course outcome 2 Flashcards
materials of the earth
naturally
occurring, coherent
aggregates of either/and
Minerals
Glass
Organic Material
rocks
means that a rock
must be held together and is
not broken into pieces. Thus,
a pile of minerals is not rock.
coherent
A classification of formative processes,
and a correlation of these processes
with the rock types and the intrinsic
characteristics of which they have
developed.
genetic scheme
shows how
one type of rocky material
gets transformed into
another.
Representation of how
rocks are formed,
broken down, and
processed in response
to changing conditions
Processes may involve
interactions of
geosphere with
hydrosphere,
atmosphere and/or
biosphere.
rock cycle
blank is created by the
melting of rock at a convergent boundary or subduction
zone.
magma
Less dense magma rises and cools to form?
igneous rock
Igneous rock exposed at surface gets weathered into
sediment
Sediments transported to low – lying areas, buried
and hardened into
sedimentary rock
Sedimentary rock heated and squeezed at depth to
form
metamorphic rock
Metamorphic rock may heat up and melt at depth to
form?
magma
igneous processes
melting and crystallization
sedimentary processes
weathering and erosion
extrusive and intrusive
classification according to location (occurence)
metamorphic processes
burial (heat and pressure)
felsic, intermediate, mafic, ultramafic
classification according to composition (chemistry)
course-grained, fine-grained, porphyritic, glassy, vesicular, pyroclastic
classification according to texture (graining)
form when magma
solidifies underground
intrusive igneous rocks
form when magma
solidifies at the Earth’s
surface (lava)
extrusive igneous rocks
formed deep underground and typically cools
slowly.
intrusive
formed at or near the Earth’s surface and cools
quickly.
extrusive
the rock’s appearance concerning the size, shape,
and arrangement of grains or other constituents. The rate of
cooling of the magma determines crystal size
texture
mineral content indicates the
origin and evolution of the magma.
chemical composition
crystals are too small to see
easily with the naked eye. Magma cooled quickly at or near
the surface
fine-grained or APHANITIC
crystals are large enough
to see with the naked eye. Magma cooled slowly
coarse-grained or phaneritic
extremely coarse-grained (most crystals >5 cm), formed
when magma cools very slowly at depth
pegmatitic
includes two distinct crystal sizes, with the larger
phenocrysts forming first during slow cooling underground and the
smaller groundmass forming during more rapid cooling at the
Earth’s surface.
porphyritic
contains no crystals at all and is formed by extremely
rapid cooling of the magma
glassy
contains cavities (vesicles) in extrusive rocks resulting
from gas bubbles in the lava. Scoria and pumice are examples.
vesicular
consolidated
pyroclastic debris such as
ash, pumice, or crystalline
rock.
Examples: Tuff and
Volcanic Breccia
pyroclastic
Igneous rocks are mainly composed of?
silicate minerals
containing more silica, Na, K
(feldspars, quartz, muscovite)-
felsic
non-ferromagnesian minerals
containing more Ca, Fe, Mg
(olivine, pyroxene, amphibole,
biotite) - mafic
dark ferromagnesian minerals
Composed mostly of
non-ferromagnesian
minerals (Quartz and
feldspar) allowing the
rock to be light-
colored
Fel (Feldspar) + Sic
(Silicon)
>65% silica by weight,
and contains light-
colored minerals that
are abundant in silica,
aluminum, sodium,
and potassium.
Examples: Rhyolite
and Granite
felsic rocks
silica contents
between 55% and 65%
by weight. Diorite and
Andesite are examples
After the common
rock Andesite and they
have at least 25% dark
minerals thus being
between granitic and
basaltic in color.
