Today – 4/13Today – 4/13 More volcanoes!More volcanoes!

First Mars shot - hillFirst Mars shot - hill

Matian basaltMatian basalt

Martian dune fieldMartian dune field

Frozen Martian SeaFrozen Martian Sea

Last Time

Hotspots – mantle plumes reach the surface; decompression melting to form basaltic magma; Hawaii, Mars, Venus; independent of plate boundaries

Intrusive v. extrusive: coarse v. fine texture depends on cooling rate

Three kinds of volcano: shield, stratovolcano, caldera – depends on magma type

Last Time – Shield Volcano

Built up from repeated basalt flows

Basalt has high Fe / Mg, high temperature, low Si, low gas content, low viscosity (stickiness)

MOR’s, hotspots, areas of continental extension

StratovolcanoStratovolcano Built from alternating Built from alternating

layers of pyroclastic & layers of pyroclastic & andesite lava flows andesite lava flows

Magma – intermediate Magma – intermediate temperature, gas temperature, gas content, composition, content, composition, viscosityviscosity

St. Helens, Monserrat, St. Helens, Monserrat, Pinatubo, TamboraPinatubo, Tambora

Form above subduction Form above subduction zones zones

Wet melting of the Wet melting of the mantlemantle

Wet Melting of the MantleWet Melting of the Mantle

Mount Ngauruhoe, New Mount Ngauruhoe, New ZealandZealand

Classic Stratovolcano

--- 1000s of feet high.

PyroclasticPyroclasticFlowsFlows- - - - - - - - - - MayonMayon

PhilippinesPhilippines19681968- - - - -- - - - -

Hot: 600Hot: 600ooCCFast: Fast:

60 to 100 60 to 100 mphmph

Mt. Vesuvius & Pompeii, Italy AD Mt. Vesuvius & Pompeii, Italy AD 7979

Cascade Cascade Volcanic Volcanic

ArcArc ----------

Lassen PeakLassen Peak Crater Lake Crater Lake

Mt.St.Helens Mt.St.Helens

Mt. RainierMt. Rainier - - - -- - - -

Part of Pacific Part of Pacific Ring of Fire.Ring of Fire.

Mt. Saint Helens, May, 1980 Mt. Saint Helens, May, 1980 EruptionEruption

Before

After

Mount St. Helens Mount St. Helens VolcanocamVolcanocam

http://http://www.fs.fed.us/gpnf/volcanocams/mshwww.fs.fed.us/gpnf/volcanocams/msh//

Space Needle Space Needle view Seattle, WA view Seattle, WA

and Mount and Mount Rainier:Rainier:

Most dangerous Most dangerous volcano in North volcano in North

America?America?

Mount Rainier, Most dangerous Mount Rainier, Most dangerous volcano in North America?volcano in North America?

Mount Pinatubo Tectonic SettingMount Pinatubo Tectonic Setting

Volcanoes – Agents of Climate Volcanoes – Agents of Climate ChangeChange

Mount Pinatubo, Philippines 1991

Mt. Pinatubo Ash Circles the Mt. Pinatubo Ash Circles the EarthEarth

Earth’s surface cooled 1 °F for two years.

Climatic Effects of Volcanism

Volcanic particles in stratosphere interact with man-made CFC’s to destroy ozone. Particles settle out in 2-3 years, ozone layer recovers.

Volcanoes add CO2 to the atmosphere (10% of anthropogenic emissions), contributing to long-term global warming

SO2 in the stratosphere reacts with water to form sulfuric acid, which absorbs solar energy and re-radiates it into space, creating short term cooling. Sulfuric acid droplets settle out after several years

Edvard Munch’s “The Scream”

Indonesia Tectonic Setting

Indonesia Volcanoes – 130 Indonesia Volcanoes – 130 Active!Active!

Tambora, April 1815

Largest stratovolcano eruption in recorded history

1816 – year without a summer. June snow in New England, frost in July and August. Crop failure – oats from 12 cents to 92 cents. Settlers move to midwest, Mary Shelley writes Frankenstein. Famine in Europe.

