Faculty of Geosciences
Research group River and delta morphodynamics
ExpErimEnt rEsults: diffErEnt outflow procEssEs at diffErEnt prEssurEs
• Low pressure: normal seepage
• Medium pressure: fissure seepage, fissures are created by the surface
• High pressure: bulging of surface and fomation of sub-surface pressurized lake which later erupts
implications
• Groundwater flow alone does not explain the large outflow channels, the expected discharge of only seepage (fig. a) is too low.
• Fissure seepage (fig. b) is more effecive than normal seepage, but still limited by groundwater rescharge to the fissures.
• Pressurized groundwater release at high pressures induces bulging of the surface (fig. c). This subsurface reservoir is an effective
mechanism to quickly outflow large amounts of water.
introduction
• Outflow channels result from release of pressurized groundwater confined beneath a crosphere.
• A problem with this theory is that
groundwater flows slowly and outflow
channels are huge and require large amounts of water in short amounts of time.
• Knowledge on such systems in limited as such events never occur on Earth.
aims
• We want to know what groundwater outflow
mechanisms there are and if this can form these large valleys.
mEthods
• Experimental setup consists of a flume of 6 m long x 4 m wide and 1.20 m deep.
• Pressurized aquifer release using a subsurface drainage pipe with forced discharge, at:
- sub-lithostatic pressure (only seepage)
- super-lithostatic pressure (breaking of surface) - flexure inducing pressure (surface
lifted by water pressure)
• Data: time-lapse imagery and laserscan DEMs.
References Clifford, S. M., and T. J. Parker (2001), The Evolution of the Martian Hydrosphere: Implications for the Fate of a Primordial Ocean and the Current State of the Northern Plains, Icarus, 154(1), 40–79,
Funding WAM is supported by NWO grant ALW-GO-PL/10-01 to MGK.
wouter marra
Martian Groundwater Outflows in Flume Experiments
woutEr a. marra
1, w.a.marra@uu.nl
m.G. KlEinhans1, 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.
conclusions
• Pressurized groundwater release can take place as seepage, as fissure flow or through the release of a subsurface lake.
• The formation of a subsurface lake is the result of flexure of the surface.
• This mechanims may account for the largest outflow valleys on Mars.
Maja Valles source area (THEMIS IR / MOLA)
Source pits and Chaotic terrains Outflow Channel
Confining cryosphere Pressurized Aquifer
Groundwater in
Mega-regolith aquifer
Groundice
Hydraulic head
Pressurized groundwater Impermeable basement
Area of interest:
Outflow channel region
Mars during the Hesperian: confined aquifer
(After Clifford & Parker, 2001)Infiltration
~3 km
~20 km
break in slope
flat area sloping section
C
P source location
00:27:30 i
00:41:30 ii
00:49:00 iii
01:03:00 iv
01:17:30 v
Experiment 1 - Low Pressure a
00:03:10 i
00:04:30 ii
00:08:55 iii
00:12:05 iv
00:13:15 v
Experiment 2 - Medium Pressure b
00:02:15 i
00:02:50 ii
00:02:55 iii
00:05:20 iv
00:11:25 v
Experiment 3 - High Pressure c
a
b
c
Confining layer Aquifer
Pressurized lake
Groundwater / darcian flow Fissure / turbulent flow
Qseep
Qfiss
Qfiss
L A
L
t a
gutter
C1 C2
C5
C4
C6
C3
fake floor sediment
1.2 m
6 m
g b
c
g
C1 C2
C3
C6
C4 C5
4 m
6 m
LS2
LS1 LS1 LS2
punctured section
sp pp
sp
Martian
v
a
b
c
Confining layer Aquifer
Pressurized lake
Groundwater / darcian flow Fissure / turbulent flow
Qseep
Qfiss
Qfiss
L A
L a
b
c
Confining layer Aquifer
Pressurized lake
Groundwater / darcian flow Fissure / turbulent flow
Qseep
Qfiss
Qfiss
L A
L
~ 1 m
