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Volcanoes on Earth and Mars:
A Comparative Study
Joseph C. KoleckiNASA/GRC/LTP
Pre-Conference Activities
1.Think about how new ideas are generated. Is there merit to saying that we establish or express “new ideas” in terms of what we already know?
2.How does describing “new ideas” in terms of what we already know apply in mathematics? In science? In your daily life?
3.Using your answers from #1 and #2 above, write out a possible definition for, “Comparative Planetology.”
4. If you were studying a newly discovered phenomenon on Mars, what basis would you use for developing your understanding?
5. For the philosophers in the group: Given that “new ideas” are expressed in terms of what we already know, is there really anything new under the sun? How did the most ancient people understand their world? In other words: What did THEY know that they could use as a basis for building new ideas? (Hint: What do many of the constellations have in common?)
6. Use a dictionary or on-line resource to acquaint yourself with the words and terms associated with volcanoes. Write out a list of words and their [brief] definitions.
7. Have all of your material from #1 through #6 ready and at hand for our videoconference!
Intro to Terrestrial Volcanoes
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Inner Core
Outer Core
Mantle (Inner and Outer)
Crust (NOT to scale!!!)
Earth’s Inner Structure
Earth’s crust is to Earth
more like
the Skin of a Baseball is to a Baseball!
A Matter of Scale
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Approximate Depths from the Surface
~30 km (~ 18 miles)
~2,900 km (~1,800 miles)
~ 5,200 km (~ 3,000 miles)
~ 6,400 km (~ 4,000 miles)
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More Info!
SurfaceTemperature ~ 0 C
Mohorovicic DiscontinuityTemperature ~ 1,000 C
Gutenberg Discontinuity Temperature ~ 3,700 C
Outer/Inner CoreBoundaryTemperature ~ 4,300 C
Inner CoreTemperature ~ 5,000 – 7,000 CT/(time) ~ 500 C/(3B Years)
Rocky
PlasticMg, Fe, Al, Si, O
Liquid Fe, S
Solid Fe
Radioactivity in the core Keeps things warm!
Ocean OceanContinental Shelf
TrenchAbyssal FloorContinental Massif
Mohorovicic Discontinuiry
Plate Movement
Upper Crust (Granite (SIMA))
Lower Crust (Basalt (SIAL))
Intro to Plate Tectonics
Upper Mantle (Aesthenosphere)
Melt Zone
Plate Movement
Subduction
Subduction
Upwelling
Subduction
Mantle Convection
Reminder: The Mantle is in a PLASTIC state!
Plate BoundaryActive Volcanism
Period ~ 200,000 years
Alfred Wegner(1881-1930)
Tell-Tale Features!
Pacific Ring of Fire
Pacific Ring of Fire…
Pacific Plate…and Present-Day Intraplate
Hotspots
Introduction to Volcanoes
Composite Volcano
High Viscosity Lava with Pyroclastic Materials
Composite
Volcanoes
Mt. Saint Helens
Mt. Shasta
Mt Rainier
Shield VolcanoHawaiian Island-TypeLow Viscosity Lava
Two Types: AA and Pahoehoe
Haleakala (showing young cinder cones in
foreground)
Hualalai
Mauna Loa
Mauna Kea
Hawaiian
Shield
Volcanoes
Ocean
Plate Movement
Intro to “Line” Volcanoes
Presently Active Volcano with Side Vent
Earlier (Now Extinct) Volcano
Act
ive
Ven
t
Old
Pip
e
Mantle Plume – “Intraplate” Hotspot
Plate Movement
Mantle Plumes – Real or Fiction?
Intraplate Hotspots
Core
Mantle
MantleM
antle
Plume
Plu
me
Plume
Hotspot
Line Islands in the Pacific Ocean
Plate Movement
Plate M
ovem
ent
Change in P
late
Directio
n
Younger IslandsYoungest Island
Old
er Island
s
FixedHotspot
(Mantle Plume)
Line Island Formation
Mohorovicic Discontinuity
Intro to Mars
Core ismost likely
Ironand
Iron Sulfide
~ 80 km (S. Hemisphere, MGS)
~ 1,500 km (MGS)
~ 35 km (N. Hemisphere, MGS)
Mantle may be in plastic state.
