenic deposits. A. A. Balkema, Rotterdam</ref>) a further set of divisions has been made to primary deposits, based upon the method of deposition. Van der Meer et al. 2003<ref>Meer, J.J.M. van der, Menzies, J. and Rose, J. 2003. Subglacial till: The deforming glacier bed. Quaternary Science Reviews 22, pp. 1659–85.</ref> have suggested that these till classifications are outdated and should instead be replaced with only one classification, that of deformation till.  The reasons behind this are largely down to the difficulties in accurately classifying different tills, which are often based on inferences of the physical setting of the till rather than detailed analysis of the till fabric or particle size.

===Subglacial till===
====Lodgement till====

Subglacial lodgement tills are deposits beneath the glacier that are forced, or "lodged" into the bed below. As glaciers advance or retreat, the clasts that are deposited by the ice may have a lower velocity than the ice itself. When the friction between the clast and the bed exceeds the forces of the ice flowing above and around it, the clast will cease to move, and it will become a lodgement till.

====Meltout till====

Subglacial meltout tills are tills that are deposited via the melting of the ice lobe. Clasts are transported to the base of the glacier over time, and as basal melting continues, they are slowly deposited below the glacier. Since the rate of deposition is controlled by the rate of basal melting, it is worth considering the factors that contribute to melting. These can be the geothermal heat flux, frictional heat generated by sliding, ice thickness, and ice-surface temperature gradients.

====Deformation till====

Subglacial deformation tills refer to the homogenization of glacial sediments that occur when the stresses and shear forces from the moving glacier rework the topography of the bed. These contain preglacial sediments (non glacial or earlier glacial sediments), which have been run over and thus deformed by meltout processes or lodgement. The constant reworking of these deposited tills leads to a highly homogenized till.<ref name=":0" />

===Supraglacial till===

====Meltout till====

Supraglacial meltout tills are similar to subglacial meltout tills. Rather than being the product of basal melting, however, supraglacial meltout tills are imposed on top of the glacier. These consist of clasts and debris that become exposed due to melting via solar radiation. These debris are either just debris that have a high relative position on the glacier, or clasts that have been transported up from the base of the glacier. Debris accumulation has a feedback-loop relationship with melting. Initially, the darker colored debris absorb more heat and thus accelerate the melting process. After a significant amount of melting has occurred, the thickness of the till insulates the ice sheet and slows the melting process. Supraglacial meltout tills typically end up forming moraines.

====Flow till====

Supraglacial flow tills refer to tills that are subject to a dense concentration of clasts and debris from meltout. These debris localities are then subsequently affected by [[ablation]]. Due to their unstable nature, they are subject to downslope flow, and thus named "flow till." Properties of flow tills vary, and can depend on factors such as water content, surface gradient, and debris characteristics. Generally, flow tills with a higher water content behave more fluidly, and thus are more susceptible to flow. There are three main types of flows, which are listed below.
*Mobile flows: Thin, fluid, and rapid flows that significantly contribute to erosional processes. These cause strong clast orientation in the direction of flow.
*Semi-plastic: Thick, slow moving "tongues" of debris. These are also erosive, and clast sorting is more organized than in mobile flows.
*Creep: Very slow movement of debris, downslope in direction. Flow rate is slow enough not to be seen on relatively short timescales, as observed by humans. Particle orientation is often random and not associated with the direction of flow.<ref name=":0">{{Cite book|last=Bennett|first=Mathew|title=Glacial Geology: Ice Sheets and Landforms|publisher=Wiley-Blackwell|year=2009|isbn=978-0-470-51690-4}}</ref>