Mainly composed of
amphibole, biotite, and
plagioclase feldspar
intermediate rocks
Substantial amount
of ferromagnesian
minerals leading to
dark-colored rocks
Ma (Magnesium) +
fic (Iron)
silica content
between 45% and 55%
by weight, contain
dark-colored minerals
that are abundant in
iron, magnesium and
calcium. Gabbro and
Basalt are examples.
mafic rocks
Melting occurs when rising
mantle rock is subject to lower
melting points as the pressure
is reduced.
decompression melting
the rate at which
temperature increases
with increasing depth
but it is never high
enough to cause rock
to melt because
melting points of
minerals generally
increase as pressure
increases.
Melting will occur by
a reduction in the
melting point by the
presence of water.
the geothermal gradient and partial melting
The composition of
peridotite and other
ultramafic rocks is
mostly olivine and
pyroxene
Almost entirely
composed of
ferromagnesian
minerals
<45% silica, by weight,
and composed almost
entirely of dark-colored
(black/green)
ferromagnesian
minerals.
Peridotite and Komatite
are examples.
ultramafic rocks
Water becomes increasingly
reactive at higher
temperatures.
At sufficient pressures and
temperatures, highly reactive
water vapor can reduce the
melting point of rocks by over
200°C.
flux melting / addition of water
the process by which
different ingredients separate from an
originally homogenous mixture.
differentiation
process by which
the magma composition varies as
different minerals/rocks melt at
different temperatures.
partial melting
changes the
magma composition as the crystals
are removed from the melt as they
settle downward. Also called as
Fractional Crystallization
Evolution of Magma: Crystallization
crystal settling
Minerals crystallize in a
predictable order, over a large temperature range
bowen’s reaction series
As mafic magma cools,
it initially crystallizes minerals like olivine,
followed by pyroxene, amphibole, and biotite.
These minerals are removed from the melt,
leaving the remaining magma enriched in silica
discontinuous branch
Plagioclase feldspar
evolves from calcium-rich (anorthite) to sodium-
rich (albite) compositions, gradually changing
the composition of the magma as it cools
continuous branch
the process where mantle-
derived magma incorporates material from
the Earth’s crust, influencing the composition
of the magma
contamination
process whereby a hot
magma composition will change as it
melts and assimilates adjacent rocks into
the magma.
assimilation
composition of a magma body
changes as it mixes with another magma body
magma mixing
Intrusive rocks exist in bodies or structures that
penetrate or cut through pre-existing country
rocks.
given names based on their
size, shape, and relationship to country rock.
intrusive bodies
Shallow intrusion formed when magma solidifies in
throat of volcano.
volcanic neck
Igneous bodies that apparently solidified near the surface of the
Earth.
Relatively small compared to bodies formed at great depth.
Tend to cool more rapidly than those that form at greater depth
and are likely fine-grained
shallow intrusive structures
Shallow, tabular intrusive
structure that cuts across any layering
in country rock
dike
Shallow, tabular intrusive structure
that parallels layering in country rock.
sill
deep, large,
blob-shaped intrusive
bodies formed of coarse-
grained igneous rock,
commonly granitic in
composition
plutons
small
plutons (exposed
<100km²)
stocks
large
plutons (exposed
>100km²)
batholiths
Most abundant rock in mountain ranges
and interior lowlands of continents.
granite
the predominant rocks of the
oceans
gabbro and basalt
the building material of young
mountain ranges.
andesite
Differentiation of mafic
magmas.
Partial melting of
oceanic crust.
origin of andesite
Rising mantle plumes can
produce localized
hotspots and volcanoes
when they produce
magmas that rise
through oceanic or
continental crust.
Hawaii is an example.
intraplate igneous activity
Partially melted lower
continental crust.
