3 MAIN ROCK TYPES: IGNEOUS, SEDIMENTARY, &

METAMORPHIC

IGNEOUS- COOLS FROM MOLTEN ROCK

SEDIMENTARY- RECOMBINED FRAGMENTS OF MINERALS, ROCKS, &/OR ORGANIC ORIGIN

METAMORPHIC- PRE-EXISTING ROCKS CHANGED IN COMPOSITION, MINERALOGY, OR TEXTURE FROM HIGH TEMPERATURES, PRESSURES, &/OR FLUIDS

THE ROCK CYCLE - CONSTANT REWORKING OF ROCKS IN THE EARTH'S INTERIOR & AT SURFACE BY DEFORMATION, WEATHERING, EROSION, ETC... TO FORM NEW ROCKS

Phase (Pressure-Temperature) Diagram for

Lithospheric & Asthenospheric Depths

Most regions of the outer 200 km of the earth DO NOT have melt!

TEMPERATURE VS DEPTH (GEOTHERM)Davidson 4.2

IGNEOUS ROCKS

SILICATE MATERIAL (WITH GASSES) MELTS AT DEPTH

MELTED MAGMA LESS DENSE THAN SURROUNDING SOLID SO RISES

INTRUSIVE ROCK: SOLIDIFIES ("CRYSTALLIZES”/"FREEZES") AT DEPTH

EXTRUSIVE ROCK: LAVA ERUPTS AT SURFACE & FORMS.

COOLING LAVA RELEASES GASSES INTO ATMOSPHERE

IGNEOUS ROCKS CLASSIFIED BY THEIR CHEMICAL COMPOSITION (HOW MUCH SiO2 ), MINERALS, AND INTRUSIVE OR EXTRUSIVE

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.“every rock and tree and creature has a life, has a spirit, has a name…”

IGNEOUS ROCKS classified by chemical composition & cooling rate

Felsic- more FELdspar and SIlica

Mafic- more Magnesium and iron (Fe) ----------------------Texture reflects cooling:

Extrusive/Fine Grain

Intrusive/Coarse Grain

LESS DENSE MORE DENSE

LESS SiO2

SiO2

(Mg,Fe)2SiO4

Davidson 4.4

THREE IMPORTANT PAIRS OF IGNEOUS ROCKS

RHYOLITE / GRANITE (>63% SiO2): MOST OF CONTINENTAL CRUST, DENSITY ABOUT 2.8 g/cm3 , FORMS BY MELTING CONTINENTAL CRUST

ANDESITE */ DIORITE (63-52% SiO2) FROM MELTING OCEANIC CRUST, OFTEN AT SUBDUCTION ZONES

BASALT / GABBRO (<52% SiO2) MOST OF OCEANIC CRUST, DENSITY ABOUT 3.3 g/cm3, FROM MELTING MANTLE, OFTEN AT MIDOCEAN RIDGES

BECAUSE GRANITE IS LESS DENSE THAN BASALT:

CONTINENTS "FLOAT" HIGHER THAN THE OCEAN CRUST SO WE LIVE ABOVE SEA LEVEL

CONTINENTS NEVER SUBDUCT BACK INTO THE MANTLE SO FORMED EARLY IN EARTH HISTORY & ARE OLD (LESS THAN 500 MYR TO 4 BYR), COMPARED TO OCEANIC CRUST THAT SUBDUCTS SO IS YOUNG (0-200 MYR)

*LIKE ANDES

Igneous rock textures formed primarily by cooling rate

LARGE GRAINS SMALL GRAINS LARGE & SMALL GRAINS

MICROSCOPE IMAGE

Davidson 4.4

SINGLE CRYSTAL GROWING FOR INTEGRATED CIRCUIT (IC or MICROCHIP) PRODUCTION                            

ICs are built on single-crystal silicon substrates of high purity and perfection. Single-crystal silicon is used instead of polycrystalline silicon since the former does not have defects associated with grain boundaries.

- Silicon inside the chamber is melted (Si melts at 1421 deg C).

