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76 Cards in this Set
- Front
- Back
Fluid flows of grain aggregates, moving primarily due to gravity.
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sediment-gravity flows
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Turbulence is a __________ mechanism.
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support
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In debris flows, the _________ of the matrix is its support mechanism.
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strength
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In grain flows, grain ________ is its support mechanism.
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collision
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In fluidized flows, _________ is its support mechanism.
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buoyancy
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In turbidity currents, _________ is its support mechanism.
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turbulance
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An example of a grain flow is an _________.
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rock avalanche
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An idealized material that behaves like a rigid mass under low levels of stress, but behaves like a Newtonian fluid above a critical amount of sheer.
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Bingham plastic
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Within the body of a flow, there is no movement of grains with respect to each other and behaves like a rigid mass.
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plug flow
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What is the formula for sheer stress (τ) in plug flows?
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τ = τc + μs (dU / dy)
τc = critical sheer stress μs = viscosity of flow dU/dy = change of velocity |
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What initiates debris flows?
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Usually heavy rains or some other sudden, rapid flow where there is not a lot of vegetation and loose sediment.
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Where do debris flows usually happen?
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In deserts where there is loose soil and sediment with not a lot of vegetation.
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What is the Bagnold effect?
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When grains flow down and expand when they hit each other (called dynamic dilatancy)
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Collisional interaction of grains as they move relative to each other and expand as they flow.
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dynamic dilatancy
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The maximum slope angle (β) just before slope failure, or initiation of flow.
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angle of internal friction (φi)
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Formula for angle of internal friction?
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τ / σ = tan φi
τ = sheer stress σ = upward-directed normal stress φi = angle of internal friction |
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When fluid is introduced into the sediment from below (i.e. baseflow in streams).
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fluidization
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When fluid is internal and moves up due to changes in packing (i.e. earthquake-induced sand volcanoes).
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liquidization
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What is an example of fluidization?
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groundwater moving up into streams through porous sediments, baseflow in streams
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What is an example of liquidization?
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sand volcanoes
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When silt and clay are suspended in air it is a __________.
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duststorm
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When snow is suspended in air it is a __________.
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snow avalanche
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When mud is suspended in water it is a ___________.
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turbidity current
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Vertical change in grain size with decreasing velocity.
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graded bedding
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Vertical change in sedimentary structures with decreasing velocity.
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Bouma sequence bedding
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Grain-supported rudite textures.
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orthoconglomerates
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Matrix-supported rudite textures.
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paraconglomerates
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Conglomerates can also be called _________.
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roundstones
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Breccias can also be called _________.
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sharpstones
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Rudites with one kind of grain.
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oligomictic
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Rudites with many kinds of grains.
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polymictic
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Rudites produced by weathering and sedimentation.
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epiclastic
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Epiclastic rudites formed outside of a basin.
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extraformational (extrabasinal)
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Epiclastic rudites formed inside a basin.
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intraformational (intrabasinal)
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Rudites produced by explosive volcanic eruptions.
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pyroclastic
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Rudites produced by tectonic stresses.
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cataclastic
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Rudites produced by collapse or karst-related structures.
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autoclastic
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Rudites produced by impacts.
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impact breccias
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A large-scale feature of a sediment or sedimentary rock, usually seen and best-studied in outcrop-scale view rather than hand sample.
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sedimentary structure
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What is a use of sedimentary structures?
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Using structures, you can infer the process and environment from which it was formed.
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One individual structure; individual element of a bed configuration.
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bed form
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The entire sedimentary structure.
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bed configuration
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Why are there bed configurations?
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We don't know exactly why they exist.
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When sediment gets finer as you go upward.
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fining upward sequence
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Structures formed at the time or very soon after deposition.
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primary structures
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What are some examples of primary structures?
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layering, cross-bedding, ripple marks, mud cracks
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Structures formed at some time (usually a long time) after deposition, typically during burial.
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secondary structures
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What are some examples of secondary structures?
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concretions, nodules, geodes
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Structures formed by the activity of organisms.
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biogenic structures
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What are some examples of biogenic structures?
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tracks, burrows, trails, trace fossils
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Can biogenic structures also be primary structures?
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Some people believe so.
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Formed under water.
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subaqueous
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Formed on land.
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subaerial
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Bedforms with straight crestlines, constant crest and trough elevations, and identical cross-sectional profiles at all locations along the crestline.
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2-D bedforms
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Bedforms with sinuous crestlines, sinuous troughs, or variable cross-sectional profiles along the crestline.
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3-D bedforms
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Bedforms that are planar.
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plane beds
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Dunes that migrate upstream (backwards).
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antidunes
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Antidune length is a function of flow _________.
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velocity
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When current erodes the bottom in some way and makes a mark.
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sole marks
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Marks made by an object.
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tool marks
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What are some examples of sole marks?
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flute casts, rill marks, current crescents
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What are some examples of tool marks?
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groove marks, brush marks
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When crystals grow in sediment (gypsum or ice) they form what bedding-plane structures?
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crystal imprints
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When soft sediment sinks into a soft layer of sediment below it.
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load casts
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A layer of constant lithology.
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bed
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The surface of a bed.
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bedding plane
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The thickness of sediment deposited under constant physical conditions; can be a series of beds.
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sedimentation unit
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What are some causes of bedding?
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variations in grain composition, grain-size, grain shape, fabric, or packing
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Lunate ripples are also called __________.
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barchan dunes
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Current ripples are _________.
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asymmetrical
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Oscillation ripples are __________.
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symmetrical
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When the tool approaches the sediment surface at a low angle and immediately bounces back into the current.
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bounce marks
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The tool approaches the sediment surface at a very low angle, with the axis of the tool inclined upcurrent, and is then lifted away by the current, producing a ridge of mud downcurrent of the mark.
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brush marks
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The tool reaches the sediment surface at a fairly high angle and is then lifted up and away by the current.
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prod marks
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The tool rolls over the sediment surface.
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roll mark
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The tool travels downcurrent with a saltating movement, hitting the sediment surface at near regular intervals.
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skip marks
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