Exam #2 Flashcards
(130 cards)
1
Q
Atom
A
the smallest individual particle that retains distinctive properties of a given chemical element
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Q
4 major types of bonds
A
ionic, covalent, metallic, van der waals and hydrogen
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Q
Ionic Bond
A
Electrostatic attraction between (+) and (-) charged ions
Transfer of electron in outer shell to fill void in receptor atom
Produce a moderate strength and moderate hardness bond
4
Q
Covalent Bond
A
electrons are shared between atoms rather than transferred
bond is hard and strong
5
Q
Metallic Bond
A
Electrostatic attractive force in small group of metals
Electrons in higher-energy level shells are shared among several atoms and very loosely held, so they drift from atom to atom
Forms unique properties: opaque, malleable, good conductors
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Q
Van der Waals and Hydrogen Bond
A
weak secondary attraction between specific molecules
very weak bond
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Q
Backbone of minerals
A
complex ions
8
Q
4 main methods of mineral formation
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Chemically, biologically, cooling from melt, metamorphism
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Q
Chemical mineral formation
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low T, Supersaturation from fluid or low temperature alteration
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Q
Biological mineral formation
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low T, Skeleton, external hard parts, internal body, plants, microbes
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Q
Cooling from melt formation
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high T, Crystalline precipitation from magma
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Q
Metamorphism formation
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high T, Solid state change (no melting) due to heat, pressure, hot fluids
13
Q
Are anions or cations larger, and why?
A
Anions are larger because extra electrons pull on electron less, allowing it to move further from the nucleus
Cations are smaller because fewer electrons make the remaining ones pack together tightly, close to nucleus
14
Q
Crystal
A
any solid body that grows with planar surfaces
15
Q
Crystal faces
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planar surfaces that bound a crystal
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Q
Crystal form
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geometric arrangement of crystal faces; interfacial angles are constant
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Q
Growth Habit
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characteristic crystal form of each mineral
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Q
Luster
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the quality and intensity of light reflected from a mineral
19
Q
Main types of luster
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Metallic: polished metal
Vitreous: glass
Resinous: like resin
Pearly: shiny
Greasy: like surface covered by film of oil
20
Q
Color
A
determined by chemical composition, but due to ionic substitution, can be misleading for identifying minerals
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Q
Streak
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color of mineral scratched on an unglazed porcelain plate
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Break Cleavage
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mineral tendency to break in preferred directions along planar surfaces; crystal tends to break along smooth planar surfaces
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Hardness
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a mineral’s relative resistance to scratching
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Q
High density
A
atoms are closely packed together
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Low density
loosely packed atoms
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3 key mineral groups (ALL ANIONS)
Silicate minerals, most abundant in Earth’s crust
Carbonate, Phosphate, and Sulfate
Ore minerals
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What clues do minerals provide?
environment of formation
Mineral type gives indication of temperature and pressure of formation
Minerals and their chemistry give clues to climate and weathering, seawater composition
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3 main types of rocks
igneous, sedimentary, metamorphic
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How does an igneous rock form?
through the cooling and solidification of magma, random interlocking of mineral grains (like a jigsaw puzzle)
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Size equals the
cooling rate
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Extrusive Igneous rock
When magma cools on Earth’s surface, extruded out, fine crystalline rock and small crystals
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Intrusive Igneous rock
When magma cools within existing rocks in Earth’s crust (beneath the surface), you get coarse crystalline rock
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Aphanite
fine crystalline rock and small crystals
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Phanerite
coarse crystalline rock
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What is the mechanism to melt rock and form magma?
increase the heat and reduce the rock melting temperature
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What are the 3 basic sources of magma?
