GEOS300 Quiz Question (post-midterm)

T/R: If a channel is described as being ‘detachment limited’, then this implies that it is much harder to detach sediment than it is to transport sediment

True

Which of the following terms would be used to describe a channel where it is harder to transport sediment than it is to detach it?

Transport-limited

The correct units associated with total discharge are Pa?

False (its m³/s)

Sediment entrainment tends to occur when the Shields stress is greater than which of the following?

>0.045

T/R: The Froude number can be used to determine the dominance of bed load and suspended load

False (its the Rouse number)

The bedload sediment flux can be expressed as a power law function of which of the following?

Shear stress, hillslope gradient, channel curvature, mean annual precipitation

A sediment rating curve describe the relationshop between?

Discharge and suspended-sediment concentration

T/R: Transport capacity refers to the amount of sediment that can be transported by a flow

True

Vegetation is one of the three primary controls on a river’s ability to transport sediment in suspension.

False (its shear stress, flow depth, grain size)

Which of the following (select all that apply) are major factors that control sediment detachment and transport on hillslopes and in low-order valleys?

Rainfall, vegetation cover, soil texture, slope

T/R: Cascade channel reaches are characterized by a high d90 to flow depth ratio

True

T/R: Distal progradation of alluvial fans is an expected outcome when flood capacity (transport capacity) is low and sediment supply is low?

False

What is the primary reason for the formation of alluvial fans?

Decreases in flow depth due to loss of channel confinement

T/R: The sediment delivery ratio generally increases with increases in drainage area?

False

A change in base level results in which of the following in a bedrock channel?

A knickpoint

T/R: Knickpoints maintain their shape and propagate upstream over time in alluvial channels

False

T/R: High uplift rates can lead to a decrease in accommodation space for sediment and therefore to larger alluvial fans?

False

A sediment-flux driven model for bedrock channel erosion is most appropriate to use when…

Abrasion is the dominant erosion process

T/R: Channel slope decreases as drainage area increases

True

T/R: Fluids with a yield strength are only mobile when the shear stress at the base of the flow exceeds the yield strength

True

T/R: Debris flows that are less mobile tend to have a greater yield strength and deposit sediment near the fan apex

True

T/R: Debris flows continue to flow as long as shear stress exceeds yield strength.

True

Which of the following is the leading conceptual model for climatic control of terrace formation on alluvial fans in the southwest US?

Humid-to-arid transitions trigger loss of vegetation cover, leading to excavation of sediment stored on hillslopes during the previous humid interval.

T/F: Yield strength of debris flows varies from 50-5000+ Pa and is a function of sediment concentration

True

Which of the following is NOT commonly used as a way to classify delta morphology?

Supply-dominated

T/R: Avulsions are common on both alluvial fans and deltas

True

T/R: River-dominated deltas tend to have smooth shorelines and a smaller number of long channels, due to longshore transport of sediment delivered by the river

False

Which of the following is NOT a primary control on the mass discharge of sand along the coast (ie. sand transported by longshore drift?)

Temperature

(primary controls are wave breaker height, angle between breaker line/shoreline, gravity)

T/R: Wave speed depends on water depth and is greater when water depth is greater

True

T/R: A drift cell is a self-contained coastal unit where sediment movement is primarily confined within its boundaries

True

T/R: The law of the wall tells us that wind velocity at a given point above the ground is proportional to the square root of the distance from that point to the ground

False

The aeolian saltation flux is proportional to which of the following?

Shear stress

Which of the following are primary controls on dune type?

Sand supply, rainfall, slope, variability in dominant wind direction

T/R: Barchan dunes form in settings with limited sand supply and unidirectional wind

True

T/R: Parabolic dunes form when vegetation grows on horns of star dunes

False

Which of the following is an essential process leading to yardang formation?

Aeolian abrasion

Which of the following is a good description of a desert pavement?

A surface that is covered with closely packed, interlocking rock fragments

T/R: The time required for desert pavement formation can vary with soil texture

True

T/R: Lateral moraines can be used after a glacier melts as an indicator of the maximum thickness of the glacier

True

T/R: The viscosity of ice is greater when temperatures are cooler

True

Ice can be modeled as which of the following types of idealized fluids?

Perfectly plastic fluid

The rate of abrasion at the base of a glacier is proportional to…

None of the above (according to the options on the quiz. But the answer is square of the sliding velocity)

T/R: Glaciers move as a result of basal sliding and internal deformation

True