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Landforms associated w/water 2 (Characteristics Outflow Channels (Contain…
Landforms associated w/water 2
Characteristics Outflow Channels
Contain
beforms
diagnostic of fluid flow i.e. scour marks
Large forms
up to 100 km across & several 100 km long
Northern Lowlands
Most originate in 'chaotic terrain
' - collapsed zones
Single channels which shallow & narrow downstream
Giant longitudinal grooves
in some
Residual streamlined 'islands'
Megaripples
Evidence catastrophic flooding
Anastomosing channels
Regular bedforms (wavelength ~ 60m)
Abandoned spillway
Smooth Northern Plains
Signature of ancient ocean ?
Inferred periodically occupied by water body 'Oceanus Borealis'
Origin debated
Impacts release groundwater which travels to ocean?
2 Major
Valley Types
Longitudinal Valley
relatively wide & elongate
few tributaries
dissect upland plateaus
amphitheatre-like heads
gwater seepage undermines slopes
Network valleys
widen & deepen downstream
small relict river channels obscured by aeolian deposit mantle
valley termini deposits commonly lacking
lower drainage density
vs Earth?
suggest rainfall / runoff processes may not be cause
later findings suggest higher density thus role of precip
Sinous channels
meander cutoffs, scroll topog
alluvial river features
alluvial rivers flow over beds comprising material they transport
inverted relief
aeolian deflation selectively removes fine sediments of adjacent floodplains?
coarse grained channel deposits remain
meander patterns
deposition fine sediments flocculated by dissolved salts
Outflow Channels
Largest fluvial channels of solar system
e.g. Kasei,
Maja ..
Immense collapse of blocky fractured terrains at heads
Macroscale forms
scale controlled by channel flow width
developed by erosion/deposition during cataclysmic floods
erosional
scoured surfaces
channel anastomosis
low sinuosity & high width channel
streamlined residual hills
depositional
bars
fan complexes
Mesoscale forms
cataracts
longitudinal grooves
Cataclysmic flooding explanation favoured
Volcanic-induced melt of ground ice ?
Larger estimated megaflood discharge vs Scabblands
poss source of immense water discharge
Uzboi–Ladon–Margaritifer System
Cataclysmic flood channels & palaeo-fluvial/ ---lacustrine features connected
Great 800 km chain
Fed through breached impact basins
Connect Southern impact basins to Northern Plains Mars
Akin to palaeolake & channels in Asia from deglaciation
Possible Megaflood Causes
Volcanic-induced melt of ground ice ?
Pressurised flow through porous media
Magmatic intrusion & crysophere melt
Lake drainage
Liquefaction sensitive sediments
Catastrophic gas hydrate dissociation
Meteor impact into ground ice
Possible Tsunami
Metorite impact trigger for tsunami
Lobate debris deposits in Arabia Terra
along proposed palaeoshoreline of former N Ocean
Suggests ocean existed as recent as 3 Ga
Buried outflow channels
suggest catastrophic flooding in past 50 Myr
Elysium planitia