Transcript 9.4 Extraterrestrial Vulcanism

“Fires that shook me once,
but now to silent ashes
fall'n away. Cold upon
the dead volcano sleeps
the gleam of dying day.”
-Tennyson
Volcano Types:
Cinder-cone: Small, steep, ejected material returns.
Shield Cone: Circular base, gentle slopes, basaltic, non-explosive.
Composite Cone: Large, explosive, fragments plus lava.
Past Volcanism on Mercury
Abundance of surface craters
No craters more that 50 km in diameter
Evidence of lava-filled craters
Volcanic rock samples predate Earth
Rock samples dated @ >3000 million years ago
Volcanic Activity on Venus
80% of the planet’s surface shows volcanic activity
Several million volcanoes have been detected
Venus is (debatably) volcanically extinct
Many volcanoes are several hundred km across, and
thousands of km high
NASA Photo: A Volcano on Venus
Largest volcanoes are shield-cone type
No plate tectonics, which is part of how Earth cools
Unconfirmed cooling theories: hot spot volcanism
and/or bubbling, blistering surface volcanoes
Terrestrial
Volcanism is a separate
topic not covered here; please refer to
your textbook, the internet, or other
relevant Earth-science resources.
The Moon
The dark spots on the
moon (maria) are large
depressions covered with basaltic lava
flows, the result of volcanic activity that
began over 3 billions years ago!

Martian Volcanoes
Mars is almost volcanically extinct; this is debatable
Martian volcanoes are probably all shield-cone types
Mars has at least 3 volcanoes larger than those on Earth
Mars has the largest volcano in the solar system:
Olympus Mons
Olympus Mons:
A Shield Volcano
on Mars
Earth’s Largest Volcano: Mauna Loa
9 km high
120 km across
x 3=
Olympus Mons:
24 km high
550 km across
Mars ≈ 1/2 of Earth’s diameter
Olympus Mons ≈ 3 times the size of Earth’s largest Volcano
Huge size disparity due to Mars’ stationary crust, hence
enormous hot-spots that build-up in stationary positions
Volcanoes on Io:
A moon of Jupiter
The most volcanically active place in the solar system
At least 8 active volcanoes have been mapped
Plumes extend ≈ 280 km above Io’s surface
Molten rock spews out faster than the speed of sound
The size of Io is ≈ Earth’s moon
Jupiter ≈ 318 times more massive than Earth itself
Io and Earth’s moon ≈ same orbit, but Io has greater
gravitational stress, causing huge amounts of internal heat
Io: One of Jupiter’s Moons
Io:
Images from Galileo’s Mission
(“Raw” images)
(Digitally remastered)
Volcanoes on Other Moons of Jupiter:
Europa and Ganymede have “Cryovolcanism!”
Triton:
The seventh
(and largest)
of Neptune’s
Moons also
features
“Ice Volcanoes!”
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Triton is the only large moon with a retrograde orbit
Temperature equals Pluto’s ≈ -235ºC
Surface contains only a few craters
The surface is young; older features destroyed
Ice Volcanoes! Liquid Nitrogen??
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
?
Scientists continue to search for evidence
of extraterrestrial volcanism……
Websites Used for Research can be found at:
www.deafscience.net
under the “Astronomy” category