Introduction to Geology Midterm 2 flashcards |

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(L9) Most clastic rocks are composed of?

-Clay minerals

(L9) Define Angularity, Sphericity, Sorting and Cement type?

-Angularity - how rounded a clast is / how
angular a clast is
-Sphericity - how equidimensional a clast is
(how near to a sphere shape)
-Sorting is the uniformity of grain size
-Cement type is what mineral fills the pores
between clasts

(L9) What kind of Clastic Rock is
-Grain size = Very coarse to coarse (>2mm)
-Angular clasts?

-Size and angularity => deposited close to source
(little transport)

(L9) What kind of Clastic Rock is
- Grain size = Very coarse to coarse (>2mm)
- Rounded clasts

-Clasts rounded during transport (farther from source)
-Large clasts = high velocity; e.g. fast moving river channel

(L9) What kind of Clastic Rock is
-Grain size = coarse to medium
-Sand- and small pebble-sized clasts with abundant feldspar
-Angular clasts common (cleavage)

ARKOSE (aka Feldspathic Sandstone)
-Feldspar = short transport (close to source)
-Moderate to low weathering = arid climate

(L9) What kind of Clastic Rock is
-Grain size = medium (visible to naked eye & up to 2mm)
-Sand-sized clasts; rounded clasts

-Quartz = most common mineral grain in sandstone
-Grains rounded during transport (fracture)
-Beach (water) or dune (wind) deposits

(L9) What kind of Clastic Rock is
-Grain size = fine to very fine (not visible to naked eye)
-Silt- and clay-sized clasts

- Mostly composed of clay minerals and minor quartz
- Shale is fissile (splits into thin layers); Silt/claystone not fissile
- A.k.a "mudstones" or "mudrocks"
- Calm water deposition (lake, deeper ocean)

(L9) Explain Shale?

- May contain fossils
- Fine sediment =
fine detail
- Calm water = low
- Calm water = less

(L9) The Three Categories of sedimentary

- Terrestrial (a.k.a. Continental) like Clastic Rocks
- Coastal (a.k.a. Transitional)
- Marine

(L9) Terrestrial Sedimentary Environments include?

Glaciers, High mountain streams, alluvial ice, desert, river"fluvial" and Lakes

(L9) Describe the Coastal Depositional Environments?

Transitional zone from terrestrial to marine

(L9) Explain Sedimentary Basins?

-Thick accumulations of sediment only
occur in certain places
-Surface of lithosphere sinks
-Room to collect sediments

(L9) explain Rift Basin, Passive Margin Basin and Foreland Basin?

- Rift Basin - thinning of crust; low area
- Passive Margin Basin - thinned crust at edge
of ocean basin
- Foreland Basin- mountain-building causes

(L10) Define Transgression?

-A rise in sea level
-Deep-water sediments end up above shallow-water

(L10)Define regression?

-A rise in seal level
-Shallow-water sediments end up above deep-water sediments

(L10) Explain Diagenesis?

-All of the chemical, physical and biological
processes that:
-Transform sediment into sedimentary rock, and...-Alter the characteristics of the sedimentary rock
after it is formed

(L10) Explain Metamorphism?

-Rocks don't stay the same forever!
-Meta = change Morph = form or shape
-Metamorphism - altering rocks by changing:
1) Pressure (P)
2) Temperature (T)
3) Chemical conditions
-Rock that changes = protolith or parent rock

(L10) Define Metamorphism?

Protolith undergoes a solid state change
as a result of a change in its environment
1) Solid state - no melting
2) Change - minerals (not in protolith)
and/or texture change (different from
3) Change in environment - change in T and/or
P; reactions with hydrothermal fluids

(L10) 4 Controlling Factors -
that affect final metamorphic rock produced?

-Composition of parent rock
-Temperature (T) - heat
-Pressure (P) - uniform or differential
-Hot fluids (chemically active)

(L10)Uniform Stress vs Differential Stress?

Uniform Stress:
-Retains features of protolith
-Non-foliated rocks
-Deep burial
Differential Stress:
-Deformation of bedding or
other features of protolith
-Foliated rocks
-Plate collision

(L10 The three types of directed pressure?


(L10) Define Contact metamorphism?

