glacial landforms changing w climate + fluvio landforms Flashcards
how are fluvial glacial landforms created?
produced by meltwater from glaciers
how is this environment created in the immediate wake of a glacial period?
ablation begins to dominate the glacial system and glacier melts and retreats as long term climatic conditions alter
what is the importance of glacial meltwater?
- melting snow helps to enlarge the shallow nivation hollows that eventually become corries
- helps to lubricate the base of the glacier
- transports moraine beneath a glacier, tools for erosion
- if it refreezes, it can bind the base to broken fragments
- often forms river- both below and atop
- erode channels and form distinctive depositional features
what is outwash?
the distinctive sediment only deposited by glacial meltwater
how is outwash different to till?
- smaller- meltwater streams have less energy so carry finer material
- smooth and rounded- by contact with water and by attrition
- sorted- horizontally with largest material further up valley
- stratified- vertically with distinct seasonal and annul layers
what are Kames?
hill or hummock composed of stratified sand and gravel laid down by glacial meltwater
what is the sediment of a kame like?
the sediment consists of sand and gravels and builds up into mounds as the ice melts and more sediment is deposited on top of old debris
what will often happen to Kames?
they will collapse when the ice melts back and leaves mounds unsupported
What are Kame terraces and how are they formed?
differential specific heat capacity of the valley and glacier, leading to supraglacial streams which deposit material along the valley side
what happens to kame terraces in the summer
when the walls warm up in the summer the warm rock helps to melt the ice nearest to it, forming a long depression or trough along which meltwater flows
why are deposits sorted in kame terraces and how does this make a kame identifiable?
because they are transported by water which allows them to be distinguished from lateral moraine deposits which exhibit no sorting
what are Eskers?
long, sinuous ridges composed stratified of sand and gravel laid down by glacial meltwater
how are Eskers formed?
- material is deposited in subglacial tunnels as the supply of meltwater decreases (may carry huge amounts of debris under pressure in confined tunnels at the base of the glacier)
- the snout retreats, the point of deposition will gradually move backwards
- leaving behind a long sinuous ridge composed of stratified sand and gravel
What is an outwash plain?
an extensive, gently sloping area of sand and gravel that form in front of a glacier
what is an outwash plain a result of?
result of the outwash of sediment carried by meltwater streams and rivers losing their energy
what is the composition of outwash plain?
coarse material which is found near to the glacier, and finer clay, which is carried across the plain before being deposited
how are outwash plains drained?
typically drained by braided streams, river channels subdivided by numerous isles and channels
how are braided channels formed?
- begin with a mid-channel bar which grows downstream, discharge decreases after a flood and the coarsest particles are deposited
- as discharge decreases finer material is then added to the bar
- when exposed channel bars are stabilised by vegetation and become more permanent features
what happens to unvegetated bars?
they are unstable and often move, form and reform with successive flood
named example and dimensions of an esker
trim esker near Dublin
14.5km long, 4-15m tall
named example and dimensions of Kame
yorkshire dales , 2km long 2m high
when is a glacial fluvio period?
exist as a result of climate change at the end of glacial periods
during inter glacial lasting 10,000-15,000
how are glacial fluvio landforms formed?
produced by meltwater released during deglaciation
how is a delta kame formed?
en-glacial streams losing energy at the
base of a glacier or a supraglacial stream
losing energy as it enters a ice marginal static lake
deposits material as it loses energy
eg East Lothian, Scotland
discharge in meltwater rivers
have high discharge in the summer months and lower in winter
eg glacier d’Argentière
discharge is 0.1-1.5 cumecs in winter
but 10-11 cumecs in summer
how does volcanic activity impact discharge levels?
jokulhaulps - volcanic activity below a glaciers causing sudden melting
eg after 2010 eyjafjallajokul discharge was 2500 cumecs
what do beaded eskers show?
larger beads imply slower rate of retreat
modification of glacio fluvial landforms
repeated advance and retreat of glaciers erode and change shape of landforms
colonisation by vegetation - increased chemical weathering eg chelation
temperatures rise = more accumulation of outwash material in pro glacial zone
kames and eskers exposed in greater length during retreat
eg Sòlheimajökull retreating at 100m/year, a pro-glacial lake may form at snout