Crust is of variable
thickness.
MARS’ INTERIOR
Maps and Photos
Martian Shields: The Tharsis Area(Mons or Montes: Shield – comparable to Hawaiian Islands)
Olympus Mons
Martian Shield Volcano – Olympus Mons
Largest Known Shield Volcano
Anywhere in the Solar System!!!
Kilauea & Halemaumau, Hawaii
Olympus Mons, Mars
Comparing
Calderas!
Halemaumau Crater, Hawaii (Oblique View)
Olymous Mons, Mars(Oblique View – JPL)
Another angle on
Comparing
Calderas!
Some Theories of Formation
Tectonics
Asteroid ImpactHemispheric Bulge
Hellas-Tharsis?
Martian M
agnetism?
Let’s Think!1. Mars is 1/2 the size of Earth. Therefore it has 1/4 the
surface area and 1/8 the volume.
2. Heat is contained in the volume but lost through the surface. Since Mars has 1/8 the volume, what might you guess about the amount of initial heat it had?
3. The surface to volume ratio of Mars is twice that of Earth (1/4 divided by 1/8 = 2). What does this suggest about its initial rate of heat loss?
4. Given that Mars began life with a molten interior, what would you expect the interior to be like today?
5. Do you think that Mars has mantle convection and hotspots like Earth? Do you think that it could have?
Cou
ld li
near
Tha
rsis
feat
ures
be
due
to
pass
age
over
a
hots
pot?
Olympus Mons
Arsia Mons
Pavonis Mons
Ascraeus Mons
Thar
sis
Mon
tes
Tharsis
6. If there WAS motion over a hotspot, then there must have been a hotspot to move over AND the crust must actually have moved. What additional evidence would you look for to establish crustal motion?
Planetary Magnetic FieldsMars (Top)Earth (Bottom)
Striations: Earth, Atlantic Sea FloorPeriod ~ 200,000 years
Striations: Mars, Southern HighlandsStriations!
7. OK. We’ve made a good case! But is it the only possibility? Suppose we took a look at the planet as a whole: might other possibilities arise?
Hellas
Tharsis
Another Approach:
Could there be a relationship
between Hellas and Tharsis?
N
Tarsus
A Day to Remember!
8. OK. Now we’ve learned a little about Tharsis. But is this the only volcanic feature on Mars?
Other Volcanic Sites
Other Types of Martian Volcanoes
(Patera: Collapsed Shield) (Tholus: Composite)
Ceraunius andUranius Tholi
Tharsis Tholus
Tyrrhena PateraUlysses Patera Uranius Patera
Appolinaris Patera
1 2
3
654
TEST:
One of these is not like the others! Can you guess which?
Post Conference Activities1.Having been introduced to terrestrial and Martian
volcanoes, determine what terrestrial volcanoes tell us about the natural history of the Earth. Extend these ideas to speculate about the natural history of Mars.
2.Volcanoes are not the only prominent feature on Mars; there are also plains, basins, arroyos, craters, terraces, frozen poles, and myriad other features. Make a table showing correspondences between these different varieties of features on Mars with similar features on the Earth and/or our Moon. (Can the Moon be used as a source of information in comparative planetology?)
3.How did you picture Mars prior to making this study? How have your impressions of Mars been changed? (For example, does it appear more dynamic to you now than before?)
4.What expectations does this study excite for studies of other planets in the solar system? How would you study a planet such as Jupiter, a gas giant with no apparent solid surface? Would Earth be a good model for comparison here? What aspects of the Earth might be most relevant?
5.Finally, what have you learned about the way science operates? Do you believe that scientists routinely go from hypothesis to conclusion? Or is the path they follow more complex?