Explosive lava-water interactions on Earth and Mars

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Volcanic rootless constructs (VRCs) are products of explosive lava–water interactions. VRCs are significant because they imply the presence of active lava flows and an underlying aqueous phase (e.g., groundwater or ice) at the time of their formation. This information is valuable for locating fossil hydrothermal systems and exploring the relationships between climate, water stability and abundance, weathering environments, and the development of habitable niches in extraterrestrial environments.

The architecture, structure, and emplacement chronology of VRCs in the 1783–1784 Laki lava flow in Iceland were investigated using tephrostratigraphy, Differential Global Positioning System (DGPS) measurements, remote sensing, and Geographic Information Systems (GIS). The geospatial distribution of rootless eruption sites were also analyzed using statistical methods to quantify their patterns of spatial organization and infer the geologic processes of their formation.

Employing terrestrially validated morphological and geospatial criteria, analogs to Icelandic VRCs were identified in the Tartarus Colles region of Mars. The VRC groups and associated geologic units were mapped using remote sensing and GIS. Impact cratering statistics were used to constrain the age of the VRC groups and thermodynamic models of lava–permafrost interactions were used to estimate paleo-ground ice table depth, calculate mobilized (i.e., melted and/or vaporized) water volumes, and infer obliquity-driven climate conditions.

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Explosive lava-water interactions on Earth and Mars

  1. 1. Christopher W. Hamilton [email_address] Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i   Explosive Lava–Water Interactions on Earth and Mars Ph.D. Co-Advisor: Thor Thordarson Co-Authors: Lionel Wilson Ciarán Beggan Ph.D. Advisor: Sarah Fagents Acknowledgements National Aeronautics and Space Administration Icelandic Centre for Research National Science Foundation Geological Society of America Hawai ‘i Geographic Information Coordinating Council University of Hawai ‘i Graduate Student Organization
  2. 2. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions <ul><li>3. Thermodynamic modeling </li></ul>1. Geological mapping and geomorphology 2. Statistical nearest neighbor (NN) analysis Explosive Lava–Water Interactions
  3. 3. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Explosive Lava–Water Interactions Earth: Hamilton CW , T Thordarson, and SA Fagents (2010a) Explosive lava-water interactions I: architecture and emplacement chronology of volcanic rootless cone groups in the 1783- 1784 Laki lava flow.  Bulletin of Volcanology , 10.1007/s00445-009-0330-6. Hamilton CW , SA Fagents, and T Thordarson (2010b) Explosive lava-water interaction II: Self-organization processes among volcanic rootless eruption sites in the 1783-1784 Laki lava flow, Iceland.  Bulletin of Volcanology , 10.1007/s00445-009-0331-5.   Mars: Hamilton CW , SA Fagents, and L Wilson (2010c) Explosive lava-water interactions in Elysium Planitia, Mars: constraints on the formation of the Tartarus Colles cone groups.  Journal of Geophysical Research , (in press). Hamilton CW , SA Fagents, and T Thordarson (2010d) Lava-ground ice interactions in Elysium Planitia, Mars: geomorphological and geospatial analysis of the western Tartarus Colles cone groups.  Journal of Geophysical Research , (in review).
