lecture_9 - unstable and subject to gravity movement...

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LECTURE 9 – DEBRIS TRANSPORT AND DEPOSITION TYPES OF GLACIAL TRANSPORT glacier capacity and load capacity almost unlimited huge eratics bedrock masses load may exceed 10% near base subglacial transport by traction traction zone beneath suspension zone velocity in traction zone < basal ice transport by deformable bed transport by sheets of water mostly clay appearance of much debris englacial transport laminar flow condition with debris transport by suspension (high ice viscosity (10 14 ) englacial zone includes diffused and banded facies
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basal zone includes suspended and stratified facies source of debris slides and rock falls nunatacks, spurs erosion of glacier bed bed itself low rock knobs basal debris carried or squeezed up into ice strong compressing flow cond. -> folds? base of ice falls and glacier near glacier terminus superglacial transport most superglacial debris from englacial source referred to as ablation debris may become meters thick provides insulation
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Unformatted text preview: unstable and subject to gravity movement inversion of topography blocks up to size of houses -&gt; glacier table extraglacial transport debris flowage and rock falls/slides associated with ice margin running water and wind effects extend beyond margin DEBRIS ALTERATION DURING TRANSPORT subglacial (traction zone) some sorting in traction zone sizes silt to pebbles prefer. entrained &lt; silt -&gt; regelation &gt; pebbles -&gt; enhansed creep increasing aggreg. and size -&gt; reduced ice velocity clast alteration jointed clasts -&gt; flat irons coarse grained clasts -&gt; sperical regelation -&gt; bullet stones evolution of particle size rock frag. and mineral grain peaks controlled by terminal grade some fines removed by meltwater smooth beds -&gt; abrasion rough beds -&gt; crushing stress field -&gt; development of fabric englacial no apparent alteration perhaps fabric near base superglacial feezing and thawing -&gt; frost shattering solution -&gt; chemical wheathering no fabric...
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lecture_9 - unstable and subject to gravity movement...

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