Rocks at 560* C do not support magnetism

Averages around 10-20km in depth

Yellowstone: 4-6km in depth

Surficial uprising in a ring formation has been noticed by seismic imaging of subsurface at Yellowstone

1996-2000

Age of islands become progressively older toward the NW

Shield Volcanoes

Overlapping volcanic centers

Actual Height: 33,500 feet tall

Above Water: 13,800 feet tall

*Taller than Mt. Rainier

Low-viscosity eruptions, runnier

1984: Magma flowed 16 miles in 5 days

1) Fissure eruptions

2) Fire fountains

3) Lava lakes

4) Lava rivers/flows

Made up of Scoria (pyroclasts)

Secondary features on volcanoes, near the vents

Surface of a lava river crusts over, while hot lava continues to flow beneath

Lava drains, leaving behind the crusted-over walls and ceilings

Localized collapse of the lava tube

Good for sampling

The place where lava meets the Pacific Ocean

Ground is extremely unstable here, can slump off into the water at any moment

Keonehelelei

1790

Explosive eruption

"The falling sand"

Civil war of the Big Island -- The defeat of Keoua's army and the rise of the Great King Kamehameha

Greece

Plates are spreading and rotating

Many little clusters of volcanoes that tend to be very explosive

Grond Layers (Surface --> Down)

Phase 3: Ash flow deposits

Phase 2: Surge deposits

Phase 1: Air-fall deposits

Precursor ash layer

Older volcanic deposits

1650 BCE

Santorini

Probable cause of the end of the Minoan civilization on Crete

Explosive

Surges have low particle density

Flows have high particle density

Relative Time:

 Older vs Younger

Arrangement into a sequence

Mostly based on sedimentary rock

Absolute Time:

Quantatative

Specification of duration

Mostly based on igneous rocks

Stratigraphy

Faunal Succession

Stratigraphy: Study of layers of material

1) Orginal Horizontality: deposited as horizontal layers (many rocks, esp sedimentary)

2) Superposition: younger material is deposited on top of older material

3) Cross-cutting relations: features (faults, dikes) which cut layers are younger than those layers

4) Inclusion: objects (clasts, fossils) in a sedimentary layer are older than the layer itself

5) Unconformities: lengthy "gaps" in the rock record may be identified by the arrangements of layers

1) Correlation with Egyptian dates (astronomical)

2) Dendrochronology (tree ring date)

3) Varves (lake sediment)

4) Glacial ice core dating (Greenland)

5) Carbon-14 radiometric dating

Tree ring dating

Record of annual growth-rings

Good for overlapping, giving a continuous record

Wide rings: Favorable weather, good year, growth promotion

Thin rings: "opposite"

Limiting conditions/affects ring width: Lack of rain/sun, too cold

Lakes which freeze over have alternating layers of thick, light color sediment (summer) and thin, dark color sediment (winter)

Dark layer: rich in organic material (buried before rotting/consumption) 

Concentration of sulfuric acid in an ice core

Spike in concentration at 1645 BCE (Santorini eruption -- Mediteranean)

Some isotopes are unstable and will fall apart

Unstable atoms (parents) will decay into (daughter) atoms

The ratio of "parent" atoms to "daughter" atoms will indicate how much time has passed since SRD

Falling apart is random, unpredictable, and spontaneous

Isotopes must be present in large quantities

No gain/loss of material at this time (solidification of magma)

*Only good for igneous rocks that are really old

Potassium-Argon dating --> daughter is inert gas, since daughter atoms will easily escape until solidification occurs

"Clock" starts when magma becomes a rock

If the object being measured was once alive

Ex: Animals, humans, plant remains

Dating young volcanic ash layers

Ex: Mazama -- Crater Lake

Volcanic material that effects climate:

Gas

Ash and rock particles

Processes that effect climate:

Ozone Effect

Greenhouse Effect

Haze (Radiation reflection) effect

H2O

CO2

SO2

Toxic gasses:

HCl, HF

H2SO4

H2S

O3 absorbs ultraviolet radiation and heat

Chlorine destroys O3

Volcanic HCl remains mostly in the troposphere

82% of Cl in stratosphere is from CFC

33% O3 reducction due to Pinatubo eruption

Greenhouse gasses trap radiation at surface --> increases temperature

H20, CO2

Armero -- Nevado del Ruiz

Stats

Highest active volcano in South America

Covered with tons of glacial ice

Stratovolcano

Became active with fumaroles in Nov 1984

Erupted in Nov 1985

Eruption at summit generated pyroclastic flows and debris avalanches

Continued blasts, rain and snow, and pyroclastic material landed on summit and flanks

Many lahars were active in all six river valleys

Headwaters of Guali River (lahar travelling 60km/hr; stripping the banks clean)

City of "Rio Lagunillas" lost 75% of the inhabitants

23,000 people killed by lahars within 4 hours after eruption

No warning system set in place

Volcanoes kill 680 people per year

(1600-1986)

Starvation/disease were leading causes of death until 1990, then it was pyroclastic flows and debris avalanches

Risk = (value)x(vulnerability)x(hazard)

Value: Threatened lives, property loss (individual and community)

Phillipines

Very explosive

Unexpected: Intermediate (andesite) magma, not explosive, formed dome

March 1991: Small quakes, fissures

April 1991: Phreatic (steam-blast) eruption. Old hydrothermally altered rock thrown out.

June 1991: Increase in harmonic tremors, low-frequency quakes, series of small eruptions

Mid-June: BIG eruption, top of mountain gone, large caldera formed, material ejected into atmosphere

1-3 months prior: Fresh basalt mixed with old dacit

4 days prior: Hybrid mixture (andesite) intruded through sluggish, crystal-rich dacite --> mobilized dacite

Excess gas was gathering and not being released effectively.

Pressure build up.

Gas wasn't dissolving, so it turned into excess bubbles.

Lahars

upper vs lower

Really thick and muddy at top of slope, but gather speed and accumulate water as it travels down-slope

Getting more dangerous as it goes

Dam that was built in a river channel near Pinatubo.

After eruption, dam sits 30m above the river bed because the river channel sunk so far down after the eruption

Gaseous: Jupiter, Saturn, Neptune, Uranus

Rocky: Mars, Earth, Moon, Venus, Mercury

Impact between Earth and a Mars-sized body

The moon is mostly made of material that was once part of Earth's mantle

Moon is "geologically dead" -- no atmosphere

1) Light, cratered highlands, Anorthocite, old

2) Dark, blotchy mare basins of low-viscosity basalt flows, three distinct phases of volcanic activity

No obvious volcanoes, but some rare volcanic domes

Lunar volcanism is extinct

Only basalt composition

No linear patterns of volcanic mountain chains

No lunar plate tectonics

Lunar gravity is 1/6 that of Earth's

Close in size/density to Earth

Very close to sun, water can't form oceans

Surface temperatures -- hundreds of degrees Celsius

Covered in CO2 cclouds

Very volcanic (mostly shield volcanoes)

Long lava flows & channels due to hot surface temperature