  4. 4. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions   Introduction
  5. 5. Lake Mývatn, Iceland Volcano–H 2 O Interactions Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Volcanic Rootless Cones (VRCs)
  6. 6. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Skaftá River, Iceland Volcanic Rootless Cones (VRCs)
  7. 7. VRC group in the Laki lava flow, Iceland Introduction Methods Results Discussion Conclusions Volcanic Rootless Cones (VRCs) Introduction Earth Mars Discussion Conclusions
  8. 8. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions <ul><ul><li>100 m </li></ul></ul>VRC group in the Laki lava flow, Iceland Volcanic Rootless Cones (VRCs)
  9. 9. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  10. 10. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  11. 11. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  12. 12. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  13. 13. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  14. 14. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  15. 15. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  16. 16. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  17. 17. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  18. 18. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  19. 19. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  20. 20. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  21. 21. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  22. 22. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  23. 23. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  24. 24. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  25. 25. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  26. 26. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  27. 27. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  28. 28. Conceptual Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  29. 29. Neural Networks VRC cross-section within Rauðhólar, Iceland Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Volcanic Rootless Cones (VRCs)
  30. 30. Neural Networks VRC cross-section within Rauðhólar, Iceland Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Volcanic Rootless Cones (VRCs)
  31. 31. Neural Networks VRC cross-section within Rauðhólar, Iceland Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Volcanic Rootless Cones (VRCs)
  32. 32. Neural Networks VRC cross-section within Rauðhólar, Iceland Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Volcanic Rootless Cones (VRCs)
  33. 33. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Volcanic Rootless Cones (VRCs)
  34. 34. 1 km Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions VRC analogs among the western Tartarus Colles cone groups, Mars Volcanic Rootless Cones (VRCs)
  35. 35. 1 km Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Volcanic Rootless Cones (VRCs) VRC analogs among the eastern Tartarus Colles cone groups, Mars
  36. 36. Mars Exploration Rover Spirit images of volcanic rocks in Gusev Crater, Mars Volcano–H 2 O Interactions on Mars Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  37. 37. Mars Exploration Rover Spirit images of volcanic rocks in Gusev Crater, Mars Volcano–H 2 O Interactions on Mars Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  38. 38. Mars Exploration Rover Spirit images of volcanic rocks in Gusev Crater, Mars Volcano–H 2 O Interactions on Mars Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  39. 39. Volcanic Rootless Cones (VRCs) Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions <ul><ul><li>Mars Exploration Program Goals: </li></ul></ul><ul><ul><ul><li>Determine if life ever arose on Mars </li></ul></ul></ul><ul><ul><ul><li>Climate processes and history </li></ul></ul></ul><ul><ul><ul><li>Evolution of the surface and interior </li></ul></ul></ul><ul><ul><ul><li>Prepare for human exploration </li></ul></ul></ul><ul><ul><ul><li>Fossil hydrothermal systems </li></ul></ul></ul><ul><ul><ul><li>Obliquity-driven ground ice stability </li></ul></ul></ul><ul><ul><ul><li>Volcanic and magmatic processes </li></ul></ul></ul><ul><ul><ul><li>Identification of water resources </li></ul></ul></ul>
  40. 40. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions   Earth
  41. 41. Terrestrial Analog: Laki, Iceland Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions N
  42. 42. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions N Terrestrial Analog: Laki, Iceland
