Melt water is hugely important in allowing glaciers to move by basal slippage within Temperate or warm based glaciers.  It is also responsible for a range of other landforms, which are collectively known as fluvioglacial landforms (recall – fluvial is just a posh Geography word for rivers).  Melt water can create landforms through both erosion and deposition, and the environment is highly dynamic and in constant flux.

Melt water moves in many ways through a glacier, water can move on the glaciers surface (supraglacial channels), within the ice (englacial channels) and under the ice (subglacially).

Water that flows on the surface and then enters and englacial channel does so through a MOULIN.

The key point here is that melt water streams are highly dynamic and highly VARIABLE – both in terms of their discharge and sediment load. Discharge can vary wildly over time;

In summer discharges will be very high, as melt water arrives from many melt water streams from all over the glacier.  In winter, melt water discharge may even stop, as temperature may never rise above the pressure melting point.  Discharges also vary on a DAILY basis, with greatest discharges coinciding with the greatest daily temperatures (albeit with a LAGTIME to allow the water to reach melt water channels. Extreme floods or discharge events are known as Jökulhlaup events.

The processes associated with melt water channels are essentially river processes such as;

Erosion Processes
Hydraulic Action - where the sheer force of the water erodes the stones, bed and banks of the river

Corrasion - where stones in transport are thrown into the bed and the banks eroding them

Corrosion - where weak acids within the water react with the rocks and bed and bank of the river

Attrition - where stones in transport are thrown into one another

Transportation

Solution - minerals are dissolved in the water and carried along in solution.

Suspension - fine light material is carried along in the water.

Saltation - small pebbles and stones are bounced along the river bed.

Traction - large boulders and rocks are rolled along the river bed.

When a river loses energy, it will drop or deposit some of the material it is carrying.

Deposition may take place when a river enters an area of shallow water or when the volume of water decreases - for example after a flood or during times of drought.

All of this falls in directly with the Hjulstrom curve, and melt water processes tend to be highly variable.  This is because of the highly variable nature of the discharge of these streams because they are fed by melt water.  When discharge is high erosion of sediment and channels will be high and lots of sediment will be transported.  However, when discharge falls (often daily!) deposition is encouraged.  It is for this reason that these environments and the land forms are constantly changing.

Distinctions can be made between glacial and fluvioglacial sediments and they are summarized in the table below;

A variety of landforms are associated with melt water from glaciers, including Outwash plains or Sandur, Varves, Braided Streams, Eskers, Kames and Kame terraces, Kettle holes and proglacial lakes.