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Geomorph Final
| Question | Answer |
|---|---|
| Material/sediment that moves downslope without the aid of flowing water is | colluvium |
| The ability of material on a slope to resist downslope stresses is | shear strength |
| Shear strength is a function of what? | pore pressure, cohesion, normal force |
| Particle size and shape affect shear strength and this is expressed mathematically as part of | internal friction angle |
| The normal stress between grains on a slope can be effectively reduced by | pore pressure |
| Dry, loose sand has a cohesion of _____ kPa, while clay may have a cohesion of around _________ kPa, depending on conditions. | 0, 100 |
| Positive pore pressures occurs where? | in the phreatic zone |
| The diffusive process that is especially important in areas with less vegetative cover, and moves sediment both up and down the slope, but with net downslope movement is | rainsplash |
| Mass wasting can be categorized as a _______ if there is no failure plane and it behaves in a viscous manner. | flow |
| Mass wasting can be categorized as a _______ if there is motion along a well-defined surface. | slide |
| Mass wasting can be categorized as a _______ if the material maintains little contact with the underlying slope. | fall |
| Factor of safety = | shear strength over shear stress |
| "Pistol butt" trees are formed as a result of what? | soil creep and vertical velocity gradient |
| A rapid flow with < 40% water content is what? | slurry |
| A rotational "slide" in which material is translated almost intact is | slump |
| A dry flow in which fragmented rock moves rapidly downslope is | rock avalanche |
| A model for slope stability that assumes a mass on a perfect, uniform plane and ignores lateral effects is | infinite-slope model |
| Rotational slope stability can be modeled with | method of slices |
| Where soil production rates exceed the average downslope transport rates, the slope is called | transport-limited |
| Slopes that are convex in profile or cross-section tend to be __________ when looking at them in map or plan view. | divergent |
| TRUE or FALSE: Meandering streams are not known to exist in the geologic record before about 400 Ma, when land plants radiated. | False |
| Unconsolidated material transported and sorted by stream flow is called ____________. | alluvium |
| Upland channels that tend to have __________ sediment cover. | little |
| Mountain/upland streams tend to have transport capacities that exceed the amount of sediment available for transport, which is called | supply-limited |
| A stream with sinuous active threads separated by ephemeral (temporary) gravel and sand bars is | braided |
| A section of channel that exhibits similar characteristics throughout is a(n) | reach |
| _______________________ describes the channel width and depth corresponding to a given discharge at a particular location along the stream. | hydraulic geometry |
| The _____________ is always the deepest part of the flow. | thalweg |
| In many attempts to accurately measure bedload, efforts are complicated by | presence of the measurement device alters the flow and bed dynamics in that location |
| TRUE or FALSE: Woody debris in some streams can be as important a factor in stream evolution and morphology as sediment supply. | True |
| The wetted perimeter times the average depth and average flow velocity is | discharge |
| Suspended sediment that does not settle from suspension over a period of days or weeks or longer is | washload |
| Lowland stream systems tend to | store much sediment in valley bottoms |
| One way to predict sediment erosion from a channel bed is to compute bed shear stress and compare to ___________, which involves the Sheilds parameter. | critical shear stress |
| A __________ stream has a longitudinal profile that is adjusted to carry its sediment load (flux in = flux out). | graded |
| In a flow that is 3.0 meters deep, the average velocity would be measured at _____ meters from the surface. | 1.8 |
| Lowland streams tend to have sediment in abundance of what can be transported. This is known as | transport limited stream |
| Concrete channels accommodate _________ discharge than a natural stream containing a rocky bed | greater |
| For sediment to remain in suspension, the (Stokes) settling velocity (and associated forces) must | less than upward (turbulent eddy) forces |
| Most large rivers carry most of their total load as (of course, there are exceptions) | suspended load |
| ______________ occurs when a stream finds a more direct and higher potential energy route (steeper gradient) between two points. | avulsion |
| In upland streams, ___________ usually accounts for most sediment supply to the stream. | mass wasting |
| The ratio of total channel length vs the length of its stream valley is | sinuosity |
| The downslope component of the weight of overlying water that pushes on sediment on the channel bed is | bed shear stress |
| ___________ is an empirical measure of the (frictional) resistance to flow in a stream channel arising due to the character of the channel. | roughness |
| Meandering streams are characterized by | point bars and helical flow |
| TRUE or FALSE: Some large rivers carry most of their load as dissolved load. | True |
| Given two streams, if slope and channel geometery configuration were the same, the lowest flow velocities would occur in the stream that | had logs/woody debris |
| In lowland streams, ___________ and upstream channel erosion often account for most sediment. | local bank erosion |
| Shallower portions of a stream, often exhibiting a turbulent surface are | riffles |
| Permafrost | Ground below 0o C for > 2 consecutive years, Can extend to depths of 1.5 km |
| Tundra | (arctic and alpine) treeless, low-growing vegetation |
| Taiga | coniferous trees |
Created by:
JackPitt