Volcanoes on Earth and Mars: A Comparative Study Joseph C. Kolecki NASA/GRC/LTP

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

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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?

joseph.c.kolecki@nasa.gov