-Aka thermal metamorphism (heat from magma)
-Affects rocks surrounding an igneous intrusion =>
cool wall rock is metamorphosed
-Contact aureole
-No increase in P => forms non-foliated rocks
-Anywhere magma is generated

(L10) Define Burial metamorphism?

-Occurs in deep sedimentary basins (subsiding)
-Rocks become more dense, but not deformed
-Depth for burial metamorphism varies
(geothermal gradient varies from place to place)
-Usually occurs b/w 8 -15 km depth (200-400ยฐC)

(L10) Define Regional metamorphism?

-Produces most metamorphic rocks => large areas
-Associated with mountain building at convergent
plate boundaries
-Continental collisions most intense =>
metamorphic core in mountain range
-High P => foliated rocks

(L10) Define Hydrothermal metamorphism?

-Hydrothermal fluid (hot water) reacts chemically
with country rock
-Addition of water changes minerals to forms
-Source of hydrothermal fluids:Surface water, Regional metamorphic
reactions, Magma

(L10) Define Shock metamorphism?

-Meteor Impacts
-Extreme compression (shock wave)
-Causes phase change - more compact, dense
mineral phase
-Quartz => coesite or stishovite (shocked quartz)
-Also caused by nuclear explosions

(L10) Two types of metamorphic rocks classification?

-Parallel alignment of platy/elongate
-Presence of bands of light/dark minerals

Non-foliated (a.k.a. Massive)
-Mineral crystals have random orientation
-Often single mineral (mono-mineralic)

(L10) Three Non-Foliated metamorphic Rocks?

Marble, Quartzite and Hornfels

(L10) Four Foliated metamorphic Rocks?

Slate, Phyllite, Schist and Gneiss

(L11) Explain the Rock Cycle?

Rock is not permanent
-Weathering breaks down rock
-Melting destroys rock
changes rock
-Ongoing change from
one rock type to

(L11) What are the steps of the rock cycle?

Igneous Rock to Sedimentary Rock to metamorphic Rock and repeat

(L11) What is an Earthquake? and what is its cause?

- An episode of ground shaking
-What causes Earthquakes?
-Almost all significant earthquakes are
caused by:
1) Formation of a fault
2) Sudden movement along an existing fault

(L11) What is a fault?

-A fracture or break in the Earth's crust along
which movement occurs
-No movement => not a fault (just a fracture)

(L11) Explain the formation of a fault?

Rock bends, then breaks
-Vibrations =>
More sudden movement
on fault
-Vibrations =>
Vibrations due to
earthquake activity:
-Seismic activity or

(L11) Define the Hypercenter and Epicener?

Place within Earth where rock moves (vibrations
-Hypocenter or focus of the earthquake

Point on surface of Earth directly above focus:

(L11) Define Normal Fault?

the result of extension
-Hanging wall block (above fault) moves down
-Footwall block (below fault) moves up
>Relative motion

(L11) Define Reverse Fault?

the result of compression
-Hanging wall block (above fault) moves up
-Footwall block (below fault) moves down
>Relative motion

(L11) Define Thrust Fault?

low-angle reverse fault
-Hanging wall block (above fault) moves up
-Footwall block (below fault) moves down
>45ยฐ or less from horizontal down to fault plane

(L11) Define Slip-Strike Fault?

Strike-slip Fault - horizontal displacement
-No hanging wall or footwall block
>Tend to be vertical or near-vertical

(L11) Define Friction?

-faults don't slip forever; friction will
slow and stop movement; friction is
resistance to sliding on a surface

(L11) Define Main shocks and Aftershocks?

-Main earthquake (main shock) can be
followed by aftershocks, which are much
less powerful.
-Aftershocks are due to small movements
along to fault as the rocks on either side
adjust to their position ( stresses
may be placed on the rocks in there

(L12) Explain the Main shock and after shock?

Main earthquake is called the main shock:
-May be followed by aftershocks
-Much less powerful
-Due to small movements along to fault
-Rocks on either side adjust to their
position/ stresses

(L12) Energy that Travels through rock/sediment in the
form of waves known as? and how are they classified?

-Seismic Waves
Classified by:
-Where they move (through or along the Earth's surface
-How they move (compressional wave, or shear wave)

(L12) Where do body waves, and surface waves travel?

-Body waves(through interior of Earth)
-Surface waves (along the surface of the Earth)

(L12) How do Compressional and shear waves move?

