particle deposition
DESCRIPTION
Particle Deposition. Settling rate -- the speed at which a particle will settle to the bottom of a body of water (deposition). There are 3 factors which affect the settling rate of a particle. - PowerPoint PPT PresentationTRANSCRIPT
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Particle DepositionParticle Deposition
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Settling rate -- the speed at which a particle will settle to the bottom of a body of water (deposition)
There are There are 3 factors3 factors which affect the which affect the settling rate of a particlesettling rate of a particle
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1) Size – The smaller the particle (clay, silt) the slower it will settle out. Larger sediments (cobbles, boulders) will settle quickly.
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As the stream slows down, the larger As the stream slows down, the larger particles settle first…particles settle first…
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2) Shape – Rounder, more spherical particles settle out faster than flat, angular or irregularly shaped particles.
Why is this? Friction is decreased when a particle is rounded and therefore it settles faster. It’s like it’s more aerodynamic - like a sports car. But in this case, it’s hydro-dynamic.
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Hydrodynamic particles (round) settle Hydrodynamic particles (round) settle faster than flat or irregular shaped faster than flat or irregular shaped
particles particles
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3) Density – If two particles have the same basic size and shape, the denser particle will settle faster.
Which will settle faster – a glass marble or a lead marble? (PS – they are the SAME SIZE marble…)
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Settling Rate vs. Settling TimeSettling Rate vs. Settling Time
There is an inverse (indirect) relationship between settling rate and settling time. Think about it, sediments that settle at a faster rate (rate increases) require less time to settle (time decreases)
Time to settle (sec)Settl
ing
Rat
e (c
m/s
ec)
Remember what the graph of an inverse relationship looks like…
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Sorting of Deposited Sorting of Deposited ParticlesParticles
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Final deposition of particles (sediments) usually occurs at the mouth of a stream. This is due to the faster flowing stream emptying into a slower larger body of water.
Horizontal sortingHorizontal sorting takes place. The sediments that were once carried down the stream are arranged from largest to smallest.
Horizontal SortingHorizontal Sorting
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More Horizontal SortingMore Horizontal Sorting
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Vertical SortingVertical Sorting
Happens in QUIET WATER (still – lake, pond) Particles sort out from bottom to top in layers On bottom – largest, roundest, densest particles On top – smallest, flattest, least dense particles Can occur when a depositional event, like a landslide, dumps a large volume of unsorted sediments into a still body of water like a lake It creates “graded beds” of sediments
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Vertical Sorting: Graded BeddingVertical Sorting: Graded Bedding
One depositional event
One depositional event