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Morainic Forms	Streamlined Forms	Till Composition
Push moraines Ground Moraines Ground Moraines Hill-Hole Pairs Dump Moraines Squeeze Moraines	Drumlins Flutes Rogen  Boulder trains	Composition Till Variations
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    Morainic land forms, as defined by the American Geological Institute Glossary of Geological Terms; a mound or ridge of stratified glacial drift, chiefly till, deposited by direct action of glacier ice.  Moraines are features of depositional processes which are unique in form and formation processes. To review the major forming processes see, Depositional Processes.   To classify morainic land forms, schemes of form style and processes have been used, but the vagueness of processes for certain formations create difficulties in classification. For the purposes of this page we will breakdown the features into general for
Glaitectonic Land forms
   To fully understand processes of glacitectonic land forms, once again see, Depositional Processes.

Push Moraines
Push moraines are ridges or mounds of stratified glacial drift that are generated by a glaciers fluctuation of mass balance, transgression or regression of the ice mass.  Push moraines form from the process of bulldozing the pro glacial sediments. Yearly advances

and retreats will produce a composite ridge of many crests, divided by depressions, that are aligned sub parallel with the driving ice mass.  The ridges are generally composed of multiple up thrusted sedimentary blocks.  Small composite ridges can form during a glaciers continuous regressional phase by winter accumulation advances.  The retreat of a glacial mass can be interrupted by an ice advance caused by the accumulation abnormally high amount of winter snow.  After continuous retreat a small singular crested moraine will result. If a glacier is in a phase of long term of alternating, stagnation, advance and retreat the resulting land form will be a large scale composite ridge moraine, or a continuos series or build up of push ridges.

For additional images of Push moraine formation

Hill-Hole Pairs

     Hill-hole pairs were defined by Clayton and Bluemle(84) as " a discreet hill of ice thrusted material, often slightly crumpled , situated a short distance down glacier from a depression of similar size and shape".  The cause of this feature is due to glaciotectonic processes of separating a large block of surface material and entraining it englacialy and subsequently redepositing the hill down glacier.
    Aber (1989) described the typical morphology as (a)the hill has an arcuate or concentric planform,which concave up glacier,(b) the surface of the hill is traversed by a series of transverse, sub parallel ridges and depressions, (c) the hill has an asymmetric cross profile, with the highest point and steeper slopes on the convex or down glacier side, (d) the topographic depression is approximately the same shape and area as the hill, located on the concave or up glacier side.

Ground Moraine
    Ground moraines are a low aspect ratio feature that is consist of a veneer of till (1 to 15 m) covering the underlying bed rock, and reflects the topography of that bedrock. It has a general morphology of low relief rolling features and lacking any ridge or linear features.  The emplacement process relies on the sediment amount and longevity of glacigenic dispersal.  When a ground moraine becomes thick enough to regulate its own surface topography, it is then called a cover moraine. Ground and cover moraines are great localities for boulder trains, due to the extensiveness of most cover and ground moraines.

Dump Moraine (terminal, recessional and lateral)
 

Dump moraines are emplaced by your common house hold type gravity.  Moraines are fed by sediments melting out of stagnate ice at the toe of ice. Usually they lack stratigraphy but can be bedded with glaciofluvial deposits.  To form large scale dump moraines the glacier must be at or near an equilibrium mass balance for extended amounts of time to ensure a steady amount of sediment supply.  The pictuer to the the right shows large terminal, recessional, and lateral moraines that cover the central mid-western United States (for legend to the map see picture of the push moraine.

Squeeze Moraines
    Squeeze moraines are small moranic features around one meter of height.  The ridge like forms are thought to be caused by the deformation of sediments into fractures at the basal ice interface, This is caused by the loading of ice on saturated basal sediment. The patterns sometimes are sub parallel with glacier margins, but also can form in a radial fashion thought to be the left overs of transverse crevasse fillings.  To maintain the morphology of squeeze moraines it is thought that they form when the ice flow is stagnant, other wise the flow of the overlying ice would destroy the morphology of the moraine.

Streamlined forms are formed from a variances of depositional and emplacement processes.  The most common types include drmlins and flutes.  The exact processes of formation is not well known, due to the lack of observation of ice and base interactions. We are sure that they are directly related to flow directions and have been used to trace paleo ice flow directions.  The major difference between flutes and drumlins lies in a basic equation called an Elongation ratio ,E= L/W, length divided by width. The simple equation is used due to the vast numbers of streamlined features.
Drumlins
    Drumlins are a very complex feature of glacial depsition.
 

Flutes

    Flutes are defined as elongated streamlined ridges of sediment aligned parallel to former ice flow direction formed in a sub glacial environment.  Flutes are different from drumlins in that their elongation ratio can be 2:1 and up to 60:1, such as one flute found by Clark in Canada's Northwest Territory reaching 70 km long.   The processes of formation involves the deformation of underlying of till being squeezed into cavities on the lee sides of resistant obstructions,  sediment frozen englacial at the basal-till interface and being transported and deposited in lee side cavities created by resistant objects, or a combination of both processes. A more controversial processes agues that they me be formed by instantaneous action of ice fracturing and load pressures surrounding the fracture fill the fracture by sediment deformation.  It has been debated that this may not be the case for all flutes, due to their presents on solid undeformable beds.
    Benn and Evens(98) seem to believe that there are two distinct types of flutes (a) parallel fluting and (b) tapering flutes.  Parallel flutes maintain elongation ratio for long distances along with constant cross sectional profiles. Tapering flutes are characterized lower aspect ratio and being narrower then parallel flutes. Benn and Evens(98) state that the possibilities for differences may reflect till rheology, or stress and strain responses of ice.
 Explanations for the extreme lengths of some flutes might be reflecting windows of time when ice flow was very rapid. With this statement another question arises, the sediment facies of flutes consist of unconsolidated till, which is easily erodeable, so the window of time during formation needs to be of stable directional flow conditions.  If this is the case the flute length may be directly related to ice velocity and duration under uniform directional flow.
 
