Crater Lake

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Crater Lake Jena Hershkowitz and Ethan
Farina-Henry
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
Magmas tend to rise. Less dense than solid
rock. Liquid rock has more volume than
solid. Rise is controlled by FLUIDITY of the
magma. FLUIDITY is a fluids ability to
flow. Governed by temperature and
composition. Greater heat greater fluidity of
magma. Lower silica content greater fluidity of
magma.
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
Movement of magma also related to
VISCOSITY. VISCOSITY is fluids resistance to
flow. Opposite of fluidity. Greater viscosity of
magma, the lower the ability to flow. Cool
magmas flow sluggishly, while hot magmas
flow easily. Viscosity also increases with
silica content.
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
Magma composition reflects silica content. Felsic
magmas have higher silica content so felsic
magmas have greater viscosity. Felsic magmas also
form at lower temperatures so felsic magmas
again are less likely to flow. Felsic magmas and
lavas consequently are much more explosive than
mafic magmas and lavas.
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
Mafic magmas have low silica content so
mafic magmas have lower viscosity. Mafic magmas
also from at higher temperatures so mafic magmas
will flow easily. Mafic magmas have greater
ability to rise to the surface. Mafic magmas
and lavas generally produce very quiet eruptions.
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
All magmas eventually cool and crystallize. Melti
ng temperature and freezing temperature is the
same for each individual mineral. Just the
direction of the reaction changes. Minerals that
melt first when a rock is heated, also tend to
crystallize last when a magma is
cooled. Partially cooled magma will contain
solid mineral crystals that crystallize at high
temperature. It will also contain ions that may
crystallize later.
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
Bowens Reaction Series
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
OTHER POSSIBILITIES
FRACTIONAL CRYSTALLIZATION
Earlier forming crystals are denser than
magma. Sink to the bottom of magma
chamber. Changes composition of magma.
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
Palisades Sill, NJ
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IGNEOUS PROCESSES AND IGNEOUS ROCKS
Bushveld Complex, S. Africa