Grain Size

Question 1

• A widely used grade scale for expressing particle size
• A logarithmic and geometric scale with a fix ratio between successive elements

Answer 1

Udden-Wentworth Scale

Question 2

Udden-Wentworth Scale extends from

Answer 2

< 1/256 mm to >256 mm

Question 3

logarithmic scale for sediment size

Answer 3

Kumbrein Phi Scale

Question 4

Increase in abs value negative phi =

Answer 4

Increase in mm size

Question 5

• Increase in positive phi =

Answer 5

decrease in mm size

Question 6

particles that are settling will pass through a diffracted light, the angle of the diffracted light increases with a decreasing particle size. A detector senses the angular distribution of scattered light energy.

Answer 6

• Laser Diffraction size analyzer

Question 7

sediments are slowly poured into an electrolyte solution, where sediments will pass through, where changes in the electrical field will produce pulses, translating into the grain size

Answer 7

• Electro-resistant size analysers

Question 8

Φ < 0.35

Answer 8

VW Sorted

Question 9

0.35 < Φ < 0.5

Answer 9

W Sorted

Question 10

0.5 < Φ < 0.7

Answer 10

MW Sorted

Question 11

0.7 < Φ < 1

Answer 11

M Sorted

Question 12

1 < Φ <2

Answer 12

P Sorted

Question 13

2 < Φ <4

Answer 13

VP Sorted

Question 14

0.4 > Φ

Answer 14

EP Sorted

Question 15

• based on a constant ratio of two between successive class boundaries together with terms for the classes
• A Geometric Scale

Answer 15

Udden Wentworth Scale

Question 16

Kumbrein introduced an ?? Measured in ?? uunits

Answer 16

Kumbrein; Phi

Question 17

clast size of conglomerates and breccias can be measured directly with a ?

Answer 17

tape measure

Question 18

With poorly cemented sandstones and unconsolidated sands, ???is the most popular technique

Answer 18

sieving

Question 19

• Medium silt to small pebble
  
  • ?? min sieving time
  • ?? gram samples

Answer 19

15; 30

Question 20

show the frequency of grains in each size-class and usefully give an immediate impression of the grain-size distribution

Answer 20

histogram, smoothed frequency curve

Question 21

shows the percentage frequency of grains coarser than a particular value

Answer 21

cumulative frequency curve

Question 22

Most sediments are ??, i.e. one class dominate

Answer 22

Unimodal

Question 23

If grain-size distribution is perfectly normal

Answer 23

then the median, mean and mode values are the same

Question 24

grain size decreasing away from the source area

Answer 24

• relates to selective sediment transport
• fluvial and deltaic
• turbidites in deep-sea basin
• offshores, wave and current energy decrease

Question 25

a measure of the *standard deviation,* spread of the grain-size distribution.

Answer 25

- **Sorting**

Question 26

Several Factors that Determine Sediment Sorting

Answer 26

Sediment Source Grain Depositional Mechanism

Question 27

A general rule about sorting

Answer 27

improves along the sediment transport path

Question 28

a measure of the *symmetry of the distribution*

Answer 28

- **Skewness**

Question 29

If the distribution has a *????,* i.e. *excess coarse material,* then the sediment is said to be *????*

Answer 29

Coarse tail; Negatively Skewed

Question 30

If the distribution has a *????,* i.e. *excess fine material,* then the sediment is said to be *????*

Answer 30

Fine tail; Positively Skewed

Question 31

If the distribution is **symmetrical**, then there is **?????.**

Answer 31

no skew

Question 32

Skewness > 0.30

Answer 32

S fine skewed

Question 33

Skewness 0.3>0.1

Answer 33

fine skewed

Question 34

Skewness 0.1>--0.10

Answer 34

Near-symmetrical

Question 35

Skewness -0.1>--0.30

Answer 35

Coarse Skew

Question 36

Skewness >-0.30

Answer 36

S Coarse Skew

Question 37

*River sands* are usually *????* skewed

Answer 37

positive

Question 38

*Beach sands*, for example, tend to have a *???* skew

Answer 38

negative

Question 39

n general, sediment becomes more *????* skewed (and finer grained) along its *?????/*

Answer 39

Negative; Sediment Transport Path

Question 40

????????? becomes more *positively skewed* and relatively coarse

Answer 40

source sediment (lag?

Question 41

- section diameter of **randomly oriented grains** are usually **smaller** than their **maximum diameter** - grains cut marginally in a thin-section plane have smaller apparent diameters

Answer 41

Corpuscle Effect

Question 42

- sharpness or peakedness of a grain-size frequency curve

Answer 42

Kurtosis

Question 43

- **Sharp peaked** curves - **better sorting** in the **central** portion of the grain-size distribution

Answer 43

Leptokurtic

Question 44

- **flat peaked** curves - **poor sorting** in the **central** portion of the grain-size distribution

Answer 44

Playkurtic

Question 45

A method of direct calculation of mean size, std dev, skewness, kurtosis w/o cumulative curve plots

Answer 45

Moment Method

Question 46

- when size distribution of natural sediment, such as dune sand, is plotted on **log–log plots** and a **curve is fitted** to these data, the resulting curve actually has the shape of a **??????**

Answer 46

hyperbola