lithology in photos Flashcards
2 general criteria for rock type identification based on photographic appearance
climate and amount of relief
what are the 4 criteria you need to follow for lithology identification
- determine climatic environment and associate type of erosional environment
- recognize and mark bedding traces of sediments / mark outline of outcrop
- recognize and mark areas of superficial cover that do not indicate bedding, fold and determine the position of the axial traces
- study lineament whether they represent faults dykes or joints
types of climatic environment
desert, arid, semiarid, humid, temperate, tropical
describe general characteristics of intrusive igneous rocks
- massive
- isotropic
- homogeneous
- cross-cutting relations with country rocks
- has different shapes and dimensions
in humid regions, what is characteristic for intrusive igneous rocks
hummocky or rounded dome like topography
what is the characteristic drainage pattern for intrusive igneous rocks (unless structural controlled)
dentritic or radial-annular (or rectilinear)
describe vegetation in intrusive igneous rocks
uniform more or less
what is the tone for acidic intrusives
light and uniform tone
what is the tone for basic intrusives
dark to black
what are the associated landforms of extrusive igneous rocks
lavaflows, cones, craters, plug, volcanic necks, flat topped plateaus
describe the flow structure of extrusive igneous rocks
successive
describe the surface feature of extrusive igneous rocks
rough and irregular terrace surfaces
describe the pattern of vegetation and topography in extrusive igneous rocks
lobate patterns
differentiate extrusive igneous rocks in arid and humid regions
arid - sparse
humid - luxuriant
drainage pattern for extrusive igneous rocks
dentritic or radial
describe the tone for acidic extrusives
light and uniform
describe the tone for basic extrusives
dark to black
describe erosion rate for extrusive igneous rocks
active
T or F. columnar joints are common in extrusive igneous rocks
T
describe the composition, weathering, tone, drainage, topography, vegetation and joints for granite
composition: acidic intrusives
weathering: variable
tone: bright
drainage: low to med density dendritic
topography: low lying
vegetation: variable
joints: 3 or 4 set
describe the composition, weathering, tone, drainage, topography, vegetation and joints for rhyolite/pumice/obsidian
composition: acidic extrusive
weathering: highly susceptible
tone: bright
drainage: radial
topography: rough and irregular
vegetation: poor
joints: faintly developed
describe the composition, weathering, tone, drainage, topography, vegetation and joints for dolerite
composition: basic intrusive
weathering: basic dykes are susceptible
tone: dark
drainage: none
topography: linear ridge or depression
vegetation: absent
joints: present
describe the composition, weathering, tone, drainage, topography, vegetation and joints for basalt
composition: basic extrusive
weathering: highly susceptible
tone: dark
drainage: fine dendritic
topography: flat and rough
vegetation: sparse
joints: columnar
describe the composition, weathering, tone, drainage, topography, vegetation and joints for gabbro/peridotite
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
granite landforms
rounded outcrops or residual hills
rhyolite/pumice/obsidian landforms
oblate in outline, volcanic landform
dolerite landforms
as wall or trench. sills like sheets
basalt landforms
flow structures with oblate lining
gabbro/peridotite landforms
small dimension plugs and domes
T or F. it is easy to identify metamorphic rocks in aerial photos
F. difficult
instead of bedding, what are structural trends in metamorphic rocks
foliations
what do parallel alignments of ridges imply?
regional cleavage, foliation or fold axis = metamorphic rocks
what do lineations in metamorphic rocks represent
regional cross-joints, may be reflected in abrupt deflections of drainage along straight stream segments
the most prominent feature in sedimentary rocks
bedding
how do sedimentary rocks look like in aerial photos because of differential weathering
banded patterns
explain how banding can be used to mark beds in absence of topographic expressions for sedimentary rocks
banding due to vegetation or soil differences express different topographic tone
what part of the geomorphic cycle is bedding most prominent
mature stage
