landslides on mars: evidence for ancient glaciation? (apex seminar)
DESCRIPTION
Landslides have been mapped within the large Valles Marineris canyon on Mars. These large deposits can provide hints as to Mars' past climatic history, and can help us understand the role of ice and water on the red planet.TRANSCRIPT
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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