Glacio-fluvial landforms

Define glacio-fluvial landforms

landforms that are formed by meltwater

When do glacial periods end?

When global temperatures rise and fluctuate

Define outwash

materials deposited by meltwater

What are the characteristics of outwash?

• Finer materials

• Smoother and rounder

• Sorted

• Stratified

When do meltwater streams have a higher discharge?

in the summer months

Define jokulhaulp

extreme glacial outbursts caused by geothermal/volcanic activities

Define a Kame

hills/hummock composed of stratified sand/gravel laid down by meltwater

What are the two types of Kames?

Delta Kames, Kames Terraces

Where are Delta Kames formed?

East Lothian, Scotland

Define Delta Kames

icy land that is formed when meltwater streams flow through or around outwash

Explain the formation of a Delta Kame

• Some are formed by englacial streams emerging at the snout of the glacier. They lose energy at the base and then the deposit the load

• Others form as the result of supraglacial streams depositing material when entering the ice margin and loses energy as they enter water

Where are Kame Terraces found?

Kingsdale valley of the Yorkshire Dale

Define a Kame terrace

these are ridges of material running along the edge of the valley floor

How do Kame terraces form?

• Supraglacial streams on the edge of the glacier pick up and carry lateral moraine which is later deposited on the valley sides as a result of friction

• The streams form due to the melting of ice warmed in contact with the valley sides

Define an Esker

this is a long sinuous ridge composed of stratified sand/gravel laid down by meltwater

Explain the formation of an Esker

• Material is deposited in subglacial tunnels as the supply of meltwater decreases at the end of a glacier period

• Subglacial streams may carry huge amounts of debris under pressure in confined tunnels at the base of the glacier

• When deposition occurs pressure is released and meltwater is released at the snout and the point of deposition moves backwards

Define an outwash plain

a flat expanse of sediment in the pro-glacial area

Explain the formation of an outwash plain

• As meltwater streams gradually lose energy as they enter lowland areas beyond the ice margin, they deposit their load

• The largest material is deposited first and the finest furthest away

What are outwash plains drained by?

Braided streams

Define Braided streams

River channels that are subdivided into more channels

Explain the formation of braided streams

• The general consensus is that braided rivers form instead of meandering rivers due to a higher sediment load, caused by discharge from ablation, as well as variable rates of flow.
  At the end of a melting period, these lose water, lowering kinetic energy present in the system and therefore losing erosional power and increasing depositional power.

• This results in material being deposited into the river channel, causing it to divide in two. Braiding itself develops when this ‘mid-channel bar’ grows downstream, as a result of more, finer material being added to the bar as discharge amounts continue to decrease. These bars, during times of exceptionally low discharge like in winter months, may become home to vegetation, becoming even more permanent. whereas unvegetated bars are less stable and often move with high discharge.

• Many of these channels branch from other channels and merge to give it the ‘braided’ pattern. They are common in outwash plains due to the variable nature of ablation and meltwater amounts.

How do temperatures (climate change) affect glacio-fluvial landforms?

• As temperatures rise, more meltwater and vegetation is formed

• longer kames and bigger outwash plains and eskers

• Impacts geomorphic process as mass balance is effected

• During periods of increasing global climatic temperatures, the rate of glacial ablation increases and results in more meltwater being produced.

• This means that there is more accumulation of sediment in proglacial areas and the length of these eskers is likely to increase or become more beaded with greater and more intense ablation periods.

• With faster glacial ablation, eskers will be exposed in greater number.

• Kames: As climate change increases temperature levels, more meltwater is present, which transports and deposits sediment. This will result in a larger amount of all types of kame being more likely to form.

What is the impact of climate change on braided streams?

• Due to climate change, braided streams may dry up due to smaller amounts of ice present in these areas, after an initial increase in ablation due to temperature rise. This initial increased sediment load will progressively decrease as the ice mass decreases.

• As a result, there can be expected to be more eroded streams, being deeper and wider, inside this outwash plain, followed then by the area becoming dry and tundra-like. Whilst vegetation thrives in outwash plains due to the rich minerals present in the glacial meltwater, this may also dry up in the future, becoming a barren, sandy and gravelly area with little life, or could be taken over and reclaimed by plants depending on resource availability.

Post-glacial modification

Upland elevations and continued fluvial processes; isotonic readjustment due to no pressure

Define a Kettle

A kettle is a large depression in the ground formed by glacial deposition

How are Kettles formed?

When large blocks of ice become stranded and buried by deposited as meltwater flows around it. The water evaporated leaving only the depression.