Magmatic
underplating.
origin of granite
landforms formed by the
extrusion of lava.
volcanoes
occurs when magma
makes its way to the Earth’s surface
volcanism
produces
rapidly cooled rock fragments called pyroclasts
explosive eruptions
produced when magma
reaches Earth’s surface
lava
size ranges from dust (ash)
to boulders (blocks and volcanic
bombs)
pyroclasts
Creation of New Land
Lava flows build up volcanic islands like Hawaii where
Kilauea volcano continuously erupted from 19 83-2018
Geothermal Energy
Underground heat generated by igneous activity
Effect on Climate
Very large eruptions can result in measurable global
cooling resulting in crop failures and famines
why should we study volcanoes?
calm oozing of
magma out of the ground produces
lava flows
effusive eruptions
low viscosity and flows easily
mafic lava flows
very low viscosity and flows very
easily from erupting fissures
flood basalts
parallel mostly six-sided vertical columns
columnar jointing
pillow structure formed as lava flows
into water.
submarine lava flows
thicker viscous lavas that
flow short distances
intermediate and felsic lava flows
Dust, ash, cinders, lapilli,
blocks and bombs
pyroclastic materials
Mixture of gas and
pyroclastic debris that
flows rapidly down slope
pyroclastic flows
Small and steeply
sloping.
Composed of a pile of
loose cinders; basalt is
common.
cinder cones
Broad and gently sloping.
Composed of solidified basaltic lava flows.
Flows often contain lava tubes.
shield volcanoes
locations of major volcanoes
pacific ocean and mediterranean sea (ring of fire)
Moderately to steeply sloping.
Constructed of alternating layers of pyroclastic
debris and solidified lava flows.
Composed primarily of intermediate
composition volcanic rocks (for example,
andesite).
Most common type of volcano at convergent
plate boundaries.
Mainly located around the Pacific Ocean (Ring
of Fire) and Mediterranean Sea
composite volcanoes
extremely high
viscosity, degassed,
felsic lavas (often glassy,
for example, obsidian)
lava domes
volcanic
depression at least 1
km in diameter
Result from very
violent eruptions.
Crater Lake in
Oregon is an
example.
calderas
Pyroclastic flows – account for
the largest number of deadly
events – Pompeii.
Volcanic gases – carbon
dioxide, Nyos Cameroon.
Volcanic mudflows (Lahars),
Armero Colombia.
Indirect hazards such as
famine and lightning.
Eruption times correspond
with largest mass extinction
events
volcanic hazards
if currently or recently eruptive
(Approximately 500 in the world today)
active volcanoes
if it hasn’t erupted in many
thousands of years but is expected to
erupt in the future.
dormant volcanoes
Decompression Melting.
Effusive eruptions of basaltic magmas and pillow lavas.
Formation of most of the sea floor.
Mid-oceanic ridges, Iceland
volcanic activity at divergent boundaries
haven’t erupted in many years
and show no signs of any future
eruptions.
extinct volcanoes
Most large well – known volcanoes.
Explosive composite volcanoes.
Viscous andesitic lavas
volcanic activity at convergent boundaries
Mantle Plumes (Hot Spots) – Hawaii, Yellowstone.
Basaltic magma/lava.
within-plate volcanic activity
the group of
destructive processes that
change physical and
chemical character of rocks
at or near Earth’s surface
weathering
physical picking up
of rock particles by water, ice,
or wind
erosion
the
movement of eroded
particles by water, ice, or
wind
transportation
processes
that break rocks into smaller pieces
without changes to the chemical
composition
mechanical weathering
decomposition of rock from exposure
to water and atmospheric gases
(carbon dioxide, oxygen and water
vapor)
chemical weathering
Destruction of building materials
Discoloration of surface outcrops
Production of soil
Impacts the atmosphere
Removes carbon dioxide
Creates interesting and unusual rock
shapes
Spheroidal weathering
Differential weathering
effects of weathering
Rocks weather at different rates
Example: shale (composed of soft clay minerals) tends to
weather and erode faster than sandstone (made of hard quartz
minerals)
differential weathering
mechanic effect
of freezing (and expanding)
water on rocks. Frost wedging
and frost heaving
frost action
removal of overlying
rock allows expansion and fracturing.
