The Fire Within:
Plate Tectonics & Volcanism Across
the Solar System
By the Lunar and Planetary Institute
USGS Photo by B. Chouet
For Use In Teacher Workshops
What’s a Rock?
What are the Main Rock Types?
How Do They Form?
How Do You Tell One from
Another?
Igneous

All igneous rocks
cool and crystallize from magma or lava
 or consolidate from pyroclastic materials

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Magma is molten material below the
surface
Lava is molten material on the surface
Pyroclastic materials are particles such
as volcanic ash
Metamorphic

Changes in minerals, texture, and/or chemical
composition of a rock that result from changes
in temperature and pressure … like burial,
contact with hot stuff, extreme crunching …

No melting!
Photo by J.P. Lockwood. Figure 24-B, U.S. Geological Survey Bulletin 1595.
Sedimentary
Clastic Sedimentary Rocks
Carbonate /
Other Sedimentary Rocks
Sediment particles (skeletal, rock
fragment, mineral, plant particles)
derived from erosion (breakdown /
transport) of rock that are lithified
(cemented or compacted)
Chemical precipitates (halite) or
biologically - produced (organic)
material (shell fragments). Insitu.
Images from http://wrgis.wr.usgs.gov/parks/rxmin/rock2.html
What is the Rock Cycle?
From USGS at http://3dparks.wr.usgs.gov/nyc/images/fig6.jpg
Igneous Part of the Rock
Cycle
From USGS at http://3dparks.wr.usgs.gov/nyc/images/fig6.jpg
Igneous Rocks

All igneous rocks
cool and crystallize from magma or lava
 or consolidate from pyroclastic materials




Magma is molten material below the
surface
Lava is molten material on the surface
Pyroclastic materials are particles such
as volcanic ash
Identifying Igneous Rocks

Step 1.
Is it an igneous rock?
Interlocking randomly oriented crystals?
Published as figure 14 in U.S. Geological Survey. Bulletin 1595. 1987
Identifying Igneous Rocks

Extrusive or volcanic rocks


form at the surface from lava or
pyroclastic materials
Intrusive or plutonic rocks

form from magma in the crust
Identifying Igneous Rocks

Igneous rocks have 4 textures


determined by the cooling rate of magma or
lava
Texture

size, shape and arrangement of crystals in a
rock
4 Cooling-Rate Textures

Phaneritic – Coarse Grained (Intrusive)


Aphanitic – Fine Grained (Extrusive)


visible grains, cooled slowly
with grains too small to see, cooled quickly
Porphyritic – (Extrusive)

with larger grains surrounded by a finergrained groundmass


cooled slowly first, then more quickly
Glassy

with no grains

cooled too quickly for minerals to grow
Igneous Rock Textures

Also vesicular texture, with holes
(vesicles)


indicates the rock formed as water vapor
and other gases became trapped during
cooling of lava
Pyroclastic or fragmental texture

containing fragments formed by
consolidation of volcanic ash or other
pyroclastic material
Identifying Igneous Rocks

Step 2.
Coarse grained or fine grained?
(Porphyritic or Aphanitic)
From the USGS photo glossary of volcanic terms
Igneous Rocks

Texture and composition are the criteria
used to classify most igneous rocks

Composition categories are based on
silica content
felsic (>65% silica)
 intermediate (53-65% silica)
 mafic (45-52% silica)

Identifying Igneous Rocks

Step 3.
Light or Dark? … Composition Hints
Images from USGS Photo Library
Identifying Igneous Rocks

Step 4.
What minerals present?
Quartz – gray opaque, concoidal fracture
K-Spar - pink
Plagioclase feldspar – white to gray
Muscovite – light, flakey
Biotite – dark, flakey
Pyroxene - LBM
Amphibole - LBM
USGS Mineral Specimen Photography: Bureau of Mines, ___ and Mineral collection
of Bringham Young University Department of Geology, Provo, Utah
Igneous Rock Classification
Diagram by staff of LPI
A Classification of Igneous Rocks
Cooling History / Texture
Mafic and Dark
Color
Slow Cooling and
Coarse Grained
Fast Cooling and
Fine Grained
Gabbro
Basalt
Very Fast Cooling and
Glassy/Cellular
Scoria
Intermediate in
composition
and color
Diorite
Andesite
Felsic and Light
Color
Granite
Rhyolite
Pumice and Obsidian
Green sand beach – why green?
Image courtesy of Alison Henning, Rice University
Volcanoes!
Lassen Volcanic
National Park, CA
Image from http://photo.itc.nps.gov/storage/images/lavo/lavo-Full.00005.html
Volcanic Deposits
Shape depends
on composition
of magma…
Basaltic
Andesitic
Rhyolitic
…and gas content
… and number
and size of
eruptions
… and the
environment of
eruption
http://volcanoes.usgs.gov/Hazards/What/hazards.html
Volcanic Deposits
http://volcanoes.usgs.gov/Products/Pglossary/basalt.html
Why does silica matter?

