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Gaia Stucky de QuayBasins Research Group (BRG)Imperial College [email protected]
Landslides on Mars: Evidence of ancient glaciers?
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Landslides on Mars: Evidence of ancient glaciers?
Sub-surfaceVegetationSoilGroundwater
Human activityConstructionBlastingDeforestation
Active TectonicsVolcanicEarthquakesLiquefaction
Dynamic climateRivers/OceanSnow/RainErosion
10 km
2 km
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Structure
Background
PART I: Building a landslide catalogue
PART II: In-depth study of small-scale failure
Introduction
Summary
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Background & Literature
Introduction
Sharp, 1973 (Mariner 9)
Google Earth (CTX)
Valles Marineris(4000 km long)
Grand canyon 18 miles wide, 1 mile deep
Blocky/hummock
y
Longitudinal ridges
Massive runout/volume
WET
DRYvs.
Emplacement?
Comparison to terrestrial processes
Sherman Landslide, Alaska(1966)
Morphology?
Sliding on a cushion of steamLubricated by debris/air Dispersive grain flow
Bulk fluidizationBasal lubrication
Ground iceSurface iceSubaqueous (lacustrine)Groundwater
Melting ice lenses Debris flowOrigin?
Marsquakes & increased shear stresses
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PART I: Building a landslide catalogue1. Past and current catalogues (10-103)
2. Data and methodology
1. Program: ArcGIS + Google Earth2. Data: CTX (5m/px) + HRSC (13m/px)
wiwf
ADAS
T
D
EH
EB RD
LRLD Wc
(x,y)
3. Morphometric variablesWhat to measure?
Introduction
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Catalog Results: Maps and variablesMap of 255 landslides in Valles Marineris (complete for landslides A > 0.42 km2)
Population density
Logarithmic sizes!
Introduction
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Variable distribution: Runout & mobility
Factors affecting distribution?-Canyon width-Geology-Fluvial/glacial/periglacial/hydrothermalprocesses
Introduction
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Long runouts: H/L vs. Volume plot
High fluidization
Martian
Terrestrial
Icy/glacial
-Distinct behavioral groups
-Slope and position of saturated flows is v. different
-Martian data scattered-Seems to fit more closely to terrestrial avalanche
-However, break in slope at much larger volumes...
-What could this mean?Enhanced fluidization due to size
Introduction
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Age vs. Size: Enhanced (ancient) fluidization?
Landslide ages as measured by Quantin et al. (2004)
-Small landslides appear at all ages-Larger landslides are more frequent in the past(bounded by red line)
-If larger landslides = more fluidized, andlarger landslides = older, then it follows thatolder landslides = more fluidized
Landslide emplacement not uniform in time!
Introduction
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PART II: In-depth study of failure
Geological setting
Volumes & ages
Terrestrial analogs
Topographical analysisEmplacemen
t models
Build a 3D Digital Terrain
Model(DTM)
Now that we have an understanding of Martian landslides on a planetary scale...
CTX Image G02_019178_1717 (20m/px) Introduction
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Geological Setting
Simple relative timeline:
1. Formation of trough
2. On-going rifting (normal faulting)
3. Hydrous conditions (channels) both on plateau and canyon floor
4. Landslides occurred (synchronously?)
5. Wind erosion (yardang, inverted channels, aeolian deposits in depressions)
Introduction
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Volume and Ages
1 Ga
100 Ma
75.2+ -7.17.1 Ma
East Landslide, area=3.8x100 km2111 craters, N(1)=3.6x100 km-2
CF: Mars, Hartmann & Neukum (2001)PF: Mars, Ivanov (2001)Epochs: Mars, Michael (2013)
10-3 10-2 10-1 100 101Diameter, km
10-4
10-3
10-2
10-1
100
101
102
Cum
ulativ
e cr
ater
freq
uenc
y, km
-2
1. Surface/volume changes 2. Crater counting
Vf = 1.29 km3, 1.37 km3Vi = 2.1 km3, 5.4 km339-75% mass deficit
Can compare deposit volume (1) to the slope volume (2)
(1)
(2)
Introduction
Porosity in landslide source = ice reservoir?Age = Amazonian
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Terrestrial Analogues I: Glacier Bay, 2014February 16th, Alaska (2014)
Main differences:Thickness: 200 m vs. 13mFloor topographyWall slope (30 to 0 vs. constant 14)Snow and ice-capped terrain (vs. traveling on rock)Uneven martian floorHeight of fall (m vs. km)
Introduction
H/L = 0.27 (M), 0.22 (GB)
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primary flow lobe
longitudinal ridges
secondary flow lobe
primary flow lobe
spreading spreading
a) Martian west landslide b) Glacier Bay landslide (2014)
accumulated deposits
Terrestrial Analogues I
Longitudinal ridges are a classic glacial/Alaskan failure feature (very rarely occur elsewhere on Earth)
Exist in ~ 55% of Martian landslides
Shear velocities + basal lubrication: need a soft base and viscous layer(De Blasio 2014)
Introduction
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Topography Analysis
What could have shaped these 3 distinct features (on both deposits)?
Introduction
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Emplacement models: Deglaciation faulting
Introduction
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Emplacement models: Debris detachment
Introduction
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Emplacement models: Basal Scouring
Introduction
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Glaciation Evidence: GCMs and Landforms
Introduction
Net surface gain of ice over a year (mm) [Madeleine et al. 2009]
1. Obliquity and Climate models
2. Geomorphological systems and landforms
Proposed extent of glaciation and supraglacial landslide[Gourronc et al. 2013]
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Summary
PART I: Catalogue & large-scale
landslide statistics
PART II: DTM and small-scale landslide
features
1. Variety of scales/frequencies/formations2. Driving forces must exceed geological control3. Larger/mobile events in wider canyons4. Favorable conditions in these areas (volatiles)5. Larger landslides have larger mobilities6. These could be much older and suggest a more fluidized past (ie. glacial environment)
1. Ages places the landslides around 75 Mya2. Volume shows 3/4 of material could have contained ice3. Comparison to Glacier Bay shows very similar features4. Topographic analysis shows 3 distinct structures on both slides(relying on a soft, low-friction, widespread and transient layer)5. Emplacement models with ice can explain these6. Glaciation in Valles Marineris is supported both by geological evidence and GCMs
Introduction
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Next steps...
Introduction
