Faculty of Geosciences
Research group
River and delta morphodynamics
Faculty of Geosciences
Martianv
IntroductIon
• There are many channels on
Mars, but climate conditions were different than on Earth.
• Different sources of water have been
proposed for Mars, including groundwater as main source for channel formation [1,2,3].
AIms
• Knowledge on groundwater-
induced channels is minimal due to limited occurence on Earth.
• We aim to extend the knowledge on related processes and resulting morphology for these systems from scaled flume experiments.
References [1] Howard A.D. & McLane C.F. (1988) WRR 24(1), 1659-1674. [2] Kite E.S. et al. (2011) JGR 116, E07002. [3] Andrews- Hanna J.C. & Phillips R.J. (2007) JGR 112, E08001. Image credits HiRISE: NASA/JPL/University of Arizona, THEMIS: NASA/JPL/
ASU. Funding WAM is supported by NWO grant ALW-GO-PL/10-01 to MGK.
Wouter marra
Martian Groundwater Outflows in Flume Experiments Processes and Morphological Properties
Wouter A. mArrA1 & m.G. KleInhAns1 (in collaboration with: e. hAuber2, d.P. PArsons3, s.J. conWAy4, s.J. mclellAnd3 & b.J. murPhy3)
1Fac. of Geosciences, Utrecht University, the Netherlands, w.a.marra@uu.nl; 2Institute of Planetary Research - DLR Berlin, Germany;
3Dep. of Geography Environment and Earth Sciences, University of Hull, United Kingdom; 4Dep. of Physical Sciences, The Open University, Milton Keynes, United Kingdom.
exPerIment movIes http://goo.gl/gfUbO
dIstAnt sourcelocAl InfIltrAtIon
Ground WA ter sAPPI n G
sub-lIthostAtIc PressuresuPer-lIthostAtIc PressurePressur Ized Ground WA ter
exPerIment setuP eArly stAGe morPholoGy fInAl morPholoGy shAded dem mArs looK-AlIKe Key feAtures
41°30'W 42°W
42°30'W 43°W
43°30'W
1°N0°30'N0°0°30'S1°S1°30'S
25 km
¯
54°30'W 9°S9°30'S10°S 55°W
10km
¯
157°13'35"E 157°13'30"E
157°13'25"E
10°16'15"N10°16'10"N10°16'5"N
50 m
¯
80°30'W 81°W
0°30'S1°S1°30'S
10 km
¯
6 m Cross-section
Plan view
4 m 1.2 m fake floor
valley
unsaturated sediment
subsurface source Discharge
~ 25 l / min
surface runoff seepage zone
subsurface source
lobe seepage
zone
6 m Cross section
Plan view
4 m 1.2 m fake floor
valley
unsaturated sediment
subsurface source Discharge
~ 75 l / min
surface runoff
lobe
pitspits bulge
6 m Cross-section
Plan view
4 m 1.2 m fake floor
seepage zone saturated sediment
Discharge ~ 10 l / min
valleys headward
development similar development for all valleys Rain simulator
(rain simulator above entire reach) 6 m Cross-section
Plan view
4 m 1.2 m fake floor
seepage zone unsaturated sediment
saturated sediment
constant head tank
Discharge ~ 2.4 l / min
headward
development valleys
groundwater piracy
small valleys cease to develop
• Different sizes of valleys due to flow piracy.
• Theater-shaped valley heads due to mass
wasting processes.
• Valley depth relates to groundwater level.
- Further developed valleys are deeper as groundwater level is deeper upstream.
• Several valleys similar in size, due to absence of flow piracy.
• Headward development by mass wasting.
• Shallow valleys, due to high groundwater level.
• Simulated in experiment as precipitation, but
could be melt of snow or subsurface ice.
• Converging flow features upstream: feather-
shaped head.
• Deposition of lobes after first overflow due to
infiltration in unsaturated substrate (sieve deposits).
• No morphology left by actual seepage process.
• Not found on Mars without pits or chaos (see next).
• Similar features as sub- lithostatic pressure, but:
• Cracks and breaking of surface due to super- lithostatic pressure.
• Pits in source area carved by emerging groundwater.
• Converging flow
features disconnected from source area.
