MGRADES
GEMS Test #3 UPDATED ACTUAL Exam
Questions and CORRECT Answers
mafic (basic) minerals - CORRECT ANSWER - low SiO2 content, <50% by weight, rich
in MgFe, dark rocks, ex: olivine, hornblende, augite
felsic (acidic) minerals - CORRECT ANSWER - contain feldspar and quartz minerals,
>70% by weight, light rocks, ex: orthoplase, clagioplase
intermediate minerals - CORRECT ANSWER - contains biotite or hornblende minerals,
55-67% by weight, grey colored, ex: feldspar, quartz, muscovite
intrusive (plutonic) - CORRECT ANSWER - rocks that were crystallized or cooled slowly
below the surface -- large crystals, easily distinguished PHANERITIC TEXTURE
extrusive (volcanic) - CORRECT ANSWER - rocks that were crystallized/cooled rapidly
on the surface of the earth -- small crystals that aren't easily distinguishable, APHANETIC
TEXURE
porphyritic - CORRECT ANSWER - a texture containing a mix of large and small crystals
typically found in extrusive rocks
gabbro, diorite, granite - CORRECT ANSWER - Mafic intrusive, intermediate intrusive,
felsic intrusive -- chemically similar but textually different
basalt, andisite, rhyolite - CORRECT ANSWER - mafic extrusive, intermediate extrusive,
felsic extrusive -- chemically similar but different textures
high SiO2 content - CORRECT ANSWER - makes magma more viscous (thicker)
, MGRADES
volatiles in magma - CORRECT ANSWER - chemicals in magma in gas form include
H2O, CO2 and H2S
higher viscosity - CORRECT ANSWER - causes eruptions to be more explosive
pillow lavas - CORRECT ANSWER - contain a chill margarine meaning they cool slower
on the inside -- they indicate there was water at the time of the eruption
composite/stratovolcanoes - CORRECT ANSWER - large steep sided volcanos, explosive,
contain high silica content
pyroclastic flows - CORRECT ANSWER - rapidly moving clouds of ash mixed with hot,
suffocating gases
nuee ardente - CORRECT ANSWER - Blast of gas associated with high viscosity
landslides - CORRECT ANSWER - This happened at mount st Helen -- a massive
earthquake cause the top of the mountain to slide off which then caused it to erupt
lahaars - CORRECT ANSWER - Volcanic mud flow
ash - CORRECT ANSWER - Small rock particles that are shot into the atmosphere and
rain down
general global ramifications - CORRECT ANSWER - Ash blocks out the sun and can
change the climate
plateau basalts - CORRECT ANSWER - An extensive, thick, smooth flow or succession
of flows of high-temperature, fluid basalt erupted from fissures ex: eastern washington
topography, keweenaw peninsula
GEMS Test #3 UPDATED ACTUAL Exam
Questions and CORRECT Answers
mafic (basic) minerals - CORRECT ANSWER - low SiO2 content, <50% by weight, rich
in MgFe, dark rocks, ex: olivine, hornblende, augite
felsic (acidic) minerals - CORRECT ANSWER - contain feldspar and quartz minerals,
>70% by weight, light rocks, ex: orthoplase, clagioplase
intermediate minerals - CORRECT ANSWER - contains biotite or hornblende minerals,
55-67% by weight, grey colored, ex: feldspar, quartz, muscovite
intrusive (plutonic) - CORRECT ANSWER - rocks that were crystallized or cooled slowly
below the surface -- large crystals, easily distinguished PHANERITIC TEXTURE
extrusive (volcanic) - CORRECT ANSWER - rocks that were crystallized/cooled rapidly
on the surface of the earth -- small crystals that aren't easily distinguishable, APHANETIC
TEXURE
porphyritic - CORRECT ANSWER - a texture containing a mix of large and small crystals
typically found in extrusive rocks
gabbro, diorite, granite - CORRECT ANSWER - Mafic intrusive, intermediate intrusive,
felsic intrusive -- chemically similar but textually different
basalt, andisite, rhyolite - CORRECT ANSWER - mafic extrusive, intermediate extrusive,
felsic extrusive -- chemically similar but different textures
high SiO2 content - CORRECT ANSWER - makes magma more viscous (thicker)
, MGRADES
volatiles in magma - CORRECT ANSWER - chemicals in magma in gas form include
H2O, CO2 and H2S
higher viscosity - CORRECT ANSWER - causes eruptions to be more explosive
pillow lavas - CORRECT ANSWER - contain a chill margarine meaning they cool slower
on the inside -- they indicate there was water at the time of the eruption
composite/stratovolcanoes - CORRECT ANSWER - large steep sided volcanos, explosive,
contain high silica content
pyroclastic flows - CORRECT ANSWER - rapidly moving clouds of ash mixed with hot,
suffocating gases
nuee ardente - CORRECT ANSWER - Blast of gas associated with high viscosity
landslides - CORRECT ANSWER - This happened at mount st Helen -- a massive
earthquake cause the top of the mountain to slide off which then caused it to erupt
lahaars - CORRECT ANSWER - Volcanic mud flow
ash - CORRECT ANSWER - Small rock particles that are shot into the atmosphere and
rain down
general global ramifications - CORRECT ANSWER - Ash blocks out the sun and can
change the climate
plateau basalts - CORRECT ANSWER - An extensive, thick, smooth flow or succession
of flows of high-temperature, fluid basalt erupted from fissures ex: eastern washington
topography, keweenaw peninsula
