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.