~ 1 m ~ 1 m
~ 1 m ~ 1 m
~ 0.5 m ~ 0.5 m
~ 0.5 m ~ 1 m
themIs daytime Ir mosaic
hirIse PsP_007843_1905
themIs daytime Ir mosaic
seepage zone
flow unsaturated
sediment
flow
flow
flow surface
runof
f Infiltration
seepage at heads mass-wasting
fluvial transport
seepage
zone slope
Quick Incision
sediment uplift slope
Pit formation
converging flow features
terraces
lobate deposits
converging flow
Pits
lobes
steep amphi-theater shaped head
shallow valleys terraces
shallow amphi-theater shaped heads
faded boundaries
flat floors
chaotization?
equal-sized amphi-theater shaped heads
Joining of valleys downstream
Amphi-theater headed val- leys in different sizes
elongated pit converging
flow runtime: 3 days
runtime: 1 hour
runtime: 1 hour
runtime: 15 minutes
converging flow
classic examples have disturbed source, not found without chaos or pits yet.
morPholoGIcAl AnAlysIs (SaPPING ONLy)
• Sapping valleys fed by distal
groundwater source are deeper and have more pronounced
valley heads (Fig. 1).
• In both cases, valleys are steeper in the upstream part (Fig. 2). This
relates to the difference in processes:
mudflows in the upstream end, fluvial transport downstream.
• Valleys become more U-shaped when they develop (Fig. 3). Valleys fed by
distal groundwater have a higher shape index, as the valleys have steeper cliffs.
conclusIons
• Different sources of groundwater for channel formation produce distinct types of valleys and channels.
• Groundwater sapping:
- Produces theater-shaped valley heads.
- Flow piracy occurs when the water source is distal, this focusses flow and enhances development of a few channels.
- Two processes, mudflow and fluvial flow are shown by a break in slope.
- Erosion takes place in pulses due to the collapsing development.
• Pressurized groundwater release:
- Results in channel head with converging flow features.
- Downstream lobate deposits on unsaturated sediment.
- Super-lithostatic pressure breaks surface and forms pits in the source area.
morPholoGIcAl develoPment (SaPPING ONLy)
• Valleys become wider, deeper and longer during the experiments.
- In the distal cases, widening slows as valleys develop
(Fig. 4a). In the
local case (Fig. 5a), the rate remains fairly constant.
- Valley lengthening slows in both types of experiments
(Fig. 4b, 5b).
• Erosion takes place in pulses, which are more sudden in the distal
cases (Fig. 4d) due to the collapsing nature of the headward development and widening.
• In the distal experiments, the
number of active valleys decreased, due to groundwater piracy.
0 12 24 36 48 60 72
0 100 200 300
Time (hours)
Cumm. erosion (kg)
e Calculated Measured
0 0.5 1 1.5 2
Erosion rate, E (g s−1 ) 0 d
0.1 0.2
Valley depth (m)
c 0
1 2
Valley length (m)
0 b 0.2 0.4 0.6
Valley width (m)
a
C E J other
0 20 40 60 80
0 100 200 300
Time (minutes)
Cumm. erosion (kg)
e Calculated Measured
0 5 10 15 20
Erosion rate, E (g s−1 ) 0 d
0.05 0.1
Valley depth (m)
c 0
1 2 3
Valley length (m)
0 b 0.2 0.4
Valley width (m)
a
A E K N
0 0.5 1 1.5 2
−1.2
−1
−0.8
−0.6
−0.4
−0.2 0
Distal C Distal D
Distal E Local L Local N
Distance along valley (m)
Elevation (m)
Valley profile Initital surface
fig. 1 Valley profiles
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45
D up D dwn L up L dwn
slope (m/m) Si
0 0.5 1 1.5 2 2.5
.5 1/4 pi 1
A B
C
D
E
F G H
I
J
BA C D
E
F H IG J
K
M L N
Valley length, L (m) Cross section shape index, SI c (−)
Distal Local
fig. 2 Valley slopes fig. 3 Valley shapes
fig. 4 Morphological development distal sapping experiments.
fig. 5 Morphological development local sapping experiments.
methods
• Experimental setup consists of a flume of 6 m long x 4 m wide and 1.20 m deep.
• Simulation of seepage from sub-
surface groundwater level from a distant source using a constant head tank.
• Seepage from a local source (e.g. melt or
precipitation) was simulated by rain simulators.
• Pressurized aquifer release using a subsurface drainage pipe with forced discharge, at:
- sub-lithostatic pressure (only seepage) - super-lithostatic pressure (sediment
lifted by water pressure)
• Data: time-lapse imagery and laserscan DEMs.
themIs daytime Ir mosaic
0.16 0.12 0.08 0.04 0
Erosion (m)
A
J e
G h
f I
d c
b
m K l
J h I
f G e
c d A b
n
1 m
1 m
1 m
1 m