 

Rogen Moraines
    Rogen moraines, also called Ribbed moraines, a good definition was given by Lundqvist (1989a) " fields of coalescent cresentric ridges
 

Boulder Trains
 
 

Composition
One of the real issues concerning the study and reconstruction of glacial systems using sedimentary facies and land forms is the composition of tills and tillites. Weathering, mass movement, and transport all affect the composition of the till through time and change its overall composition. The primary composition of the till can be linked to the erosional origin of parent material, distance from the source, and the temperature regime of the glacier (deposition process).

Sub-basal studies under modern glaciers have been studied. One study, in particular, has show that The phi distribution shows two peaks, one at the gravel size, and one at silt size material (Boulton, 1987) at the bed of an Icelandic glacier. Various parent materials, however, will weather differently. Sub-basal studies under modern glaciers have been studied. One study, in particular, has show that The phi distribution shows two peaks, one at the gravel size, and one at silt size material (Boulton, 1987) at the bed of an Icelandic glacier. Various parent materials, however, will weather differently.

Studies at the type locale for Pinedale glaciation illustrate the variability in till composition and pedogenisis through time (Hall and Shroba, 1995). Till composition was measured on the sand, silt, clay fraction of the deposit. Pinedale tills (maximum glaciation between 35 and 14 ka) had very little clay fraction in the deposit. Conversely, Bull Lake (140 ka) deposits show much greater soil development and, consequently, a greater fraction of clay (Hall and Shroba, 1995). It is also suggested that the till composition is dependent on source material. Bull Lake deposits were derived mostly from bedrock in the crystalline core of the Wind River Range. A greater fraction of this till was feldspar rich, and easily weathered to clay. The Pinedale till is suggested to be more sub-basal in origin; re-worked Bull Lake till deposited in the pre-existing glacial valley. The other processes in the interglacial period, as well as sub-basal process might be responsible for the preferential weathering and removal of clay within the diamicton later deposited as Pinedale till.
Other methods used to differentiate younger and older till sequences include pedogenisis, calcium carbonate morphology (Hall and Shorba, 1995), and cosmogenic nuclide chronology (Chadwick, et al., 1997).

Till Variations
Variation of till depth are also spatially dependent and are controlled by several variables including distance from source area. England, for instance shows progressively deeper till deposits in a southwest direction as the marine based ice center moved onto land and eroded the continental shelf and mainland (Boulton, 1996). Likewise, distance from the ice center has also been shown to affect till thickness by deposition during the retreat phase of the glaciation but this is valid only if one accepts the bed deformation genesis of till deposits proposed by Boulton (depositional process).

Locations proximal to the ice front are also areas to initially thin and retreat during deglaciation. The glacier, however, is still moving material to the ice front, especailly through sub-basal process. Likewise, the advance-phase tills are reworked because of the over-ridding ice sheets and therefore included in the retreat-phase tills. Only the most distal advance-phase tills are preserved at the surface. The advance phase till is either destroyed, or covered by the retreat-phase till (Boulton, 1996).

Burial of the advance-phase till also rises the question of the erosional capacity of a glacier. For instance, till may be 40 meters high in some places, but it is difficult to say whether the till is deposited from one glaciation, or several.  This has been discussed in the context of the advance-phase till, but it also relevant for reconstructing past glacial cycles in the Rocky Mountains, the Midwest,  and elsewhere (Boulton, 1996). The surficial morphology of a till deposit is often used to distinguish between early and late stage glacial advances, as well as to distinguish between glaciations (e.g.: Wisconsinan vs. Illinoisan).

The visible deposits, however, leave only an indicator of total work done by the glacier over geologic history. The actual work done per time unit is difficult to determine and is often complicated by other processes like mass wasting (solufluction), and fluvial erosion (Hall and Shorba, 1995) (Chadwick, et al., 1997).

The visible deposits, however, leave only an indicator of total work done by the glacier over geologic history. The actual work done per time unit is difficult to determine and is often complicated by other processes like mass wasting (solufluction), and fluvial erosion (Hall and Shorba, 1995) (Chadwick, et al., 1997). Consequently, interpretation of the sedimentary facies is highly erroneous in nature. This has caused quite a controversy about the actual erosive power per unit time, as compared to fluvial action.
 Lack of data constraints have made study of depositional landscapes difficult (Boulton, 1996). The little data available does not have the spatial resolution to make definitive theories on erosive potential and origin of till. Regional studies have been attempted in locations such as Yellowstone National Park (Shovic, 1996). Much of this study was devised from aerial photographs due to the extent of the Park. Consequently, little detailed information was developed and glacial deposition was simply labeled “glaciated highlands” which meant that the area was dominantly covered by till. A total of 52% of the Park is therefore covered in glacial till, and a remaining 15% is till covered but classified by erosional (glacial) process (Shovic, 1996). Few other studies have been done to quantify the depth and time chronology of till sequences.
 

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