Si - O bonds much stronger
than others

In lava, single silica tetrahedra
flow easily, like little balls
In lava, large silicate polymers
flow poorly, like noodles

Diagram by staff of LPI
Basaltic Lava

High temperature
(1000-1200 C)

Lower silica content

Extremely fluid
Images courtesy of Alison Henning, Rice University
Basaltic Lava

Flood basalts – huge
plateaus (e.g. Columbia
Plateau of Washington
and Oregon)

Pahoehoe and aa – ropy
vs. jagged blocks (e.g.
Hawaiian volcanoes)

Pillow lavas – ellipsoidal,
cool underwater
Images from USGS Photo Glossary of Volcano Terms
Rhyolitic Lava

Most felsic, light in color

Higher silica content

Lower melting point than
basalt. Erupts at 8001000 C

Moves 10 X more slowly
than basalt

Tends to be explosive –
more gas (water) content
USGS Photo Glossary of Volcano Terms
Gas Content

Magma rises close to surface,
pressure drops

Volatiles released with
explosive force

Explosive eruptions most likely
with gas-rich, viscous rhyolitic
and andesitic magmas

Pyroclasts – rock material
ejected into air
Image courtesy of Alison Henning, Rice University
Volcanic Landforms

Shield volcanoes – Mauna Loa



Big
Broad, Low Slope
Properties of lava? Number of flows? Types of rocks?
Image from http://hvo.wr.usgs.gov/maunaloa/
Volcanic Landforms

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Lava Plateau
Extensive
Stacked flows
Virtually no slope
Properties of lava? Number of flows? Type
of rock?
Photo from http://en.wikipedia.org/wiki/Image:3-Devils-grade-Moses-Coulee-Cattle-Feed-Lot-PB110016.JPG
Columbia Plateau
130,000 Km2 x 1.5
km thick
Buried topography
~16 Ma

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Cinder Cones
Small
Steep slope (30o)
Basaltic …
hmmmm
Properties of lava?
Number of flows?
Types of rocks?
USGS image
Volcanic
Landforms
USGS Photo by K. Segerstrom
NPS image from Capulin, NM

Small

Few events

Flanks of
Mauna Kea

Common on
shield volcano
flanks
USGS Photo Glossary of Volcano Terms
Volcanic Landforms


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Composite
Volcano
Big
High slope
(30o)
Made of
multiple lava
and ash flows
Explosive
USGS Photo Glossary of Volcano Terms
Properties of lava? Number of
flows? Types of rocks?
Composite Volcano - Mt St Helens
Images from http://vulcan.wr.usgs.gov/Volcanoes/MSH/SlideSet/ljt_slideset.html
Pinatubo
USGS photo by Dave Harlow
Volcanic
Landform

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

Dome
Small
Steep slope
Properties of
lava? Number of
flows? Type of
rock?
Foreshadowing … Patterns to where types
of volcanos occur?
If a planet has active volcanos,
what do we know about the planet?
NASA/JPL/NGA image from http://photojournal.jpl.nasa.gov/catalog/PIA06668
Where Does the Heat Come From?
Hubble Image from http://hubblesite.org/newscenter/archive/releases/1998/38/image/a/
Where Does the Heat
Come From?
(Terrestrial Planets)
Image by LPI
Image by LPI: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=168
Originally:

Impacts (accretion), differentiation, radioactive
decay
Presently:

Mostly radioactive decay
What Evidence Suggests
Volcanism on Other Planets?
NASA image at http://photojournal.jpl.nasa.gov/catalog/pia00254
Past
• Mercury, Venus,
Earth, Moon, Mars,
Io, Titan
Presently
Photo montage from
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=2167
• Earth, Io, Enceledus,
Triton
• Probably Venus and
Mars
What Planets Are / Have Been
Volcanically Active?
Image: Lunar and Planetary Laboratory:
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=178
Why Might a Planet Have Ceased Being
Volcanically Active?
Our Moon
What do you observe?
Image at http://www.lpi.usra.edu/education/timeline/gallery/slide_61.html
Big Impact Basins Filled by Lava
Apollo image from
Mare Imbrium
http://www.lpi.usra.edu/expmoon/Apollo15/A15_Photography_orbital.html
Volcanism after impacts – most before 3 Ga (to 1 Ga)
Fissure Eruption Courtesy of USGS.
http://www.geology.sdsu.edu/how_volcanoes_work/Thumblinks/Puuoorift_page.html
Lunar Basalts
15555
Apollo image from
http://curator.jsc.nasa.gov/lunar/compendium.cfm
15016
Apollo image at http://www.lpi.usra.edu/expmoon/Apollo15/A15_BasaltFS.gif
3.3
Billion
Years
Old
Lunar Volcanism
Aristarchus
Photo of Aristarchus Plateau at
Plateau
http://lunar.gsfc.nasa.gov/images/gallery/2Craters_br-browse.jpg
Marius http://history.nasa.gov/SP-168/section2b.htm
Hills
photo by Lunar Orbiter V at
Mercury



