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 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. BATHOLITH Half Dome, Yosemite, CA

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

Democratic Republic of Congo 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 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.