Fluvioglacial Landforms EQ3: How do glacial processes contribute to the formation of glacial landforms and landscapes? LO: To understand how fluvioglacial features are formed, with a particular focus on the difference between ice contact and proglacial features. You have in front of you all the features you are going to learn about today. See if you can sort them as follows… Ice contact and proglacial fluvioglacial features With their correct names: delta kame, kettlehole, esker, kame terrace, sandur (outwash), varve, proglacial lake
Ice Contact Features Eskers Appearance: Long, sinuous (lots of curves and turns) ridges on the valley floor. Formation: Material is deposited in subglacial tunnels as supply of meltwater decreases when glacier is at end of glacial period. Subglacial streams carry sediments under pressure within tunnels. When glacier retreats, sediments slump into a mound.
Ice Contact Features Delta Kames Appearance: Small mounds on the valley floor (steep sided and conical in shape). Formation: Deposition of material in a hollow e.g. a crevasse or moulin. As the ice melts, the kame emerges as a hump of sediment. Slumping may occur when no longer supported by ice. Closely linked with kettleholes.
Ice Contact Features Kame Terrace Appearance: Ridges of material running along the edge of the valley floor. Formation: Sediment accumulates in ponds and lakes trapped between lobes of glacier ice. Sometimes between a valley glacier and the valley side.
Proglacial Features Kettleholes Appearance: Small circular lakes in outwash plains, often with water in the bottom. Formation: Blocks of ice get separated from the main glacier (ice may have stagnated then retreated, or ice blocks may have been washed out from glacier during jokulhaup. Isolated blocks of ice become partially or wholly buried by outwash material. Ice blocks eventually melt and leave behind holes or depressions that fill with water to become the kettlehole.
Proglacial Features Sandur (outwash) Appearance: A flat expanse of sediment in the proglacial area. Formation: Meltwater streams gradually lose energy (discharge decreases). Material is deposited over a vast expanse. Largest material near snout, finest further away (horizontally sorted).
Proglacial Features Proglacial Lakes Appearance: Sometimes known as ice margin lakes – a lake at the snout of the glacier. Formation: Formed at the front of glaciers where meltwater from the glacier becomes impounded. Bound by an area of high ground (sometimes a terminal moraine). Temporary features (ephemeral) dependent upon rate of glacial retreat.
Proglacial Features Varves Appearance: Stratified sediments found at the bottom of glacial lakes. Formation: Sediment carried by meltwater streams is deposited when they reach the lake. Larger layers represent summer (lots of meltwater available). Smaller layers represent winter (not as much meltwater).
Turn to page 87/88 and make some additional notes. HOMEWORK There is some good information in the textbook about examples of proglacial lakes. Turn to page 87/88 and make some additional notes.