Exfoliation domes
pressure release
Plant growth – growing roots widen fractures
Burrowing animals
Thermal Variation – large temperature changes fracture rocks by
repeated expansion and contraction
Salt pressure
other types of mechanical weathering
chemically active oxygen from
atmosphere
Iron oxide stains are common
result.
role of oxygen in chemical weathering
hydrogen cations
replace others in minerals
Carbonic acid from atmospheric C
O₂ dissolved in water.
Sulfuric, hydrofluoric acids emitted
by volcanic eruptions.
Some minerals, such as calcite,
may be totally dissolved.
Human activity, such as mining
and burning of fossil fuels,
produces acids.
role of acids in chemical weathering
most common
minerals in crust
Slightly acidic rainwater attacks
feldspar
clay minerals produced
chemical weathering of feldspars
Similar to feldspars, creates clay
minerals and dissolved ions.
More complex silicate bonds
lead to lower weathering
susceptibility.
Chemical weathering of other minerals
availability of water
climate
rock composition
slope
factors affecting weathering
a layer of
weathered,
unconsolidated
material on top of
bedrock
common soil
constituents:
Clay minerals
Organic matter
Water
Quartz
soil
uppermost layer; organic material
O horizons
dark-colored, rich in organic matter and high
in biological activity
A horizons
zone of accumulation; clays and iron oxides
leached down from above; formation of hard pan in wet
climates
B horizon
zone of leaching; fine-grained material
removed by percolating water
E horizon
parent material
slope
living organisms
climate
time
factors affecting soil formation
partially weathered bedrock
C Horizon
The O and A horizons are the most valuable and the most
vulnerable to erosion.
How Soil Erodes:
Soil particles are small and are therefore easily eroded (carried
away) by water and wind.
Water erosion is the most significant type; wind erosion is generally
less significant.
Rates of Erosion:
Soil characteristics, climate, slope, vegetation.
Consequences of Erosion:
Removal of an essential resource.
Sedimentation of water bodies.
soil erosion
gray to brown surface horizon, common
in humid forests
alfisols
soils formed in volcanic ash
andisols
soils formed in dry climates (low
organic matter)
aridisols
young soils that have no horizons
entisols
wet, organic soils with little mineral
material.
histosols
weakly weathered soils with
permafrost within 2 meters of the surface
gelisols
very young soils with weakly
developed soil horizons
inceptisols
nearly black surface horizon rich in
organic matter.
mollisols
heavily weathered soils (also called
laterites)
oxisols
acid soils low in plant nutrient ions
spodosols
clay soils that swell when wet and
shrink when dry
vertisols
strongly weathered soils low in plant
nutrient ions and clays
ultisols
produced from weathering
products of pre-existing rocks
or accumulated biological
matter
sedimentary rocks
rocks produced
from rock fragments
detrital rocks
rocks produced
by precipitation of
dissolved ions in water
chemical rocks
rocks produced by
accumulation of biological
debris, such as in swamps
or bogs.
organic rocks
loose, solid particles
originating from
weathering and erosion of pre-existing
rocks.
chemical precipitation from solution,
including secretion by organisms in
water.
Classified by particle size
Boulder – >256 mm.
Cobble – 64 to 256 mm.
Pebble – 2 to 64 mm.
Sand – 1/16 to 2 mm.
Silt – 1/256 to 1/16 mm.
Clay – <1/256 mm.
sediment
Movement of sediment away from its source, typically by
water, wind, or ice
Rounding of particles occurs due to abrasion during
transport.
Sorting occurs as sediment is separated according to
grain size by transport agents, especially running
water.
Sediment size decreases with increased transport
distance.
sediment transportation
Transported material settles and comes to a rest
Accumulation of chemical or organic sediments,
typically in water.
environment of deposition is the location in which
deposition occurs
Deep sea floor.
Beach.
Desert dunes.
River channel.
Lake bottom.
sediment desposition
Sediment must be preserved, as by burial with additional
sediments, in order to become a sedimentary rock
preservation
General term for processes converting loose sediment into
sedimentary rock.
