Transcript Volcanoes and Volcanism (Con`t.)

Crater Lake
Jena Hershkowitz and Ethan Farina-Henry
IGNEOUS PROCESSES AND IGNEOUS ROCKS
FLUIDITY AND VISCOSITY OF MAGMA
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 fluid’s ability to flow.
Governed by temperature and composition.
Greater heat greater fluidity of magma.
Lower silica content greater fluidity of magma.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
FLUIDITY AND VISCOSITY OF MAGMA
Movement of magma also related to VISCOSITY.
VISCOSITY is fluid’s 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.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
FLUIDITY AND VISCOSITY OF MAGMA
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.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
FLUIDITY AND VISCOSITY OF MAGMA
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.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CRYSTALLIZATION OF MAGMA
All magmas eventually cool and crystallize.
Melting 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.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
Bowen’s Reaction Series
CRYSTALLIZATION OF MAGMA
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CRYSTALLIZATION OF MAGMA
OTHER POSSIBILITIES
FRACTIONAL CRYSTALLIZATION
Earlier forming crystals are denser than magma.
Sink to the bottom of magma chamber.
Changes composition of magma.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CRYSTALLIZATION OF MAGMA
Palisades Sill, NJ
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CRYSTALLIZATION OF MAGMA
Bushveld Complex, S. Africa