The Sediment Cycle

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The Sediment Cycle
Erosion and transport
Weathering
Landscape
development
Lithification
Sediment sinks
Sediment movement processes
Hillslope processes
Mass movement
Channel processes
Surface water
erosion
Glacial processes
Wind erosion
Marine & coastal
processes
Mass movements
• Movement of earth materials under the force of
gravity
• Takes place in weathered rock mantle or soil
• Potential for movement depends on the strength of
the material & therefore on weathering
– Friction between ‘blocks’ or particles
– Cohesion between particles
• Depth of movement depends on change in strength
of the material with depth
• Failure plane related to changes in material
strength
Some types of mass movements
• Rock fall
• Land slides
• Mud flows
Mass movements continued.
• Importance of slope gradient: gradient
determines the action of gravity
– Characteristic stable angles for different types
of material
• Importance of water
• Role of vegetation
• Frequency of events
Surface water erosion
• Movement of loose materials on the surface (soil)
by flowing water
• Limited to smaller particles (clays to fine gravels)
• Overland flow volumes related to:
• Rainfall intensity
– Soil properties
– Vegetation cover
• Flow velocities related to:
– Slope gradient
– Surface roughness (vegetation)
– Flow depth (flow volume)
Relationship between weathering, hillslope processes and
river load
mechanical
Sediment clasts
- scree
Mass movements
Steep slopes
chemical
WEATHERING
chemical
Soil
Moderate slopes
Surface erosion
Dissolved
material solutes
Groundwater flow
RIVER
LOAD
Schumm’s (1977) sediment zones
Transfer zone
Sink zone
Source zone
Erosion = deposition
Erosion > deposition
Headwater areas
Gorges
Deposition > erosion
Foothills and lowland rivers
Flood plains
Meandering rivers
Mass movements
Braiding
Surface water erosion
REWORKING OF SEDIMENT
Deltas & estuaries
Mega fans (inland)
Off shore deposition
Topography of the Himalayas
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Copyright © 2002-2004 by Pearson Education
Sedimentation from the Himalaya Mountains
http://cwx.prenhall.com/bookbind/pubbooks/mcknight7/chapter15/essay1/deluxecontent.html
Copyright © 2002-2004 by Pearson Education
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