is erosion by lava important on mars? · 2017-11-17 · conclusions erosion by lava is possible....
TRANSCRIPT
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U.S. Department of the Interior
U.S. Geological Survey
Laszlo Keszthelyi (Kestay), Colin Dundas, Windy
Jaeger
Is Erosion by Lava Important on Mars?
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Outline
Is erosion by lava even possible?
If so, are the primary physics of aqueous and
lava floods different?
If not, how are we going to tell their channels
apart?
• Consilience: geologic context, transition zones,
etc.
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Erosion by lava happens on Mercury
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Erosion by lava happens on Venus
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Erosion by lava on the Moon
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Erosion by lava on the Earth
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But on Mars it is controversial
There is a real bias to call upon water…
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Aqueous or Volcanic?
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How to we distinguish fluvial and volcanic channels?
We (sort of) know how to distinguish
erosional fluvial channels from constructional
volcanic channels…
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Clearly Aqueous
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Clearly Volcanic
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How to we distinguish fluvial and volcanic channels on Mars?
Much harder to differentiate channels formed
by turbulent floods
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Physics of turbulent lava flows
Much harder to differentiate channels formed
by turbulent floods
• In turbulence, Re (rvL/h) is what matters
• It does take a greater L for lava to go turbulent
• For a given L, lava will have a lower Re
Recent studies suggest erosivity controlled
by Shields Number
t* = t/(Dr g D)
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Physics of turbulent lava flows
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What about thermal erosion?
Melting the substrate takes time – rate limited
by conducting heat into cold ground
Cataldo et
al. 2014
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How to we distinguish fluvial and volcanic channels on Mars?
Scale and style of
major erosion should
be identical
Can’t be eroded by
lava if there is no lava
– but there can be
draping lava
Key may be secondary
features…
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How to we distinguish fluvial and volcanic channels on Mars?
Lava should not create
m-scale erosion
channels
Lava should not create
bedload features
(dunes, bars, deltas)
because rocks stay in
suspension
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Examples: Kasei Valles
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Examples: Kasei Valles
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Examples: Hurwitz et al 2010
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Examples: Hurwitz et al 2010
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Examples: Rilles
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Examples: Athabasca Valles
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Conclusions
Erosion by lava is possible.
The primary erosion by aqueous and lava
floods should be very similar.
We can identify the erosive fluid when we can
observe secondary features.
There are many good examples of erosion by
lava on Mars.
There are many places that require further
study.