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Giant’s Causeway
Lea Korsmeyer
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CRYSTALLIZATION OF MAGMA
ASSIMILATION
Produces felsic magmas by melting of surrounding
country rock.
Adds silica to magma.
MAGMA MIXING
Two different magma chambers merge and magmas
mix producing magma of new composition.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
Magma generally moves forcefully into cracks in
pre-existing rocks.
Because volume expands when rock becomes liquid
additional fracturing occurs.
Magma moves into these newly created spaces.
PLUTON - any subsurface intrusive igneous body.
COUNTRY ROCK - pre-existing rock surrounding
intrusive igneous body.
XENOLITH - piece of pre-existing rock in intrusion.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
COUNTRY ROCK
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
XENOLITH
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
DIAPIR
A dome shaped igneous intrusion within other rocks.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
TABULAR PLUTONS - slab-like intrusions
DIKE - a discordant tabular pluton
Pluton cuts across the pre-existing bedding.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
Shiprock, NM
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
TABULAR PLUTONS - slab-like intrusions
SILL - a concordant tabular pluton
Pluton intruded parallel to pre-existing bedding.
Antarctica
Salt River Canyon, AZ
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
LARGE PLUTONS
Typically > 3 or 4 kilometers thick.
Up to 100’s of kilometers in length.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
LACCOLITH
Mushroom-shaped
intrusion.
Intrudes layers and pushes
overlying layers
upward into a dome
shape.
Form at shallow depths.
Usually composed of felsic
magmas.
Henry Mtns = laccolith
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
LOPOLITH
Saucer-shaped pluton.
Generally mafic magma.
Weight of magma forces
surrounding layers
downward into the
space evacuated by
magma.
Exhibit fractional
crystallization.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
BATHOLITH
Half Dome, Yosemite, CA
Massive discordant intrusion.
Exposed surface >100 km2.
Composed of diorites and
granites.
Can occur as multiple events
e.g. Sierra Nevada.
Form at depths up to 30 km.
Generally form elongate
mountain ranges.
Also found in central parts of
continents but are
eroded flat.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
BATHOLITH
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
STOCK
Large igneous intrusion, similar to batholith, but
area is less than 100 km2.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
IGNEOUS ROCKS AND PLATE TECTONICS
Most igneous rocks are associated with plate boundaries.
Gabbros and basalts at:
Mid-oceanic ridges
Intraplate hot spots or mantle plumes
Rifting continents
Andesites and Diorites found at subduction zones.
Particularly ocean-continent subduction
Rhyolites and Granites also found at subduction
zones.
Requires partial melting of continental crust.
Also found where continents rift.
VOLCANOES AND VOLCANISM
EXTRUSIVE FEATURES
VOLCANO - landforms generated when magma is
released from the Earth’s interior through
openings.
Openings are called VENTS.
Surtsey, Iceland, 1963
Heimaey, Iceland, 1973
VOLCANOES AND VOLCANISM
Puu Kamoamoa, HI
Nyiragongo,
Democratic Republic of Congo
(formerly Zaire)
VOLCANOES AND VOLCANISM
“I don’t know where I’m a gonna
go when the volcano blows.”
- Jimmy Buffett
Soufriere Hills,
Montserrat
VOLCANOES AND VOLCANISM
Mt. St. Helens, WA
17 May 1980
VOLCANOES AND VOLCANISM
Mt. St. Helens, WA
18 May 1980
VOLCANOES AND VOLCANISM
Mt. St. Helens, WA
19 May 1982
VOLCANOES AND VOLCANISM
VOLCANISM
Has produced most of the water
on Earth.
Has vastly modified the Earth’s
atmosphere.
Has created new land.
Produces fertile agricultural land.
Provides a source of geothermal
energy in Italy, Iceland and
California.
Presents significant natural hazard.