FLUVIOGLACIAL DEPOSITION LANDFORMS <ul><li>Outwash Plains </li></ul><ul><li>Braided Streams </li></ul><ul><li>Varves </li></ul><ul><li>Kames </li></ul><ul><li>Kame Terraces </li></ul><ul><li>Kame Deltas </li></ul><ul><li>Eskers </li></ul>Photo sources credited where known – for educational use only.
<ul><li>- Lie below snout of glacier – composed of glacial sands & gravels deposited by meltwater streams. </li></ul><ul><li>Outwash plains are formed in the following way: </li></ul><ul><li>Meltwater streams rush through the terminal moraine picking up rock pieces. </li></ul><ul><li>The streams then drop these pieces beyond the terminal moraine as they slow down. </li></ul><ul><li>The largest pieces are dropped first, for example gravel, followed by smaller ones, for example sand. </li></ul><ul><li>These areas of sand and gravel, rounded and sorted by meltwater, are called outwash plains . </li></ul>1. OUTWASH PLAINS EXAMPLES: Kelling Heath and Salthouse Heath – North Norfolk
Remember – sands and gravels on outwash plains are sorted and graded! Source: http://uregina.ca/~sauchyn/geog323/342.jpg
Kettleholes <ul><li>Kettleholes form in the following way: </li></ul><ul><li>As the glacier retreats it may leave large blocks of ice. </li></ul><ul><li>These blocks of ice become buried as sediment builds up around them </li></ul><ul><li>This ice slowly thaws over time and the covering gravel collapses leaving a depression. </li></ul><ul><li>These depressions are called kettle holes . </li></ul><ul><li>If the depressions are deep enough to tap the water table a kettle hole lake forms. </li></ul><ul><li>Kettle Lakes can vary enormously in size: </li></ul><ul><li>Ellesmere – Shropshire – there are a large number of kettle lakes with a diameter of over 100m. </li></ul><ul><li>Iceland – in front of Solheimajokull there are a large number of kettle holes no greater than 15m in diameter. </li></ul>
These form on outwash plains and occur where channels of meltwater get become clogged by course deposits. This encourages the stream to divide and braid. They are common in outwash areas due to seasonal fluctuations in discharge. 2. BRAIDED STREAMS Source: http://pubs.usgs.gov/of/2004/1216/b/images/braided2.gif <ul><li>At the end of the melting period melt water streams carry large amounts of material that are deposited in the channel </li></ul><ul><li>This causes the channel to divide and then rejoin with mid-channel bars growing </li></ul><ul><li>Largest materials is deposited first as discharge decreases </li></ul><ul><li>At times of low discharge vegetation may stabilise the bar and the bars may become permanent </li></ul><ul><li>If un-vegetated the bars may however form and reform during different discharge events. </li></ul>
3. VARVES These are the vertical stratification of sediments and are found in the bottom of pro-glacial lakes. Sediment carried by meltwater streams is deposited when water enters a pro-glacial lake as the energy of the stream is lost. Meltwater streams vary in discharge seasonally and Varves have alternative sequences of coarser (sand and gravel) and finer (clay and silt) bands. 1. Coarse sediment – deposited in summer (greatest because of fast melting – higher energy – larger material transported) 2. Finer sediment – deposited in winter – little or no coarse sediment washed into lake Each pair of varves represent’s a year’s accumulation (can therefore count varves to calculate age of sediment) Thickness varies (according to weather – can indicate climate change fluctuations) – thicker bands – indicate warmer conditions – more meltwater and more load – if darker – may indicate more organic matter and again therefore warmer conditions.
4. KAMES, KAME TERRACES & KAME DELTAS These are ice-contact stratified drift features – deposited in the vicinity of melting ice and partly sorted by water. <ul><li>4.1 KAMES </li></ul><ul><li>Mound like hills composed of sands and gravels – formed as meltwater streams on the surface of the ice plunge down crevasses taking sediment with them – form accumulation of material in the crevasses – left behind when ice melts. </li></ul><ul><li>As they are unsupported – often collapse when ice retreats and the shape is much altered. </li></ul>EXAMPLES: East Lothian – Scotland (a few hundred m long & tens of m high) Source: http://www.uwsp.edu/geo/faculty/ritter/glossary/h_k/kame.html
<ul><li>Flat topped ridges formed of alluvial material deposited along the edge of the valley glacier (as a result of streams plunging down the edge between the ice and the valley slope) </li></ul><ul><li>small troughs form here as the valley slopes heat faster and more than ice – causing melting of ice in contact with the warmer hills – similar to lateral moraine – but SORTED material. </li></ul><ul><li>EXAMPLES : Columbia Icefield & East Lothian, Scotland </li></ul>4.2 KAMES TERRACES Source: http://www.fettes.com/Cairngorms/glacial%20landscapes%20deposition.htm 4.3 KAME DELTAS These are fan shaped mounds containing debris from ice and Fluvioglacial material. They are formed when glacial streams enter a pro-glacial lake. Where supra and en-glacial streams emerge at the snout and enter a pro-glacial lake they lose energy and deposit their load..
5. ESKERS These are long sinuous ridges of land – composed of sands and gravels – they can be 20-30m high and can meander across the landscape for many km. <ul><li>Eskers are formed in the following ways: </li></ul><ul><li>A meltwater stream follows a tunnel beneath the melting glacier. </li></ul><ul><li>The stream carries and deposits moraine, filling up the tunnel. </li></ul><ul><li>When all of the ice melts, a long ridge of moraine is left in the shape of the stream’s tunnel </li></ul><ul><li>It is likely that deposition occursed where streams emerged from beneath the ice and were no longer constrained – deposition occuring as the ice was in retreat </li></ul><ul><li>Beaded eskers can reflect times of higher and lower discharge. </li></ul><ul><li>Often excavated for sands and gravels therefore not always distinctive in the landscape. </li></ul><ul><li>EXAMPLES: </li></ul><ul><ul><li>Eskers are found near Dublin in the Trim area </li></ul></ul><ul><ul><li>Also good examples in Nova Scotia – Canada. </li></ul></ul>