  43. 43. 1070ºC 564 570 568 566 Elevation (m) Rootless Cone Archetypes Brittle Crust Viscous Layer Molten Core Saturated Unsaturated Lava Flow Sediments 800ºC Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  44. 44. 564 570 568 566 Elevation (m) Rootless Cone Archetypes Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  45. 45. 564 570 568 566 Elevation (m) Rootless Cone Archetypes Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  46. 46. 564 570 568 566 Elevation (m) Rootless Cone Archetypes Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  47. 47. 564 570 568 566 Elevation (m) Rootless Cone Archetypes Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  48. 48. 564 570 568 566 Elevation (m) Rootless Cone Archetypes Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  49. 49. 564 570 568 566 Elevation (m) Geospatial Analysis Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  50. 50. 564 570 568 566 Elevation (m) Geospatial Analysis Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  51. 51. 564 570 568 566 Elevation (m) Geospatial Analysis Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Hekla 1104 pumice layer 150 m
  52. 52. 564 570 568 566 Elevation (m) Geospatial Analysis Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions 150 m
  53. 53. Kipuka Mantled Terrain Lava Rootless Cone Crater Crater Floor Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis 1000 m
  54. 54. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis
  55. 55. ○ R a : mean actual distance between Nearest Neighbor (NN) pairs R e : mean expected distance between NNs Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis if R < 1 then clustered if R ≈ 1 then random if R > 1 then repelled
  56. 56. R : 1.00 | c |: 0.05 R : 1.91 | c |: 6.64 R : 0.47 | c |: 7.13 Clustered Poisson (Random) Evenly Spaced x R < 1 R = 1 R > 1 Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis Figure adapted from Bruno et al. (2006)
  57. 57. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis
  58. 58. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis Population size (N) Repelled Clustered
  59. 59. Discharge from extraction well Maximum radius of influence Distance from extraction well Aquifer thickness Water saturated depth at r Water table draw down at r Q R r H h S Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis
  60. 60. Discharge from extraction well Maximum radius of influence Distance from extraction well Aquifer thickness Water saturated depth at r Water table draw down at r Q R r H h S Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis
  61. 61. Discharge from extraction well Maximum radius of influence Distance from extraction well Aquifer thickness Water saturated depth at r Water table draw down at r Q R r H h S Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Geospatial Analysis
  62. 62. <ul><li>3. Sample-size-dependent organization </li></ul>1. Lava pathways effect VRC morphology 2. VRC groups are diachronous constructs Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Summary
  63. 63. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions   Mars
  64. 64. Tartarus Colles Cone Groups, Mars MOLA Digital Terrain Model of Elysium Planitia, Mars 1000 km 9 km -9 km 0 km Elevation Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  65. 65. 9 km -9 km 0 km Elevation 1000 km Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Tartarus Colles Cone Groups, Mars
  66. 66. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Tartarus Colles Cone Groups, Mars Cerberus Fossae 3 unit Late Amazonian Cerberus Fossae 2 unit Late to Middle Amazonian Elysium Rise unit Early Amazonian to Early Hesperian Crater unit Late Amazonian to Early Hesperian Arcadia Planitia unit Late to Early Hesperian Nepenthes Mensae unit Early Hesperian to Early Noachian Noachian Hesperian Amazonian 3.5 1.8 0 Billions of years before present
  67. 67. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Tartarus Colles Cone Groups, Mars Elysium Rise unit Early Amazonian to Early Hesperian Nepenthes Mensae unit Early Hesperian to Early Noachian VRC-hosting Tartarus Colles lava Shield-like Tartarus Colles lava Elevation (m) Noachian Hesperian Amazonian 3.5 1.8 0 Billions of years before present
  68. 68. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Tartarus Colles Cone Groups, Mars Elysium Rise unit Early Amazonian to Early Hesperian Nepenthes Mensae unit Early Hesperian to Early Noachian VRC-hosting Tartarus Colles lava Shield-like Tartarus Colles lava VRCs Elevation (m) Noachian Hesperian Amazonian 3.5 1.8 0 Billions of years before present
  69. 69. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Tartarus Colles Cone Groups, Mars Elysium Rise unit Early Amazonian to Early Hesperian Nepenthes Mensae unit Early Hesperian to Early Noachian VRC-hosting Tartarus Colles lava Shield-like Tartarus Colles lava VRCs Elevation (m) Noachian Hesperian Amazonian 3.5 1.8 0 Billions of years before present
  70. 70. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Tartarus Colles Cone Groups, Mars Elysium Rise unit Early Amazonian to Early Hesperian Nepenthes Mensae unit Early Hesperian to Early Noachian VRC-hosting Tartarus Colles lava Shield-like Tartarus Colles lava VRCs Elevation (m) Pitted terrain Noachian Hesperian Amazonian 3.5 1.8 0 Billions of years before present
  71. 71. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Tartarus Colles Cone Groups, Mars Elysium Rise unit Early Amazonian to Early Hesperian VRC-hosting Tartarus Colles lava Late to Middle Amazonian (75–250 Ma)
