Earth Mat Flashcards - Ch 11

Question 1

__________________ are the solid products of weathering, the breakdown of rocks at or near Earth’s surface.

Answer 1

Detrital sediments

Question 2

are the solid products of organic synthesis or precipitation and include hard materials such as shells, bones, and teeth, and soft materials such as cellular materials composed of organic molecules.

Answer 2

Organic sediments

Question 3

are the solid products of inorganic precipitation, such as mineral crystals precipitated from solution.

Answer 3

Chemical sediments

Question 4

is a general term for solid sedimentary particles regardless of origin.

Answer 4

Clastic

Question 5

The term _________ is used for clastic sediment that is transported as solid particles across Earth’s surface.

Answer 5

epiclastic

Question 6

clastic particles of organic origin such as shell fragments transported by waves or currents.

Answer 6

bioclastic

Question 7

refers to clastic particles composed of silicate minerals.

Answer 7

Siliciclastic

Question 8

is used for clastic particles produced initially by volcanic processes.

Answer 8

Volcaniclastic

Question 9

refers to clastic sediment derived from a land mass.

Answer 9

Terrigenous

Question 10

The _____________is a simple model of the processes responsible for the production of sediments and sedimentary rocks.

Answer 10

sedimentary cycle

Question 11

Two major types of weathering processes are recognized:

Answer 11

Disintegration processes, which break rock materials down into smaller pieces of the original material without changing their composition.
Decomposition processes, which change the composition of the original material, producing new materials

Question 12

The products of a second sedimentary cycle are referred to as ____________ sediments and sedimentary rocks.

Answer 12

polycyclic

Question 13

Cross strata form when sediments accumulate on steeper slopes of up to

Answer 13

35°.

Question 14

depositional environments may be broadly subdivided

Answer 14

into terrestrial, transitional (paralic), and marine environments.

Question 15

environments typically occur in the terrestrial-marine transition and include coastal-deltaic environments such as deltas, estuaries, tidal flats, beaches and back-beach dunes, and barrier island-lagoon systems.

Answer 15

Transitional (paralic)

Question 16

In _________________ which possess shear strength, the major stress that initiates flow is the tangential force of gravity (gₜ), which increases with increasing slope angle.

Answer 16

plastic flows,

Question 17

Flows may also be distinguished as

Answer 17

laminar or turbulent flows

Question 18

In __________ flow, adjacent parcels of the flow move roughly parallel to one another in a well-organized pattern, with negligible mixing between them.

Answer 18

laminar

Question 19

In __________ flow, adjacent parcels of the flow move in chaotic patterns, and random mixing between parcels is common.

Answer 19

turbulent

Question 20

Water is a Newtonian fluid.
T or F

Answer 20

T

Question 21

Like all fluids, Newtonian fluids lack shear strength, but they are characterized by a constant resistance to shear stress, called

Answer 21

dynamic viscosity (μ).

Question 22

Colder water possesses more molecular bonds between molecules, resulting in

Answer 22

higher viscosity or resistance to flow.

Question 23

is essentially a ratio between the inertial forces and the viscous forces in a fluid medium.

Answer 23

Reynolds’ number

Question 24

The Reynolds’ number can be used to predict

Answer 24

whether flow will be laminar or turbulent.

Question 25

Viscous forces tend to damp out turbulence and favor

Answer 25

laminar flow.

Question 26

Inertial forces tend to favor the development of

Answer 26

fluid turbulence.

Question 27

For any situation, there is a critical Reynolds’ number below which flow is ________ and above which flow is ___________.

Answer 27

laminar; turbulent

Question 28

The process by which epiclastic sediment transportation is initiated by erosion is called

Answer 28

entrainment.

Question 29

Hjulstrom’s diagram contains two curves that divide the diagram into three fields.

Answer 29

Upper Curve : Erosion/Entrainment Curve
Lower Curve : Threshhold Depositional Velocity

Question 30

Why does the critical entrainment velocity increase with decreasing particle size for silt and clay?

Answer 30

Due to increasing cohesiveness from higher surface area-to-volume ratios and electric charge on particles.
Their cohesiveness makes them more difficult to entrain, similar to larger particles.

Question 31

What does the central field between the critical entrainment and deposition curves on Hjulstrom’s diagram represent?

Answer 31

The transportation or at rest field.

Question 32

What happens to particles in the central field of Hjulstrom’s diagram when flow velocity is decreasing? increasing?

Answer 32

Particles continue to move until the velocity drops below the threshold velocity for deposition:
Particles continue to be deposited until the velocity surpasses the critical entrainment velocity

Question 33

Once entrained, the _______________ of different particle sizes tends to be carried in different parts of the flow.

Answer 33

sediment load

Question 34

The ________________ is carried in continual or intermittent contact with the bed over which the water is flowing.

