lithology in photos

Question 1

2 general criteria for rock type identification based on photographic appearance

Answer 1

climate and amount of relief

Question 2

what are the 4 criteria you need to follow for lithology identification

Answer 2

1. determine climatic environment and associate type of erosional environment
2. recognize and mark bedding traces of sediments / mark outline of outcrop
3. recognize and mark areas of superficial cover that do not indicate bedding, fold and determine the position of the axial traces
4. study lineament whether they represent faults dykes or joints

Question 3

types of climatic environment

Answer 3

desert, arid, semiarid, humid, temperate, tropical

Question 4

describe general characteristics of intrusive igneous rocks

Answer 4

• massive
• isotropic
• homogeneous
• cross-cutting relations with country rocks
• has different shapes and dimensions

Question 5

in humid regions, what is characteristic for intrusive igneous rocks

Answer 5

hummocky or rounded dome like topography

Question 6

what is the characteristic drainage pattern for intrusive igneous rocks (unless structural controlled)

Answer 6

dentritic or radial-annular (or rectilinear)

Question 7

describe vegetation in intrusive igneous rocks

Answer 7

uniform more or less

Question 8

what is the tone for acidic intrusives

Answer 8

light and uniform tone

Question 9

what is the tone for basic intrusives

Answer 9

dark to black

Question 10

what are the associated landforms of extrusive igneous rocks

Answer 10

lavaflows, cones, craters, plug, volcanic necks, flat topped plateaus

Question 11

describe the flow structure of extrusive igneous rocks

Answer 11

successive

Question 12

describe the surface feature of extrusive igneous rocks

Answer 12

rough and irregular terrace surfaces

Question 13

describe the pattern of vegetation and topography in extrusive igneous rocks

Answer 13

lobate patterns

Question 14

differentiate extrusive igneous rocks in arid and humid regions

Answer 14

arid - sparse
humid - luxuriant

Question 15

drainage pattern for extrusive igneous rocks

Answer 15

dentritic or radial

Question 16

describe the tone for acidic extrusives

Answer 16

light and uniform

Question 17

describe the tone for basic extrusives

Answer 17

dark to black

Question 18

describe erosion rate for extrusive igneous rocks

Answer 18

active

Question 19

T or F. columnar joints are common in extrusive igneous rocks

Answer 19

T

Question 20

describe the composition, weathering, tone, drainage, topography, vegetation and joints for granite

Answer 20

composition: acidic intrusives
weathering: variable
tone: bright
drainage: low to med density dendritic
topography: low lying
vegetation: variable
joints: 3 or 4 set

Question 21

describe the composition, weathering, tone, drainage, topography, vegetation and joints for rhyolite/pumice/obsidian

Answer 21

composition: acidic extrusive
weathering: highly susceptible
tone: bright
drainage: radial
topography: rough and irregular
vegetation: poor
joints: faintly developed

Question 22

describe the composition, weathering, tone, drainage, topography, vegetation and joints for dolerite

Answer 22

composition: basic intrusive
weathering: basic dykes are susceptible
tone: dark
drainage: none
topography: linear ridge or depression
vegetation: absent
joints: present

Question 23

describe the composition, weathering, tone, drainage, topography, vegetation and joints for basalt

Answer 23

composition: basic extrusive
weathering: highly susceptible
tone: dark
drainage: fine dendritic
topography: flat and rough
vegetation: sparse
joints: columnar

Question 24

describe the composition, weathering, tone, drainage, topography, vegetation and joints for gabbro/peridotite

Answer 24

composition: basic and ultrabasic intrusive
weathering: highly susceptible
tone: dark
drainage: coarse/fine dendritic or radial
topography: undulating rolling or rough and jagged
vegetation: scanty
joints: well developed

Question 25

granite landforms

Answer 25

rounded outcrops or residual hills

Question 26

rhyolite/pumice/obsidian landforms

Answer 26

oblate in outline, volcanic landform

Question 27

dolerite landforms

Answer 27

as wall or trench. sills like sheets

Question 28

basalt landforms

Answer 28

flow structures with oblate lining

Question 29

gabbro/peridotite landforms

Answer 29

small dimension plugs and domes

Question 30

T or F. it is easy to identify metamorphic rocks in aerial photos

Answer 30

F. difficult

Question 31

instead of bedding, what are structural trends in metamorphic rocks

Answer 31

foliations

Question 32

what do parallel alignments of ridges imply?

Answer 32

regional cleavage, foliation or fold axis = metamorphic rocks

Question 33

what do lineations in metamorphic rocks represent

Answer 33

regional cross-joints, may be reflected in abrupt deflections of drainage along straight stream segments

Question 34

the most prominent feature in sedimentary rocks

Answer 34

bedding

Question 35

how do sedimentary rocks look like in aerial photos because of differential weathering

Answer 35

banded patterns

Question 36

explain how banding can be used to mark beds in absence of topographic expressions for sedimentary rocks

Answer 36

banding due to vegetation or soil differences express different topographic tone

Question 37

what part of the geomorphic cycle is bedding most prominent

Answer 37

mature stage