  72. 72. (log N i ) Nearest Neighbor (NN) Results Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Repelled Clustered
  73. 73. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Nearest Neighbor (NN) Results Repelled Clustered
  74. 74. Nearest Neighbor (NN) Results Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Repelled Clustered
  75. 75. (log N i ) Nearest Neighbor (NN) Results Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Repelled Clustered
  76. 76. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Nearest Neighbor (NN) Results Lava Thickness N 10 km
  77. 77. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Nearest Neighbor (NN) Results Lava Thickness N 10 km
  78. 78. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Nearest Neighbor (NN) Results Lava Thickness N 10 km
  79. 79. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Nearest Neighbor (NN) Results 3 km Lava Thickness N 10 km
  80. 80. 3 km 3 km Lava Thickness Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions N 10 km Nearest Neighbor (NN) Results
  81. 81. Thermodynamic Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  82. 82. Thermodynamic Model Differences in isotherm depths on Mars and the Earth Mars (T A = 210 K) Earth (T A = 270 K) Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  83. 83. Thermodynamic Model Hydrothermal system longevity (substrate temperature >273 K) Mars (T A = 210 K) Earth (T A = 270 K) Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  84. 84. Thermodynamic Model X Y X Y Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions X Y
  85. 85. Thermodynamic Model Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions X Y X Y X Y X Y
  86. 86. Thermodynamic Model 273 K at T L = 1273 K Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions X Y X Y X Y X Y
  87. 87. Thermodynamic Model 273 K at T L = 1273 K Maximum 273 K Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions X Y X Y X Y X Y
  88. 88. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions   Discussion
  89. 89. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Summary
  90. 90. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Summary
  91. 91. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Summary
  92. 92. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Summary
  93. 93. Summary Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  94. 94. Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Summary Minimum H 2 O volume = (VRC domain area) × (Isotherm depth at T L = 1273 K) × (Substrate porosity) Minimum H 2 O volume = (2014 km 2 ) x (21 to 42 m for 30 to 60 m-thick lava) × (0.1 to 0.3) Minimum H 2 O volume = ~3.7 to 22.5 km 3
  95. 95. Summary Minimum H 2 O volume = (VRC domain area) × (Isotherm depth at T L = 1273 K) × (Substrate porosity) Minimum H 2 O volume = (2014 km 2 ) x (21 to 42 m for 30 to 60 m-thick lava) × (0.1 to 0.3) Minimum H 2 O volume = ~3.7 to 22.5 km 3 Paleo-climate = intermediate obliquity (~35°) 75–250 Ma ago, with excursions to ~25–32° Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  96. 96. Summary Minimum H 2 O volume = (VRC domain area) × (Isotherm depth at T L = 1273 K) × (Substrate porosity) Minimum H 2 O volume = (2014 km 2 ) x (21 to 42 m for 30 to 60 m-thick lava) × (0.1 to 0.3) Minimum H 2 O volume = ~3.7 to 22.5 km 3 Paleo-climate = intermediate obliquity (~35°) 75–250 Ma ago, with excursions to ~25–32° Hydrothermal system longevity = up to ~1300 years for 75 m-thick lava and T A = 210 K Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  97. 97.   Conclusions Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  98. 98. Conclusions Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Local Global <ul><li>How do volcanic </li></ul><ul><li>rootless constructs </li></ul><ul><li>(VRCs) form? </li></ul>VRCs form due to explosive lava–water interactions that indicate at random in favorable environments VRC groups are diachronous structures with VRC morphologies recording stages of lava emplacement Thermokarst can form in association with VRCs if extended ground ice melting causes lava foundering
  99. 99. Conclusions Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions Local Global <ul><li>How do volcanic </li></ul><ul><li>rootless constructs </li></ul><ul><li>(VRCs) form? </li></ul><ul><li>Can rootless cones be identified using geospatial analysis? </li></ul>VRCs form due to explosive lava–water interactions that indicate at random in favorable environments VRC groups are diachronous structures with VRC morphologies recording stages of lava emplacement Thermokarst can form in association with VRCs if extended ground ice melting causes lava foundering Rootless eruption sites exhibit scale-dependent variations in nearest neighbor statistics, but cannot be distinguished using one geospatial parameter