Combination of compaction and cementation.
lithification
Most common.
Form from cemented sediment grains
that come from pre-existing rocks.
Chemical
Crystalline textures.
Form by precipitation of minerals from
solution.
detrital sedimentary rock
Breccia and Conglomerate
coarse – grained clastic sedimentary
rocks breccia composed of coarse,
angular rock fragments
conglomerate composed of rounded
gravel Sandstone
Medium – grained clastic sedimentary
rock types determined by composition
Quartz sandstone – >90% quartz grains.
Arkose – mostly feldspar and quartz
grains.
Graywacke – sand grains surrounded by
dark, fine-grained matrix, often clay – rich.
detrital rocks
Accumulate from remains of organisms
organic sedimentary rock
Contain C O₃ as part of their chemical
composition.
Most are biochemical, but can be
inorganic.
often contain easily recognizable
fossils.
Limestone is composed mainly of
calcite, Susceptible to recrystallization.
Dolomite chemical alteration of
limestone in Mg-rich water solutions
can produce dolomite.
Bioclastic limestones
carbonate rocks
fine-grained clastic sedimentary
rock; fissile (splits into thin layers)
Silt – and clay-sized grains.
Sediment deposited in lake bottoms,
river deltas, floodplains, and on deep
ocean floor.
Siltstone – slightly coarser-grained
than shale; non-fissile
Claystone – predominantly clay – sized
grains; non-fissile
Mudstone – silt – and clay – sized
grains; massive/blocky
fine-grained rocks shale
Hard, compact, fine-grained,
formed almost entirely of silica.
Can occur as layers or as lumpy
nodules within other sedimentary
rocks, especially limestone.
chert
Form from
evaporating saline
waters (lake, ocean).
Common examples
are rock gypsum, rock
salt.
evaporites
sedimentary rock
forming from compaction
of partially decayed plant
material
Organic material
deposited in water
with low oxygen
content (that is,
stagnant).
coal
Originate from organic matter in
marine sediment
Diatoms and single – celled algae
settle to sea floor
Oxygen poor waters preserve the
organic material
Higher temperatures convert
organics to oil and gas
Accumulates in porous overlying
rocks
oil and natural gas
Features within sedimentary rocks produced during or
just after sediment deposition
Provide clues to how and where deposition of
sediments occurred.
Bedding
Series of visible layers within a rock.
Most common sedimentary structure.
sedimentary structures
Series of thin, inclined
layers within a
horizontal bed of rock.
Common in
sandstones.
Indicative of
deposition in ripples,
bars, dunes, deltas.
cross-bedding
Small ridges formed on surface of
sediment layer by moving wind or
water
ripple marks
Polygonal cracks
formed in drying mud
mud cracks
Progressive change in grain size from
bottom to top of a bed.
graded bedding
Traces of plants or
animals preserved in
rock.
Hard parts (shells,
bones) more easily
preserved as fossils
fossils
A rock body of considerable thickness that is
large enough to be mapped.
Often based on rock type.
Must have a visible characteristic that makes it a
recognizable unit.
Given proper names such as the Anastasia Formation
or Ocala Limestone.
formation
a boundary surface between two different
rock types or ages of rock.
contact
location where sediment came to
rest
environment of depositional
sea level falls and the
sedimentary deposits will migrate
away from the land areas
regression
sea level rises and
marine sedimentary deposits will
migrate onto the subsided land
areas.
transgression
Plate movement is responsible
for the distribution of many
sedimentary rocks
Sedimentary rock distribution
often provides information that
helps geologists reconstruct
tectonic events
erosion rates and depositional
characteristics give clues to each
type of tectonic plate boundary
tectonic setting of sedimentary rocks
refers to solid-
state changes to rocks in Earth’s
interior
Produced by increased heat,
pressure, or the action of hot,
reactive fluids.
Old minerals, unstable under
new conditions, recrystallize
into stable ones.