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Tons of Craters
Some Flat Plains …
hmmmmmm…
Only ~ 1/3 imaged
Messenger
spacecraft on its way
to orbit!
Image: http://www.lpi.usra.edu/publications/slidesets/ss_tour/slide_2.html
Craters and Plains
500 km
Mariner image at http://photojournal.jpl.nasa.gov/catalog/PIA02948
Venus
Magellan image from http://antwrp.gsfc.nasa.gov/apod/ap020330.html
Venera Images - 1982
Image: http://www.lpi.usra.edu/publications/slidesets/ss_tour/slide_5.html
Sapas Mons – 1.5 km high, 400 km across
Atla Regio
Magellan image at http://www2.jpl.nasa.gov/magellan/image28.html
Maat Mons – 8 km high,
Aphrodite Terra Region
Magellan color image at
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=2085
Courtesy of David P. Anderson (Southern Methodist University) Image at
http://www.lpi.usra.edu/publications/slidesets/venus/slide_21.html
Pancake Domes


Single Flows, Steep
sides
Height 1/2 - 1 km.


What kind of
volcano?
What kind of lava?
NASA Image from LPI: http://www.lpi.usra.edu/publications/slidesets/venus/slide_24.html
Pancake Domes


Rhyolite?
Or merely cold,
crystal-rich basalt?
USGS photo by R.A. Bailey


What kind of
volcano?
What kind of lava?
What’s missing?
Few impact craters – what does this tell us?
No craters less than 3 km (meteoroid ~ 30 m across)
Atmospheric filter
Magellan image from http://antwrp.gsfc.nasa.gov/apod/ap020330.html
Mars

dfldjfkdkfj
MOLA image from http://pds-geosciences.wustl.edu/missions/mgs/mola.html
Olympus Mons
TALLEST Volcano in the
Solar System
24 km high
550-600 km across
Mauna Loa
9 km high (sea floor)
120 km across (base)
Lava flows in last million
years?
Viking image at http://photojournal.jpl.nasa.gov/catalog/PIA02982
Mars
LPI image at http://www.lpi.usra.edu/publications/slidesets/hawaiivolcanoes/slidespages/slide_01.html
LPI image at http://www.lpi.usra.edu/publications/slidesets/redplanet2/slide_10.html
Mars


Olympus Mons
Image overlain on topography and vertically
exaggerated 10x
MOLA image at http://photojournal.jpl.nasa.gov/catalog/PIA02806
Mars Express images from
http://www.esa.int/esaMI/Mars_Express/SEMKC2W4QWD_0.html And
http://www.esa.int/esa-mmg/mmg.pl?b=b&keyword=Olympus%20Mons%203D&single=y&start=5
On Syrtis Major - Shield Volcano
USGS image at http://wrgis.wr.usgs.gov/fact-sheet/fs024-02/
Themis image at
http://themis.la.asu.edu/zoom-20030514a.html
Broken Cinder Cone?
Why Might a Planet Have Ceased Being
Volcanically Active?
Hubble
Io
NASA Gallileo Image at: http://www.lpi.usra.edu/publications/slidesets/ss_tour/slide_23.html
Io
• About the size of our
Noon
• HOT – tidal friction
• Lots of Sulfur
• Voyager detected
• Yellow-brown color
• Silicate lava – crust is
silicate in nature (strong;
supports high mountains
and deep crevasses; lava
flows at temps too high for
S)
NASA Gallileo Image at: http://www.lpi.usra.edu/publications/slidesets/ss_tour/slide_23.html
Io
Galileo Image
Tvashtar Catena
NASA Galileo image at: http://photojournal.jpl.nasa.gov/catalog/PIA02584
Io
Amirani Lava Flow – Galileo Image
Largest active flow in solar system (~200-300 km)
Galileo image from http://photojournal.jpl.nasa.gov/catalog/PIA03533
• Plumes of sulfur / sulfur
dioxide
• Long-lived (months)
• Geysers
• High – lack of
atmospheric pressure
and low gravity
• Old Faithful – 35 km
high if on Io
Voyager image at http://photojournal.jpl.nasa.gov/catalog/PIA01971
Io
New Horizons flew
past Io in late
February 2007
New Horizons photos at http://pluto.jhuapl.edu/gallery/missionPhotos/pages/022707_1.htm l