various forms of morainic deposits

Moraine is an accumulation of the heterogeneous rubbly material including angular blocks of rocks,pebbles,boulders,clay that has been transported and deposited by a glacier or ice sheet.they are classified on the basis of the mode of their formation i.e.,supragalacial,englacial and subglacial environments.

the different types of moraines are:-

A)rogen or ribbed moraines:-

they are found transverse to the main direction.The ridges exhibit slight down-ice pattern.there are 3 main hypothesis of it's formation:-

1)Subglacial;

2)Stagnant ice;

3)subglacial;

4)subglacial meltwater floods;

5)Crevasses fillings;

6)Marginal moraine formation.

It exhibit wide range of sdiment types and structures  although stratified sediemnts are often the dominant type.they typically occur beyond  centres of glaciation.they occur at the distances of >200 Km. from ice sheet and rarely within the 200 Km. - 300 Km. of ice margins.

               there are several morainic forms that are initiated under active ice conditions but appear to attain their final form and morphological character under passive ice disintegration.they are:-

1)Pulju moraines:-It consists of an area of the chaotic ridges which are winding and hummocky.Their origin is problematic.It is probably formed due to squeezing up of the sediments into the crevasses or due to the general ice disintegration during the deglaciation due to layeral pressure induced ridging,both under the passive ice conditions.The preferentially occur within the 200 Km. of an ice divide.

2)Veiki moraines:-They appear like a near circular plateau surrounded by a single or double rim/ridge.Mechanisms of it's formation are subdivided into:-a)Subglacial origins under passive/active ice;

b)Supraglacial origins.

3)Hummocky moraines:-

They are chaotic steep-sided piles of the dominantly subglacial debris that lack a coherent directional pattern and are often associated with marginal areas of ice masses.It has an active origin.However,in  Rannoch Moor ,Scotland,a subglacial active ice origin seemed appropriate.

4)Blatnik maoraines:-

During the one of the bed form transition styles where drumlins become incomplete with their down-ice,lee ends truncated or eplaced by a concave end.These incomplete drumlins begin to become alligned side by side forming ridges transverse  to the main ice direction.This transition zone separately termed as blatnik moraines.

5)De Geer moraines/cross valley moraines/washboard moraines:-

It is a nonbed form subglacial landform.these ridges are transverse to the main ice direction slightly with arcuate down ice plan form with an asymmetric cross-section.The distal slope tends to be the steepest.In many cases they are seasonal in form.It is suggested the debris  during it's formation was squeezed up into transverse  basal crevasses.They merely reflect temporary positions of the nearby dynamic grounding-line and hence,has a limited geochronological significance.Although formed of an array of sediments,they have stratified sediment deposits.

6)End moraines:-

They are ridges accumulating along and at margins of the glaciers.It's a ice marginal glacial form.They may partially reflect bedrock topography,earlier glacial event or multiple depositional episodes.

a)Superposed end moraines:-Those composed of the deposits from the >=2 glacial advances.

b)Rock-cored end moraines:-Those occurring  over bedrock highs.

c)Palimpsest end moraines:-Those that are buried by relatively thin drift ice caps are commonly arcuate in outline,while some are short or composed of discontinuous ridges.Many end moraines are composed of diamiction and sorted sediment  that originated in supraglacial environment though subglacial till may also occur commonly followed by debris flow deposit and sorted fluvial and lacustrine sediments.

Push moraines are end moraines of the glaciolacustrine origin composed primarily of the large thrust masses of the sediment and bedrock,often imbricated,that have been derived from beneath the glacier.Example:-Pleistocene push moraines of the Dammer Berge,Germany.

7)Ramp type sub-lacustrine moraines:-

They are formed on the morainal banks and by the process of the subglacial lodgement.

8)Frontal dump moraines:-

They are formed from meltout at the terminus and dumping of the supraglacial debis during calving process.

9)Terminal moraines:-

A linear ridge of the glacial debris marking the maximum limit of an ice sheet or the glacier.It's proximal slope is steeper than it's distal slope since the former represents ice constant  slope.