-Compressional Waves(Movement is parallel direction wave is travelling
-Shear waves (movement is perpendicular wave is traveling

(L12) Difference between the L wave and the R wave?

They are both surface waves but the L-wave travels side-side while the R-Wave travels up and down

(L12) How are Earthquakes Measured?

Seismometer - instrument that measures ground
motion from an earthquake
Seismogram - record produced by seismometer
-Time on horizontal axis
-Wave amplitude (height) on vertical axis

(L12)How are Earthquakes Located?

using the Use difference in arrival time of the P and S waves to find the epicenter

(L12) Explain the Earthquakes Intensity?

-Intensity is subjective
-Varies with distance from the epicenter

(L12) Explain the magnitude of the Earthquake?

-Magnitude = maximum amplitude of
ground motion
-Measured by a seismometer at a standard distance
from the epicenter
-Magnitude doesn't vary with distance (standardized

(L13) Define Deformation?

flowing of rock in response to stress (apply a

(L13) Types of deformation?

-Joints: fractures in crust with NO displacement
between rock on either side of the crack
-Faults: fractures in crust with a distinct offset
(displacement) between the two sides
-Folds: rocks may be bent into a series of wavelike
-Foliations: layering due to mineral or grain
flattening and/or alignment (tectonic foliation)

(L13) Deformation results in one or more of
the following?

-Displacement - change in location
-Rotation - change in orientation
-Distortion - change in shape

(L13) Explain Compressional Stress?

-Shortening or contracting
-Object is squeezed
-Collision zones
-Crust is shortened and thickened

(L13) Explain Tensional Stress?

-Stretching or elongating
-Object is pulled apart
-Rift zones
-Crust is stretched and thinned

(L13) Explain Shear Stress?

-Surfaces slide past one another

(L13) Brittle vs. Ductile Deformation?

-Brittle deformation: rock breaks by
-Ductile deformation - change shape without
visible breaking; rocks flow and fold (solid state)

(L13) Explain the Rock behaviour factors? (temp and preasure)

-Temperature - heat makes materials softer
-Warmer rocks - ductile deformation
-Cooler rocks - brittle deformation
-Pressure - pressure prevents rocks from fragmenting
-Lower pressure - brittle deformation
-P and T increase with depth
-Crust rocks generally brittle

(L13) Explain the Rock behaviour factors? (composition)

-Composition - some rock types/minerals
softer than others
-Some minerals very brittle: quartz,
-Some minerals more ductile: halite, mica,
calcite, clay minerals

(L13)Explain the Rock behaviour factors? (rate of deformation)

-Rate of Deformation
-Rapid application of stress
-sudden change in shape causes
brittle defromation
-Small amounts of stress over long
geologic time
-slow change in shape causes ductile deformation => atomic and molecular
bonds have time to accommodate stress

(L13) characteristics of brittle structures?


(L13) Describe the type of ductile structure folds?

-Anticline (a up fold, shaped like an "A"
-Syncline (a down fold, shapes like a trough or a sink)
-Dome (an over-turned bowl, sedimentary layers get pushed up)
-Basin (an upright bowl, sedimentary layers subside)
-Monocline (an step-like fold, often draped over and underlying fault)

(L13) What processes that form folds?

-Thrust-faulting - rock
layers in hanging wall
bend as it is pushed up
and over footwall
-Faulting at depth -
overlying rock layers
bend into a monocline

(L14) Define Orogenesis?

-The process of Mountain Formation driven by plate tectonics
- This process happens to due the deformation of,Subduction zones, Continental collisions zones, and Continental rifts

(L14)Explain Subduction Orogenesis?

-Mini collisions (too buoyant
to subduct)
-Terrane becomes sutured/
welded to continent

(L14)Expliain Collision Orogenesis?

-Intense compression
-Folding and faulting
-Metamorphism (tectonic foliation)
-Crustal thickening
-Fold-thrust belts develop on both sides of
collision zone

(L14) Explain Rift Orogenesis?

-Stretching causes crustal thinning and normal
-Fault-block mountains
-Volcanic mountains due to decompression melting

(L14) Explain Mountain Topography and Uplift?

-Topography = the surface features of an area
(natural and man-made)
-Their position and elevation
-Features can be shown on a topographic map
-Uplift is the creation of topography by raising the surface of the earth to a higher elevation

(L14) Explain Isostacy?