basaltic, andesitic, and rhyolitic (BAR)
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Basaltic magma
deep in the asthenosphere, mostly ocean crust but some continental
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Andesitic magma
mostly subduction zone, ocean-continent type
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Rhyolitic magma
mostly continental affinity
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Basaltic volcanoes
spreading ridges, within plates in oceanic crust (Hawaiian hotspot) or continents
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Andesitic volcanoes
subduction zones, near continents
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Rhyolitic volcanoes
beneath continental plates
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Partial Melting Theory
Mantle peridotite rock partially melts to form basalt magma (dry process)
Basalt rock partially melts to form andesite magma (wet process)
Andesite rock partially melts to form rhyolitic magma (wet)
Thus, B → A → R (basalt to andesite to rhyolite)
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"One Magma Model"
first, everything is melted together, and as it cools, you form different kinds of rocks, and because rocks form at different cooling temperatures, you will form B → A → R
(there are some problems with Bowen's model, which led to the Partial Melting Theory used today)
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Origin of basaltic magma
Comes from partial melting (of peridotites) in the mantle
NO water, so mostly dry process
Less explosive, lava flows
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Origin of andesitic magma
Melting near subduction zone
Wet partial melting of mantle rock
Occurs mostly at the edge of continents near subduction zones
Oceanic plate subducts under continental plate
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Origin of rhyolitic magma
Continental source
Extrude large amounts of water vapor and water-bearing minerals
comes from andesitic (wet process)
Heat source comes from underlying mantle upwelling
High viscosity, rises very slowly, and solidifies as pressure declines; tends to form large intrusive igneous rocks
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Ophiolites
uplifted, exposed fragments of oceanic crust and mantle
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Mafic minerals
rich in silica, magnesium, and iron
Usually dark colored
Oceanic crust
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Felsic minerals
rich in silica, sodium, potassium
Usually light colored
Continents
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What are the big 7 igneous rocks?
granite, rhyolite, basalt, gabbro, diorite, andesite, peridotite
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Plutons
bodies of intrusive igneous rock
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Minor pluton structures
dike, sill, laccolith
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Dike
tabular sheet-like body of igneous rocks that cuts across the rock it intrudes; like a giant wall that runs up and down vertically
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Sill
tabular and sheet-like igneous rocks that run parallel to layering or fabric, typically horizontal
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Laccolith
similar to sill but layers above intrusion are bent upward into a dome shape
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Major pluton structures
stocks, batholiths
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Stock
irregularly shaped and relatively small
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Batholith
cuts across layering and fabric of the host rock
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How do MOST sedimentary rocks form?
from the sedimentation of materials transported in solution or suspension
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How are sediments transported?
water, ice, wind, gravity
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What is the ultimate fate of most sediment?
burial and conversion to sedimentary rock
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3 broad classes of sediments
clastic, biogenic, chemical
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Clastic
loose fragments of rock debris produced mostly by physical weathering (gravel, sand, silt, clay - all different sized grains)
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Biogenic
composed of fossilized remains of plants or animals
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Chemical
precipitates from solution (water)
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4 basic classes of clastic sedimentary rock
Conglomerate (rounded) / Breccia (angular)
Sandstone
Siltstone
Mudstone / Shale
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Poorly-sorted
wide range of particle size (chaotic, haphazard, various sizes)
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Well-sorted
range of grain size is small and uniform
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Till
non-sorted (non-rounded) sediment of glacial origin
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Cross Bedding
comes from turbulent flow; creates inclined beds in thicker stratum
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Graded Bedding
particles are sorted more or less according to size, grading upward from coarser (at the bottom) to finer (at the top)
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Rhythmic laminations
varves; a pair of sedimentary layers deposited over a single year (usually in a lake or restricted ocean basin)
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2 main ways of forming chemical sediments
evaporative concentration in bodies of water
inorganic precipitation in water
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Examples of chemical sedimentary rocks
ooids, evaporites, banded iron formation, phosphate, chert
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What is the most important biogenic rock?
Limestone
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What do vertical changes in strata show?
passage of time and/or conditions
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What do horizontal changes in strata show?
change over distance
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Facies
lateral change from one depositional environment to another
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Non-Marine modern sedimentary depositional facies
1. Stream and river sediments
2. Lake sediments
3. Glacial sediments
4. Eolian (windblown) sediments
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Marine modern sedimentary depositional facies
1. Deltaic sediments
2. Estuarine sediments
3. Nearshore sediments
4. Offshore sediments
5. Carbonate shelves and platforms
6. Marine evaporate basins
7. Deep-sea fans
8. Deep-Sea Oozes
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Diagenesis
how sediment becomes rock
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Lithification
overall process of creating sedimentary rock
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Cementation
substances dissolved in water precipitate out to form a cement that binds grains together
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Recrystallization
less stable minerals recrystallize into more stable forms
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How do metamorphic rocks form?