-  A slim seed of crystal silicon (5 mm dia. and 100-300 mm long) is introduced into the molten silicon.

-  The seed crystal is withdrawn at a very controlled rate, and grows.

- Wafers are sliced off the crystal  and circuits built on them

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AS MAGMA COOLS MINERALS FORMDEPEND ON TEMPERATURE ("FRACTIONAL CRYSTALIZATION")

REVERSE PROCESS OCCURS DURING MELTING ("PARTIAL MELTING")

PROCESS ILLUSTRATED WITH HALF-FROZEN APPLE JUICE

FRACTIONAL CRYSTALIZATION /PARTIAL MELTINGAS MAGMA COOLS SOLID MINERALS THAT "FREEZE" OUT DIFFER IN COMPOSITION FROM REMAINING LIQUID

CRYSTALLIZATION OF MAGMA AS TEMPERATURE DROPS

Davidson 4.6

CRYSTALS SINK TO BOTTOM

SiO2-POOR MINERALS FREEZE OUT

MAGMA BECOMES MORE SiO2-RICH

Evanston’s population “ages” over summer break

http://science.howstuffworks.com/oil-refining2.htm

Higher temperature, lower viscosity (warm syrup flows more easily than cold)

Viscosity increases with increasing silica content due to silica chains

High viscosity lavas flow slowly and typically cover small areas. Low viscosity magmas flow more rapidly and cover thousands of square km.

Low viscosity magmas allow gases to escape easily.

Gas pressures can build up in high viscosity magmas - so violent eruptions (Blowing through a straw, it's easier to get water to bubble than a milk shake)

MAGMA VISCOSITY- VOLCANIC ERUPTION CHARACTERISTICS LARGELY CONTROLLED BY THE VISCOSITY - "GOOEYNESS" (RESISTANCE TO FLOW) - OF THE MAGMA: LOW VISCOSITY FLUIDS FLOW MORE EASILY THAN HIGH VISCOSITY FLUIDS

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High viscosity magma- SiO2 rich

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Low viscosity magma- low SiO2

MAGMA VISCOSITY & VOLCANO TYPE

High viscosity lava flow slowly & typically cover small areas, forming composite volcanoes (stratovolcanoes) (e.g. Mt. St. Helens) that explode violently due to trapped gas

Low viscosity lavas flow rapidly & form shield volcanoes (e.g. Hawaii) with flows covering thousands of square kilometers

Mount Saint Helens- stratovolcano (composite volcano) with viscous dacitic (SiO2-rich) magma containing lots of dissolved gas (mostly water vapor), before 1980 explosive eruption, after, & today

BEFORE

AFTER

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JANUARY 2005- NEW ASH & DOME FORMING IN CALDERA

Successive stages of development of Crater Lake, Oregon

Davidson 4.15

2002 ERUPTION: BIG ISLAND OF HAWAII

Brian White (CAS 2000)Seth Stein

http://hvo.wr.usgs.gov/cam/index.htm

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Different types of volcanoes at different tectonic settings

Davidson 4.16

Japan,Aleutians

East African Rift

St Helens,Andes

The two main ways in which melting occurs in the mantle

MELTING AT LOWER PRESSUREWATER LOWERS MELTING

TEMPERATURE

MIDOCEAN RIDGE SUBDUCTION ZONE

GEOTHERM - TEMPERATURE vs DEPTH

SOLIDUS - MELTING CURVE

ACTIVE VOLCANOES CONCENTRATED AT PLATE BOUNDARIES

Stands 27 kilometres (88,600 feet) high over its base (about three times the height of Everest above sea level)

Caldera is 85 km (53 miles) long, 60 km (37 miles) wide, and up to 3 km (1.8 miles) deep with six overlapping pit craters.

Outer edge is defined by an escarpment up to 6 km (4 miles) tall unique among the shield volcanoes of Mars.

Olympus Mons is roughly the size of the state of Missouri

MARS: Olympus Mons

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What type of volcano is Mt. Doom (Orodruin) in the “Lord of the Rings”?