Download Vulcanism on Venus

Vulcanism on Venus
Venusian Structure
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Iron-Nickel rich core
Mantle composed of
magnesium-rich
silicates and oxides
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Basaltic crust
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Venera 13 & 14
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Tholeiitic basalt
Tesserae
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From latin word for
Tile
Covers 10% of
surface
Result of crustal
compression
through tectonic
activity
This region covering an area
of 37 by 80 km , located at
30N 333E on the low rise
separating Sedna Planitia and
Guinivere Planitia
Venus Surface
Volcanic Structures
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Large Volcanoes
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Small Volcanoes
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Lava flows
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Lava Channels
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Calderas
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Coronae
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Novae
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Arachnoids
The global distribution of volcanic features on Venus. NASA.
Shield Volcanoes
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More than 150 large
shields
Upland regions
Gentle slopes, long
radial flows
Central vent or
summit caldera
The global distribution of large shield volcanoes on Venus. Each
red triangle marks the site of a shield volcano over 100 km in
size. NASA.
Sapas Mons, near the equator in Atla Regio
Magellan Press Release Image P-38360, JPL
image MGN-51
Ushas Mons, on the northern part of Dione
Regio
Magellan Press Release Image P-42386, JPL
image MGN-117
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Viscous, silicate rich lava
flows
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''pancake'' domes
Little evidence of
explosive eruptions
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High atmospheric pressure
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Water content in magma
Volcanic 'pancake' domes in Tinatin
Planitia, located at 15N, 9E. Nasa
Chain of pancake domes east of Alpha Regio
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Mostly in lower
elevations and on the
plains
''anemone'' shields
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Central vent, lava
flows
''tick'' volcano
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Raised rim, radial
ridges
The global distribution of small shield volcanoes (ranging between 20
and 100 km across), small shield fields and volcanoes with ‘anemone’
(flower-like) patterns of lava flow. NASA.
Venusian 'tick' volcano, diameter 30 km
20S, 3E NASA
Venusian 'anemone' shield, 10S, 201E
NASA
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Cones
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Mainly circular, steep slopes
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Small groups on fractured
plains
A field of volcanic
cones lies on the fractured
plain of Niobe Planitia.
These cones average 2 km
wide and rise to heights of
around 200 m. NASA.
Lava flows
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80 % of lowland
plains
More than 50
Mostly around
elevated borders of
lowland plains
Streamlined islands in a
lava outflow channel in
the Ammavaru area, Lada Terra. NASA
Some show
streamlined islands
Mylitta Fluctus
Mylitta Fluctus, a large
volcanic flow field in Venus’
southern hemisphere.
NASA.
Lava Channels
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In volcanic plains
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Similar to terrestrial rivers
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Due to surface temperature and
pressure the lava stays fluid
longer
Baltis Vallis
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6800 km long
A 600 km long section of
the Solar System’s longest
lava channel, Baltis Vallis.
NASA.
A lava channel some 200 km long and 2
km wide cuts through the terrain south of
Atira Mons. NASA.
Calderas
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Large circular or
elongated
depression
Formation process
Sacajawea Patera (64N,
335E), an elliptical caldera
measuring 175 × 260 km.
Its floor lies some 2,000 m
beneath its rim. NASA.
Coronae
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Ø: 60-2000 km
Circular or oval
structures
Complex fractures
Formed because of
rising molten rock
Fotla Corona (59S, 164E), 150 km in diameter,
displays a number of ‘pancake’ volcanoes.
NASA.
Arachnoids
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Concentric
fracturing
Strong radial
faulting
Concentric
structures enclose
radial faults
=> „Spider-web“
Typical arachnoid
feature, NASA
Novae
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Lack annular
fractures
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Central dome
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Radial fracturing
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Early stage of
corona formation
This nova lies in Themis
Regio at 30S, 279E and
measures 250 km across.
NASA.
Chronology of Corona and Nova
Formation
The proposed cases for corona-nova chronology.
(Aittola et al., 2002)
Active Volcanism?
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Few impact craters => entire
surface younger than ½ billion
years
Clouds of SO2 (volcanic gas) and
many volcanoes – no active
volcanism detected
Infrared observations indicate
some regions were resurfaced
rather recently. Venus was
recently (and still may be)
volcanically active.
Radar and topography “image” from the Magellan
spacecraft of Idunn Mons on Venus, which was
recently volcanically active. Dark regions are
smooth, and bright regions are rough or steep.
Elevations have been exaggerated thirty times.
Surface Hot Spots
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Some volcanic regions have higher
emissivity than their surroundings
Lower emissivity regions have
reacted chemically with CO2 and
SO2 in the atmosphere, forming a
thin crust over the lava
High emissivity indicates younger
material that has not been
substantially weathered by Venus'
thick atmosphere
Infrared observations from the Venus Express
spacecraft overlaid on the image from the previous
slide show that Idunn Mons (red) has higher
thermal emissivity than its surroundings (blue).
This indicates a compositional difference between
the two regions.
Sources
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Venus, Peter Cattermole
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Venus and Mercury, and How to Observe Them, Peter Grego 2008
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http://volcano.oregonstate.edu/oldroot/volcanoes/planet_volcano/venus/intro.html
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http://dps.aas.org/education/dpsdisc/
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http://rst.gsfc.nasa.gov/Sect19/Sect19_9.html
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Aittola et al. 2002, Chronology of the formation process of Venusian novae and the
associated coronae
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Müller, Volcanic Structures at Venus