Answer 34

bed load

Question 35

The bed load is subdivided into:

Answer 35

A traction load, which is in continual contact with the bottom.
A saltation load, which is in intermittent contact with the bottom.

Question 36

contains the coarsest particles, those with sufficient mass that they are not lifted from the bottom by turbulence and lift forces.

Answer 36

The traction load

Question 37

Particles in the traction load move down-current by:

Answer 37

Rolling, sliding, creep

Question 38

Where the traction load is more than one particle deep, the term ___________ can be used.

Answer 38

traction carpet

Question 39

The_____________ contains smaller, less massive particles that can be lifted from the bottom by turbulence, lift forces, and particle impacts but quickly settle back to the bed before being lifted again.

Answer 39

saltation load

Question 40

The ___________ contains the smallest, least massive particles—those particles that, once lifted from the bed, have such small settling velocities that they remain suspended above the bed for long periods.

Answer 40

suspension load

Question 41

Water also transports a _that consists of the dissolved solids produced by the dissolution of rocks and minerals with which the water has been in contact.

Answer 41

solution load

Question 42

two major types of aqueous flow are recognized in sedimentary environments:

Answer 42

Unidirectional flows.
Oscillatory flows.

Question 43

are characterized by flow in one direction over a period of time.

Answer 43

Unidirectional flows

Question 44

A qualitative measure of the speed of a fluid flow, with different amounts of flow corresponding to different sedimentary structures, called bedforms.

Answer 44

Flow regime

Question 45

Two flow regimes are recognized:

Answer 45

The lower flow regime, where the bed is out of phase with the flow surface
The upper flow regime, where the bed is generally in phase with the flow surface

Question 46

Increasing transition of a lower flow regime

Answer 46

Stationary Flat Bed
Current Ripples (Straight Crested then to curved)
Sand waves/dunes on Bed

Question 47

Increasing transition of a upper flow regime

Answer 47

Plane Bed
Antidunes
Chutes and Pools

Question 48

Ripple Indices

Answer 48

Wavelength to Height ratio

Question 49

are straight-crested two-dimensional bed forms where, ideally, every two-dimensional cross-section parallel to flow is the same;

Answer 49

Sand waves

Question 50

are curved-crested three-dimensional bed forms where cross-sections parallel to flow vary.

Answer 50

dunes

Question 51

dunes begin to be sheared out into a flat or plane bed that is parallel to the nearly flat flow surface, marking the transition to lower to higher flow regime

Answer 51

plane bed or the plane bed transition.

Question 52

They migrate with the standing wave in an up-flow direction by lee-side erosion and stoss-side deposition.

Answer 52

antidunes

Question 53

Net aggradation of sediment on a flat or plane bed produces

Answer 53

horizontal stratification.

Question 54

sand waves and dunes do not form on what grain sizes

Answer 54

Coarse silt to fine sand

Question 55

sequence of bed forms for coarse silt to fine sand

Answer 55

(1) lower flow regime current ripples,
(2) upper flow regime plane bed transition, and
(3) antidunes.

Question 56

Current ripples do not form in beds composed of

Answer 56

coarse sand or gravel.

Question 57

sequence of bed forms for coarse sand or gravel.

Answer 57

(1) lower flow regime flat bed,
(2) sand waves or dunes,
(3) upper flow regime plane bed, and
(4) antidunes.

Question 58

troughs climb at angles equal the stoss-side slope.
the entire ripple form is preserved as sequences of lee-side cross-laminations

Answer 58

type I climbing ripple laminations.
Critically climbing ripples

Question 59

troughs climb at angles higher than the stoss-side slope angle
preserve both stoss-side and lee-side laminations and entire ripple forms

Answer 59

type II climbing ripple laminations
Supercritically climbing ripples

Question 60

“troughs climb at angles less the stoss-side slope.
only toe of foresets is preserved

Answer 60

Cosets of small scale ripple laminations
Subcritically climbing ripples

Question 61

As fallout from above increases from zero to extreme during the migration of ripple trains, the sequence of preserved structures evolves from:

Answer 61

(1) isolated ripple marks,
(2) horizontal laminations,
(3) small-scale cross-laminations,
(4) type I climbing ripple laminations, to
(5) type II climbing ripple laminations

Question 62

result from the erosion of preceding dunes by offset “scoop-shaped” troughs during bed aggradation.

Answer 62

Trough sets

Question 63

record the curvature of lee faces in cross-sections perpendicular to flow.

Answer 63

Festoon cross-strata

Question 64

Flow direction in festoon cross-strata

Answer 64

is roughly perpendicular to the place of maximum curvature in plan view (Figure 11.17).

Question 65

Waves moving through water whose depth is less than the wave base (< L/2) are called

Answer 65

transitional and/or shallow water waves.