Heat and pressure → crystallization → metamorphic rock
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What kind of state change is metamorphism?
SOLID, so no liquid is involved
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Different types of metamorphism
contact, low grade, medium grade, high grade
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6 major factors in metamorphism
Chemical composition of precursor rocks
*Change in T
*Change in P
*Presence or absence of fluids
How long a rock is subjected to high P or high T
Whether the rock is simply compressed or deformed under high P
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What is the greatest factor in determining the mineral assemblage of a metamorphic rock?
the composition of the original rock
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Low-grade metamorphism
high T but relatively low P; forms slaty cleavage
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High-grade metamorphism
high T and high P; forms schistosity
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Uniform stress
pressure is equal in all directions
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Differential stress
pressure is different in different directions; produces foliated texture
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Prograde metamorphic effects
wet process; Metamorphic changes that occur while T and P are rising
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Retrograde metamorphic effects
dry process; Metamorphic changes that occur as T and P are declining
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Coarse-grained rocks
products of long, sustained metamorphic conditions (millions of years) and high T and P
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Fine-grained rocks
products of lower T and P, or in some cases, shorter reaction times
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What is the speed of a dry reaction?
very slow because no intergranular fluids present
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When does metamorphism STOP?
when the rock starts to melt
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Metamorphic rocks formed from shale and mudstone
slate (low), phyllite (intermediate), schist and gneiss (high)
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Metamorphic rocks formed from basalt
greenschist → amphibolite → granulite (low → intermediate → high)
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Metamorphic rocks formed from limestone
marble
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Metamorphic rocks formed from sandstone
quartzite
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4 basic settings of metamorphosis
contact, burial, regional, cataclastic
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Contact
Dominated by recrystallization due to proximity of magma (not a lot of P or foliation, but high T)
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Burial
Dominated by recrystallization aided by water and heat
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Regional
Both mechanical deformation and chemical recrystallization
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Cataclastic
Dominated by mechanical deformation that leads to physical deformation
“Cataclysmic pieces” (lots of chunks, lots of pressure, stuff going on, mostly high P and low T)
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Metasomatism
process in which rock compositions are distinctively altered through exchange w/ ions in solution
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Active volcano
eruption since last Ice Age
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Dormant volcano
no eruption since last Ice Age but may erupt
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Extinct volcano
not expected to erupt
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What are volcanoes, essentially?
vents that allow magma to erupt on the surface
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What dominates magma composition?
silica
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What does thicker magma mean?
more viscous and more gas bubbles trapped inside
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Main gases of magma
water vapor and carbon dioxide
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Importance of volcanic gases
Influence atmosphere composition
Rates of outgassing controls the violence of eruption (how fast gases come out of solution)
Gas-driven eruptions put dust in the atmosphere, cooling the global temperature
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What does viscosity depend on?
temperature and composition
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What determines eruptive potential?
gas bubble volume
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Phreatic eruption
caused by groundwater flashing to steam in a hydrothermal explosion, magma + water = near-instantaneous evaporation to steam
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Pumice
a froth of innumerable glass-walled bubbles
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Plinian Eruption
Hot, turbulent mixture rises rapidly in cooler air above vent to form an eruption column
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Pyroclasts
all magma and rocks debris that is ejected into the atmosphere from a volcano; subdivided by size
Bombs (largest)
Lapilli (larger)
Ash (smallest)
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Lateral blasts
magma forces upward, bulges the flank of the volcano, making the flank unstable and it collapses
Creates huge landslide that removes the side of the volcano, decreasing the pressure on magma, allowing the gas to escape in a massive lateral blast
Blows out rock, pyroclasts, gases, both sideways and upwards
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2 broad families of volcanoes
central vent eruptions (mountainous) and long fissure eruptions (come from big crack, not a singular point)
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3 classes of mountainous
shield, tephra, stratovolcanoes
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Shield
Typical of flowing lava (basaltic), low-viscosity lava
Broad, dome-shaped mound
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Tephra
Steep-sided built by successive layers of tephra around central vent
Slope determined by size of pyroclasts
Usually formed in rhyolitic and andesitic volcanoes
Built by pyroclastic debris around a volcanic vent
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Stratovolcano
Combo of lava flows and pyroclasts form large, steep, conical mounds
Form classic snow-capped volcanoes
Contain open crater (caldera) at summit