Rocks produced from pre-
existing or parent rocks in this
way are called metamorphic
rocks
Metamorphic rocks common in
the old, stable cores of
continents, known as cratons
metamorphism
Texture and mineral content of metamorphic rocks depend
on:Parent rock composition.
Temperature and pressure during metamorphism.
Effects of tectonic forces.
Effects of fluids, such as water.
Parent rock composition
Usually no new material is added to rock during
metamorphism.
Resulting metamorphic rock will have similar composition
to parent rock.
metamorphic rocks
The heat for
metamorphism comes
from Earth’s deep
interior
All minerals stable over
finite temperature
range, if range
exceeded, new
minerals result.
If temperature gets
high enough, melting
will occur.
temperature
Metamorphism, particularly from high pressures, may take
millions of years.
Longer times allow newly stable minerals to grow larger
and increase foliation.
time
Confining pressure applied equally
in all directions.
Pressure proportional to depth
within the Earth.
High-pressure minerals more
compact/dense.
Differential Stress – created by
forces that are not equal in all
directions.
Compressive stress causes
flattening perpendicular to stress.
Shearing causes flattening by
sliding parallel to stress.
pressure
Planar rock texture of aligned minerals
produced by differential stress
Formed by differential stress.
foliation
Hot water (as vapor) is most important.
Rising temperature causes water to be released from
unstable minerals.
Hot water very reactive; acts as rapid transport agent for
mobile ions.
fluids
Foliated rocks are named based on the type of foliation (slaty, schistose,
gneissic)
foliated metamorphic rocks
Marble – coarse grained rock composed of interlocking calcite crystals.
Quartzite – produced when grains of quartz sandstone are welded together.
Hornfels – fine grained rock typically composed of microscopically visible micas
formed from the clay particle in shale
nonfoliated metamorphic rocks
occurs
when a body of magma comes
in contact with relatively cool
country rock
High temperature is
dominant factor.
Produces non-foliated
rocks.
Occurs in narrow zone (~1-
100 m wide) known as
contact aureole.
Rocks may be fine- (for
example, hornfels) or
coarse-grained (for
example, marble,
quartzite).
contact metamorphism
rocks precipitated from or
altered by hot water
Common at divergent plate
boundaries.
Hydrothermal processes:
Metamorphism.
Metasomatism.
Hydrothermal Processes
and Ore Deposits
Water passes through rocks
and precipitates new
minerals on walls of cracks
and in pore spaces.
Metallic ore deposits often
form this way (veins)
hydrothermal metamorphism
occurs
over wide areas and deep in the
crust
High pressure is dominant
factor.
Results in rocks with foliated
textures.
Prevalent in intensely
deformed mountain ranges.
May occur over wide
temperature range
regional metamorphism
produced by rapid
application of extreme
pressure
Meteor impacts
produce this.
Shocked rocks are
found around and
beneath impact
craters.
shock metamorphism
Minerals present in a metamorphic rock
indicate its metamorphic grade.
Prograde Metamorphism – as a rock is
buried to greater depths it is subject to
greater temperatures and pressures causing
recrystallization into higher grade rocks.
Slate → Phyllite → Schist → Gneiss → Lower
Grade → Higher Grade
Migmatites (partial melting) exhibit both
intrusive igneous and foliated metamorphic
textures
Pressure and Temperature Paths in Time
Index minerals can be used to
approximate temperature and pressure
conditions
metamorphic grade
Particularly important at mid –oceanic ridges as seas
water moves downward into cracks in the sea floor
Hydrothermal vents such as “black smokers” occur as
the water returns to the ocean
Dissolved metals and sulfur precipitate to create
mounds around the vents.
hydrothermal metamorphism and plate tectonics
can be used to approximate temperature and
pressure conditions
index minerals
Temperature varies
laterally at convergent
boundaries
Isotherms bow down
in sinking oceanic
plate and bow up
where magma rises.
Wide variety of
metamorphic facies.
pressure-temperature regimes