Stratovolcano v. Caldera Stratovolcano v. Caldera ExplosionsExplosions

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

St Helens Tambora1815

Ystone1.2 Ma

Ystone0.6 Ma

Ystone2.2 Ma

La Garita28 Ma

St. Helens v. Caldera St. Helens v. Caldera ExplosionsExplosions

Caldera ExplosionsCaldera Explosions

Caldera – LARGE volcanic crater Caldera – LARGE volcanic crater caused by the collapse of a magma caused by the collapse of a magma chamber after a big eruptionchamber after a big eruption

Convergent margins, hotspots Convergent margins, hotspots under continentsunder continents

Wet melting of the continental Wet melting of the continental crustcrust

Inconceivably cataclysmicInconceivably cataclysmic Often called “supervolcanoes”Often called “supervolcanoes” Magma – low temperature, high Magma – low temperature, high

gas content, high viscosity, high gas content, high viscosity, high silica content = HIGHLY explosivesilica content = HIGHLY explosive

““Nice” Caldera – KilaueaNice” Caldera – Kilauea

Wet Melting of the Continental Wet Melting of the Continental CrustCrust

CalderasCalderas Often Often

formed by formed by explosive explosive eruption.eruption.

Crater Lake fills Crater Lake fills caldera formed caldera formed by collapse by collapse during massive during massive eruption eruption of Mt. Mazama of Mt. Mazama 6600 years ago.6600 years ago.

Caldera FormationCaldera Formation

Figure 7.12: Sequence of events in the formation of Crater Lake.

Eruption Collapse

Last Big One – 74 Ka, Toba, SumatraLast Big One – 74 Ka, Toba, Sumatra

2,800 cubic kilometers of material 2,800 cubic kilometers of material ejectedejected

Cause of the human genetic Cause of the human genetic bottleneck?bottleneck?

Long Valley Caldera, Long Valley Caldera, California California - A very dangerous - A very dangerous

volcanovolcanohttp://http://

quake.wr.usgs.gov/recenteqs/Maps/Long_Valley.hquake.wr.usgs.gov/recenteqs/Maps/Long_Valley.htmltml

Right: Lasers monitor ground swelling at Long

Valley Caldera

Left: Cross section of Long Valley Caldera.

Hot Spot VolcanismHot Spot Volcanism

YellowstoneYellowstoneHot SpotHot Spot

Yellowstone Hotspot Yellowstone Hotspot VolcanoesVolcanoes

Go to the Movie

Internal Heat Generation

Earth

Remnant heat from formation, much of which is stored in the liquid core

Decay of radioactive elements

Satellites of large planets

Gravitational energy turned into heat – “tidal friction”

Io – Most Io – Most Volcanically Active Volcanically Active Spot in the Solar Spot in the Solar

SystemSystem

Io v. Titan

Io – moon of Jupiter

Sulfur / silicate magma

Titan – moon of Saturn

Ammonia-water solution magma

Igneous Rock Bodies

Small ones

Sill – horizontal tabular body

Dike – vertical tabular body

Volcanic neck – pipelike remains of a vent

Big ones

Pluton – large igneous intrusion

Batholith – really large igneous intrusion

Igneous Rock Igneous Rock Bodies Bodies

Figure 7.15 on page 148 of The Blue Planet

Igneous intrusive Igneous intrusive landformslandforms

Plutons and Batholiths: Large igneous intrusive rock bodies.Crystallized deep within crust. Exposed by uplift and erosion.

QuickTime™ and aPhoto - JPEG decompressor

are needed to see this picture.

Sills

Dikes

Volcanic Necks

Igneous intrusive rocks formed

close to surface: Dikes, Sills,

Volcanic Necks

Beneficial Aspects of Volcanoes

Outgassing formed oceans, atmosphere

Ash produces rich, fertile soil

Mineral deposits

Geothermal energy

Beautiful sunsets!

Geyser, New Geyser, New ZealandZealand

Water circulates through cooling magma bodies.Water circulates through cooling magma bodies.

Hot brines Hot brines

deposit deposit minerals minerals

with with copper, copper,

lead, zinc, lead, zinc, gold, gold, silver.silver.

Gold & Quartz Gold & Quartz VeinsVeins

Deposited in fractures by hot water (50 to 200 Deposited in fractures by hot water (50 to 200 ooC).C).

gold

quartz

Volcanic Hazards

Ash falls – choke people, animals, kill animals that eat it, collapse roofs – worsened by rain

Pyroclastic flows – suffocation and burning, knock over anything in their way

Mudflows (lahars) – ice and snow melt, rain on ash flow

Volcanic landslide

Lava flow

Poisonous gas emission – Lake Nyos in Cameroon, 1700 CO2 suffocation deaths

http://perso.wanadoo.fr/mhalb/nyos/webcam.htm

Igneous Rocks Tell Their Story

Just as sedimentary strata record the environments of their deposition, igneous rock bodies and layers record the history of magmatism and volcanism in and on the Earth. Rock types and rock distribution tell what kind of activity occurred and radioisotopic dating tells when