Igneous Rock Classification Flashcards
2.5-2.10
Three main igneous textures
crystalline
fragmental
glassy
define aphanitic
fine grained crystals grow quickly under conditions of rapid cooling, typically in extrusive settings
1 stage of cooling
define phaneritic
coarse grained crystals grow larger by cooling slowly typically intrusive
1 stage of cooling
defined porphyritic
both small and large crystals (called phenocrysts)
initial slow cooling followed by rapid cooling (usually after eruption)
2 stages of cooling
texture of rhyolite andesite and basalt
aphanitic
texture of granite diorite and gabbro
phaneritic
mafic melts have a high proportion of
magnesium and iron relative to silica
mafic rocks are usually ___ colored
dark
mafic rocks have ____ specific gravity than felsic
higher
Basalt and diorite M/F
Felsic color
lighter
felsic specific gravity
lower than mafic
rhyolit and granite M/F
felsic
Grain size has to do with
history not composition
peridotite M/F A/P I/S/M
ultramafic phaneritic igneous
andesite M/F A/P I/S/M
intermediate anphanitic igneous
komatite / picrite M/F A/P I/S/M
ultramafic anphanitic igneous
granite M/F A/P I/S/M
felsic phaneritic igneous
freezing temp is proportional to __ density __ silica content ____how mafic it is
+ - +
what is pumice
felsic rock full of vesicles
it floats
glassy igneous rock
what is scoria
vesicular and glassy mafic rock
glassy igneous
what is obsidian
glassy felsic rock, no vesicles
glassy igneous
what the 3 main glassy igneous rocks
pumice
scoria
obsidian
what are the pyroclastic igneous rocks
tuff: fused volcanic ash
volcanic breccia : angular fragments that have fused together
a volcano is
a mountain constructed by the eruption of molten rock from earths interior
volcanoes are a direct consequence of
plate tectonics and mantle convections
Products of volcanic eruptions
lava flows
volcanic gases
pyroclastic debris
lava flows are
molten rock that moves over the ground
volcanic gases are
expelled vapor’s and aerosols
pyroclastic debris are
fragments blown out of a volcano
in violent eruptions
gas escape is difficult
in mellow eruptions
gas escape is easy
mellow eruptions have _ viscosity
low
violent eruptions have _ viscotisy
high
basaltic lava has
low viscosity and can travel long distances
andesitic lava is
too viscous to flow far and tends to break up as it flows
felsic lava is
so viscous that it may pile up in a dome shaped mass
basaltic lava flows are
very hot, mafic, low viscosity
basalt flows are often
thin and fluid
go long distances
Lava tubes are
conduits for basaltic lava
andesitic lava flows have
higher silica , a bit viscous, mound the vent and slow f lowly, cooled crust cracks into rubble
rhyolitic lava flows
high silica (felsic), more viscous, don’t really flow at all, can be blown out during an eruption
rhyolitic eruptions look like
big smoke clouds
pyroclastic flows are
flow of hot molten pyroclastic debris,
500-1000C ash that travels at up to 300 Km/h
Tuff is
lithified ash
an air fall tuff accumulates like
snow
an ignimbrite is a
tuff that is deposited while still hot; it welds together
pyroclastic debris can trap
volcanic gas
pyroclastic debris has ____ specific gravity
low
3 types of volcanoes
shield volcanoes
cinder cones
stratovolcanoes
magma chambers are located
in the upper crust
fissures happen when
magma erupts along a linear tear
or through a pipe shaped conduit with a crater at the top
a crater is
a bowl shaped depression atop a volcano
a caldera is
a gigantic volcanic depression, they quickly fill with water and become a lake
calderas are _____ than craters
much larger
shield volcanoes are shaped like
a dome
shield volcanoes have what kind of lava
low viscosity basaltic
shield volcanoes have ___ violent eruptions
not very
what kind of volcano is hawaii
shield volcano
cinder cones are what shape
a cone dumbfuck no shit
cinder cones are the smallest type of
volcano
cinder cones form from
ejected fragments that have built up at the angle of repose around the vent
stratovolcanoes are also known as
composite volcanoes
stravolcano shape
large cone shape, steep slopes
stratovolcanoes are made of
alternating layers of felsic lava tephra and debris
mt st helen’s, mt fuji, mt vesuvius and mt pinotubo are all what kind of volcano
stratovolcano
stratovolcanoes have a ____ violent eruption
VERY
rank the following in size, caldera,
cinder volcanoes, shield volcanoes, stratovolcano small to large
cinder
strato
caldera
shield
3 main Eruption styles
effusive
explosive
plinian
effusive characteristics
outpouring of basaltic lava
rivers of lava
lava lakes can form near the vent
lava fountains 500 m high
explosive characteristics
high gas pressure
more viscous siO2 rich
mostly andesitic and rhyolitic
Plinian characteristics
often destroy a part of the stratovolcano that created them
create a convective cloud
why are they called plinean
roman scholar pliny saw vesuvius erupt
what is a lahar
volcanic ash and debris mixed with water which travel along drainage ways
when do lahars occur
snow ice or rain
eruption or not
volcanoes cause landslides as
movement destabilizes flanks
debris falls off the mountain
volcanoes cause tsunamis by
destabilizing flanks or caldera collapse
active volcanoes
are erupting, have erupted recently, are likely to erupt
dormant volcanoes
haven’t erupted in hundreds to thousands of years
extinct volcanoes
are no longer capable of erupting
to predict eruptions
magma movement causes a change in shape that can be measured with tiltmeters or satellite radar
to mitigate volcanic hazards
don’t build near them
don’t build on lahar drainage routes
pinatubo is what eruption type
plinian
mount kilauea is what type of volcano
shield volcano
mount kilauea has what eruption type
hawaiian (i know its stupid)
Eyjafjallajokull has what type of eruption
strombolian (i know what the fuck)
white island eruption type
phreatic
vesuvius eruption type
plinian or vesuvian
nyiragongo volcano type
stratovolcano
hawaiian characteristics
predominately effusive, flows with minor scoria
strombolian characteristics
periodically erupts a fountain of scoria lapilli and ash
vulcanian characteristics
erupts both scoria tapili and tall plumes of pyroclastic debris
phreatic characteristics
groundwater interacts with magma producing a steam explosion and blocks of wall rock
phreatomagmatic characteristics
eruption involves steam explosion but also eruption of wet ash, lapilli, and blocks of lava
surtseyan characteristics
seawater enters the magma chamber and does phreatomagmatic making steam explosions
nyiraragongo is on lake
kivu
nyirgongo is characterized by its
vents and fissures
limnic eruptions are
eruptions of gases in a lake, slow release of poison
lake nyos eruption type
limnic