  100. 100. VRCs form due to explosive lava–water interactions that indicate at random in favorable environments VRC groups are diachronous structures with VRC morphologies recording stages of lava emplacement Thermokarst can form in association with VRCs if extended ground ice melting causes lava foundering Rootless eruption sites exhibit scale-dependent variations in nearest neighbor statistics, but cannot be distinguished using one geospatial parameter During VRC formation, the western Tartaus Colles region contained >4–22 km 3 H 2 O, and could have had active hydrothermal systems for up to ~1300 years This major volcanic event occurred on Mars ~125 Ma ago, under intermediate (~35°) obliquity conditions supporting a mid-latitude ice table at <21–42 m depth Conclusions <ul><li>How do volcanic </li></ul><ul><li>rootless constructs </li></ul><ul><li>(VRCs) form? </li></ul>Local Global <ul><li>Can rootless cones be identified using geospatial analysis? </li></ul>3. What information do rootless cones provide about the geological evolution of Mars? Introduction Methods Results Discussion Conclusions Introduction Earth Mars Discussion Conclusions
  101. 101.   DGPS Mapping Introduction Methods Results Discussion Conclusions
  102. 102. Terrestrial Analogue: Laki, Iceland Introduction Methods Results Discussion Conclusions N
  103. 103. Terrestrial Analogue: Laki, Iceland Introduction Methods Results Discussion Conclusions
  104. 104. Kipuka Mantled Terrain Lava Rootless Cone Crater Crater Floor Facies Mapping Introduction Methods Results Discussion Conclusions 1000 m
  105. 105. Introduction Methods Results Discussion Conclusions Facies Mapping Differential GPS tracks define facies boundaries 15 m
  106. 106. Introduction Methods Results Discussion Conclusions Facies Mapping DGPS boundaries were digitized in ArcGIS 15 m
  107. 107. Introduction Methods Results Discussion Conclusions Facies Mapping DGPS boundaries were digitized in ArcGIS 15 m
  108. 108. 2216 rootless eruptions sites defined using Differential GPS 86 stratigraphic sections used to constrain kipuka locations and emplacement chronology On Wednesday, August 20, 2008 this geological map was used to prevent renewed quarrying of the Laki rootless cones Introduction Methods Results Discussion Conclusions Facies Mapping
  109. 109. 0.5 m 1.0 m Katla 1918 Laki (S2) Emplacement Chronology Laki S1a Layer (Fissures 1) June 8, 1783 Laki S1b Layer (Fissures 2) June 10-11, 1783 Laki S2 Layer (Fissure 3) June 14, 1783 Introduction Methods Results Discussion Conclusions
  110. 110. 0.5 m Katla 1918 Laki (S2) Emplacement Chronology 1.0 m Laki S1a Layer (Fissures 1) June 8, 1783 Laki S1b Layer (Fissures 2) June 10-11, 1783 Laki S2 Layer (Fissure 3) June 14, 1783 Introduction Methods Results Discussion Conclusions
  111. 111. 0.5 m Katla 1918 Laki (S1 + S2) Katla 1755 Katla 1625 Emplacement Chronology 1.0 m Laki S1a Layer (Fissures 1) June 8, 1783 Laki S1b Layer (Fissures 2) June 10-11, 1783 Laki S2 Layer (Fissure 3) June 14, 1783 Introduction Methods Results Discussion Conclusions
  112. 112. Emplacement Chronology Introduction Methods Results Discussion Conclusions
  113. 113.   Nearest Neighbor (NN) Analysis Introduction Methods Results Discussion Conclusions
  114. 114. ○ R a : mean actual distance between Nearest Neighbor (NN) pairs R e : mean expected distance between NNs c: test statistic for measuring the significance of R σ : standard error of the mean expected NN distance R e Introduction Methods Results Discussion Conclusions Geospatial Analysis
  115. 115. Introduction Methods Results Discussion Conclusions Geospatial Analysis Population size (N)
  116. 116. Introduction Methods Results Discussion Conclusions Geospatial Analysis Population size (N)
  117. 117.   Thermodynamic Modeling Introduction Methods Results Discussion Conclusions
  118. 118. Thermodynamic Model T = temperature at time t in seconds T L = temperature of the lava (initially equal to T M ) T B = temperature at the base of the flow (initially equal to T M ) T M = temperature of basaltic magma (1450 or 1617 K) d = depth beneath the top of the flow in meters k = thermal diffusivity (7 × 10 -7 m 2 s -1 ) Other boundary conditions and considerations: 1. Upper flow surface of the lava is kept at ambient temperature ( T A ) 2. Substrate temperature is initially set to T A 3. k adjusted to account for the heat absorbed in melting and vaporizing H 2 O Analytical model: Introduction Methods Results Discussion Conclusions
  119. 119. Thermodynamic Model Introduction Methods Results Discussion Conclusions Effects of ambient temperature (T A ) on isotherm depth Mars (T A = 210 K) Earth (T A = 270 K)
  120. 120. Thermodynamic Model Introduction Methods Results Discussion Conclusions
  121. 121.   Obliquity-Driven Climate Change Introduction Methods Results Discussion Conclusions
  122. 122. Obliquity-Driven Climate Change Introduction Methods Results Discussion Conclusions Probabilistic obliquity scenarios for Mars during the past 250 Ma (Laskar et al. , 2004) Obliquity (Axial Tilt) Plane of the ecliptic If ice then obliquity >25° If desiccation then obliquity <32°

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