Topic 4B Flashcards
extrusive
fast cooling (small minerals)
intrusive
long cooling (large minerals)
glassy characteristics
glassy, cools quickly, extrusive
aphanitic
small crystals, cools quickly at lower temp, extrusive
phaneritic
large crystals, cools slowly at high temp, intrusive
porphyrite
two crystal sizes, intrusive
pyroclastic
fragments of crystals
vesicular
holes, pores
Felsic Minerals in general
light in color
light in weight (Fe,Mg poor)
Found in intermediate and felsic rocks
mafic minerals in general
dark in color
heavier(Fe,Mg rich)
found in mafic and ultramafic rocks
Felsic Rocks
Rhyolite (extrusive)
Granite (Intrusive)
Intermediate rocks
Andesite ( extrusive)
Diorite (intrusive)
Mafic rocks
basalt (extrusive)
gabbro (intrusive)
Ultramafic rocks
Rare (extrusive)
Peridotite (intrusive)
intermediate magma can form through
crystal settling in a mafic magma
partial melting of mafic rock
mixing mafic magma with felsic magma
assimilating felsic rocks into mafic magma
felsic magma can be formed through
crystal settling in an intermediate magma
partial melting
What is a volcano
any landform (earth or ocean) that releases lava, gas or ashes or has done so in the past
Mostly occur at divergent or convergent boundaries
Mafic Magma characteristics
thin and flows easily
low silica content
low viscosity
low gas
forms Aa and
Pahoehoe lavas
Felsic Magma characteristics
thick
tends to erupt catastrophically
high silica content
more viscous
high gas
Pyroclastic debris in ascending mass
ash,lapilli, volcanic bombs, volcanic block, welded tuff, pumice
what are the 3 most abundant gases released in an eruption
H20
CO2
SO2
central vent volcanoes characteristics
central vent
summit crater
has 4 types
shield volcanoes
cinder cones
stratavolcanoes
rhyolite caldera complexes
Large scale volcanic terrains
no central vent
network of source material
extend over large areas
Shield volcanoes characteristics
low viscosity creates broad, gentle slops
low silica, low gas, magma comes from mantle
Stratovolcanoes characteristics
Alternating layers of mafic to intermediate lava flows with layers of intermediate to felsic explosively pyroclastic fragments (explosions due to gas buildup)
Rhyolite caldera complexes characteristics
High silica, high gas magmas
massive explosions ( most explosive)
withdrawal of magma from magma chamber causes collapse
Large scale volcanic terrains characteristics
mid-ocean ridges develop divergent boundaries (spreading centres)
basaltic flow creates a global network
tectonic environment- divergent boundary
mafic lava flows (efussive)
mid ocean ridge
tectonic environment- oceanic hot spot
mafic lava flows
shield volcanoes
tectonic environment- continental hot spot
felsic to mafic lava flows
shield volcanoes (rare)
stratavolcanoes (common)
rhyolite caldera complexes
tectonic environment- oceanic/continental subduction zones
felsic to mafic lava flows
volcanoes form volcanic arc
stratavolcanoes or rhyolite caldera complexes
tectonic environment- oceanic/oceanic subduction zones
Intermediate to mafic lava flows
volcanoes form and island arc
shield volcanoes or stratavolcanoes
