Post on 31-Dec-2015
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Giant’s CausewayLea Korsmeyer
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CRYSTALLIZATION OF MAGMA
ASSIMILATION
MAGMA MIXING
Produces felsic magmas by melting of surroundingcountry rock.Adds silica to magma.
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 liquidadditional 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
Henry Mtns = laccolith
Mushroom-shapedintrusion.
Intrudes layers and pushesoverlying layersupward into a domeshape.
Form at shallow depths.Usually composed of felsic
magmas.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
INTRUSIVE ROCK FORMATIONS
LOPOLITH Saucer-shaped pluton.Generally mafic magma.Weight of magma forces
surrounding layersdownward into thespace evacuated bymagma.
Exhibit fractionalcrystallization.
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 areeroded 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, butarea 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 ridgesIntraplate hot spots or mantle plumesRifting continents
Andesites and Diorites found at subduction zones.Particularly ocean-continent subduction
Rhyolites and Granites also found at subductionzones.Requires partial melting of continental crust.Also found where continents rift.
VOLCANO - landforms generated when magma isreleased from the Earth’s interior through openings.Openings are called VENTS.
Heimaey, Iceland, 1973Surtsey, Iceland, 1963
VOLCANOES AND VOLCANISM
EXTRUSIVE FEATURES
Puu Kamoamoa, HI
VOLCANOES AND VOLCANISM
Nyiragongo,Democratic Republic of Congo
(formerly Zaire)
VOLCANOES AND VOLCANISM
Soufriere Hills,Montserrat
“I don’t know where I’m a gonnago when the volcano blows.”
- Jimmy Buffett
VOLCANOES AND VOLCANISMMt. St. Helens, WA
17 May 1980
VOLCANOES AND VOLCANISM
Mt. St. Helens, WA18 May 1980
VOLCANOES AND VOLCANISMMt. St. Helens, WA
19 May 1982
VOLCANOES AND VOLCANISM
VOLCANISMHas 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.