Question 66

are straight-crested forms with small ripple indices (length: height ratios) produced by the back-and-forth movement of sand across the bed and across the ripple forms

Answer 66

Oscillation ripples

Question 67

is produced in protected areas with low sand : mud ratios and contains isolated lenses of ripple-laminated sand deposited from traction encased in dominant muds deposited from suspension

Answer 67

Lenticular stratification

Question 68

is characterized by subequal amounts of relatively continuous ripple-laminated sand and mud layers with the rippled sand giving the mud layers a wavy appearanc

Answer 68

Wavy stratification

Question 69

is produced in less protected areas with high sand : mud ratios.

Answer 69

Flaser stratification

Question 70

are thin mud drapes deposited from suspension that partially preserve ripple forms in areas dominated by the deposition of ripple-laminated sand

Answer 70

Flaser

Question 71

______________ characterized by gently inclined, convex-up cross-strata, whereas ________________is characterized by gently inclined, convex-down cross-strata, both in sets with thicknesses less than 0.5 m

Answer 71

hummocky cross stratification; swaley cross stratification

Question 72

where does HCS and SCS commonly occure

Answer 72

between the normal wave base and the storm wave base

Question 73

During major wind storms, the saltation load moves in part by _________ in which many saltating sand grains collide in mid-air, before reaching the bed, and stay suspended for longer than normal times.

Answer 73

sheet flow

Question 74

Larger grains are transported in a traction load by the process called _____, which is maintained by grain-to-grain collisions.

Answer 74

creep

Question 75

Coarse silt to medium sand is transported primarily by

Answer 75

saltation

Question 76

are transported slowly by creep in the traction load,

Answer 76

Fine to coarse sand and perhaps fine gravel

Question 77

repeated entrainment, transportation, and deposition produce a down-wind sequence from:

Answer 77

Coarse lag gravels
Well - Sorted sand deposits
Well-Sorted mud deposits

Question 78

examples of well sorted mud deposits caused by aeolian processes

Answer 78

poorly stratified loess deposits

Question 79

explain ripple indices

Answer 79

A measure of the symmetry of a ripple form, expressed by the ratio of ripple wavelength to ripple height.
Wavelenth / Height

Question 80

How does wind ripples differ from aqueous reipples

Answer 80

Wind ripples tend to have lower heights relative to wavelengths and thus larger ripple indices (RI > 12).
Wind ripples are strongly asymmetrical.
Unlike continuous-crested subaqueous current ripples, wind ripples show branching crests (Figure 11.29).

Question 81

are larger features (2.0 × 10² to 2.0 × 10⁴ m) composed of multiple dune forms with complex cross-stratification.

Answer 81

Dras

Question 82

Cold Dry Glacier vs Warm Wer glacier

Answer 82

Cold, dry glaciers occur in very cold regions where ice remains frozen most of the year.
processes involve flowing ice.
—
Warm, wet glaciers occur in regions that partially thaw for extended periods so that glacial ice is melted
mix of glacial ice flow and unidirectional aqueous flow.

Question 83

Glacial entrainment occurs primarily by some combination of three processes:

Answer 83

(1) erosion of unconsolidated sediment; (2) plucking; and (3) abrasion of bedrock.

Question 84

occurs when a glacier encounters an obstruction in an uneven bedrock surface, often where it is flowing downhill across bedrock.

Answer 84

Plucking

Question 85

In the glacial flow, what does Larger, medium, and small size particles in contact with bed rock produce,

Answer 85

Grooves, Strations, Polish

Question 86

Small particles entrained from glacier

Answer 86

rock flour

Question 87

No matter which set of depositional processes is involved, sediment deposited directly from glaciers is called

Answer 87

glacial till

Question 88

poorply sorted, boulder bearing and polymictic lithified glacial tills

Answer 88

tillites

Question 89

When icebergs melt, ice-rafted debris sinks to the bottom.
Large clasts dropped from icebergs are called

Answer 89

dropstones.

Question 90

are characterized by large proportions of sedimentary particles (≥ 80%) relative to water (≤ 20%), though they may contain significant air.

Answer 90

Granular flows

Question 91

are characterized by smaller amounts of sedimentary particles (∼ 60–80%) and larger amounts of liquid (∼ 20–40%) and are sometimes called liquefied flows.

Answer 91

Slurry flows

Question 92

possess lower sediment (∼ 20–60%) to water (∼ 40–80%) ratios and include hyperconcentrated stream flows and many, but not all, subaqueous turbidity currents.

Answer 92

Hyperconcentrated flows

Question 93

sediment concentration that separates high concentration and low concentration turbiditiry currents;
locations

Answer 93

> 60%; <20%
Proximal; Distal