-Isostacy = equilibrium in the Earth's crust
-Forces tending to elevate landmasses balance
forces tending to depress landmasses

(L14) Explain Fossils and paleontology?

-the remnants or traces (impressions)
of ancient living organisms, now preserved in
- Paleontology is the study of fossils (and ancient life)

(L14) Why are most fossils found in sedimentary rocks?

-Organisms die and are buried by sediment
-Organisms travel over or through sediment and leave

(L14) Steps in fossilization?

-Creature dies, leaving behind body and/or footprints
-Flesh rots away; bones and prints remain
-Bones/prints covered by sediment
-Sediment lithifies
-Minerals in groundwater replace bone
-Bones become rock-like (fossilize)
-Uplift and erosion exposes fossils

(L14) Type Of Fossils?

- Body Fossils(whole bodies preserved)
-Preserved or replaced bones/teeth/shells
-Molds(Hole left behind in
rock when shell is
dissolved away) and casts (Mold filled by sediment
that is lithified)
-Carbonized impressions
-Trace Fossils

(L14) Macro Vs Micro Fossils?

-While macro fossils can be seen with the naked eye, microfossils can't

(L14) Conditions required of fossilization?

One of either
-Oxygen Poor
-Rapid Burial
-Presence of hard parts

(L15) Three domains of a fossils life?


(L15) Explain Evolution?

-Changes over many generations is evolution
-Offspring can differ from their parents and
traits can be passed down to future generations
-Many changes can accumulate over many

(L15) Why does evolution occur?

-Beneficial characteristics are passed onto each
generation => Natural Selection
-Only organisms capable of surviving and
reproducing can pass on their genes to
successive generations
-In each generation, some individuals have
characteristics that make them more "fit"

(L15) Define gradualism and punctuated equilibrium?

-Gradualism : idea that evolution occurs at a
constant, slow rate
-Punctuated equilibrium : evolution occurs slowly at
some times, then rapidly at others

(L15) Causes for pulses of evolution?

1) Geologic catastrophe => many species go extinct; ecological
niche for species
2) Sudden climate change => organisms are put under stress; they
evolve to survive or go extinct
3) Formation of environments => e.g. rifting splits a
continent, creating ocean and coastlines
4) Isolation of a particular population => event that cuts off part
of a population from the rest

(L15) Reasons for extinction?

-Loss of habitat
-Disruption of food supply
-appearance of predator and competitor?
-if species can't adapt they'll die out

(L15) Explain Stenos Law of Original Horizontality?

-Sediments settle out of a fluid due to gravity
-Sediments accumulate horizontally (parallel to
surface of the Earth)
-Thus, tilted sedimentary rocks must be

(L15)Explain Stenos Law of Superposition?

-In an undeformed sequence of layered rocks:
-Each layer is older than the one above it
-Each layer is younger than the one below it

(L15)Explain Stenos Law of Lateral Continuity?

-Sedimentary strata often form laterally extensive
horizontal sheets
-Sediments tend to be deposited over large areas
-Erosion can dissect once-continuous layers

(L15) Define the principle of Uniformitarianism?

-"The present is the key to the past"
-Processes we see today also occurred in the past,at about the same rate
-These processes responsible for features we see preserved in rocks

(L15) Define the Principle of Cross-Cutting

-Younger geologic features cut or truncate older geologic features
-Examples: dikes, faults, erosional surfaces

(L15) Define the Principle of Inclusions?

-Inclusions are always older than the enclosing
-Weathered clasts

(L15) Define the Principle of Baked Contacts?

-An igneous intrusion metamorphoses (bakes) the
country rock it intrudes into
-The country rock is older than the intrusion
-The metamorphic "rind" is younger than the
country rock

(L15) What are the 5 Fundamental Geologic Events?

-Deposition of sedimentary beds
-Erosion of the land surface
-Intrusion/extrusion of igneous rocks
-Deformation (folding/faulting)
-Episode of metamorphism
(Can happen in ANY order!)

(L15) Explain the Principle of Fossil Succession?

-Fossils are generally preserved in sedimentary rocks
-Certain species lived at certain times in Earth's past
-Fossils found in a rock unit is the fossil assemblage
-As we go up, rocks (and fossil species)
become younger (superposition)
-99.9% of all species that ever lived areextinct

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