Crisesaftermidterm1

Crisesaftermidterm1 - RiversandFloods 18:02...

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Rivers and Floods 18:02 Most powerful agent of erosion When evaporates, salts left behind and what’s left is pure, accumulates, then  erodes land Becomes ground water Continuous cycle All water on Earth is used Why important? Balance of nature o Sediment source for beaches o Soil nutrition o Wildlife Source of fresh water Floods – we live on floodplains o Supposed to flood o Levees to channelize our streams and not do what’s natural Issues Rivers are supposed to flood Levee breaks take on unnatural conditions Water on Earth Not much fresh water on Earth, most of it is ice Downstream Changes
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Coming down we find that the width of the river gets larger, depth gets deeper,  velocity increases  Stream Cross Section Meanders, asymmetry to its depth, deeper on outside of turn, that’s where the  river erodes, always eroding and depositing sediment Changing positions all the time throughout their flood plains River erosion and deposition Rocks rolling around and get rounder and smoother Erosion on outside turn Rivers and gravity work together, mass wasting, rocks from landslide fall into  stream where they start getting rounded Deposition on the inside turn Rivers and streams shifting where they are, back and forth cutting into the  land Extending themselves upward Conglomerate Becomes sediment Youthful Streams Evidence of floods? V-shaped valleys o Land is eroding today what plate tectonics built Uplift vs. Erosion Uplift is faster If erosion was faster we wouldn’t have any mountains Mature stream
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Trees on the rivers edge o On a Naturally Levee Full of boulders and sand, leave it natural and the trees love it Old Age stream You could have no idea you’re on a floodplain Deposition at the base River comes out and deposits a delta, part will be above water lever,  deposited during the flood when levels were higher Artificial base = dam Impact of dams Issues Don’t live on flood plain or be in a canyon when it might flood, don’t hike it if there  are dark clouds Flood recurrence interval Flood recognition Topography – flood plains, oxbow lakes Recent o Debris o San bars o Gravel and boulders Carved by running water Historical o Gravel and sand intervals, date by C-14 o Flood hazard maps
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Air Pollution and Global Warming 18:02 Air Pollution – 3 rd  World – Al Gore’s book
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Air Pollution and Global Warming 18:02 Poland Romania N. Czech Ukraine Mexico City Two types of Air Pollution Combustion   carbonic acid, sulfuric acid, etc. = acid rain When petroleum has sulfur it creates sulfur dioxide
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Crisesaftermidterm1 - RiversandFloods 18:02...

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