Influence of ice degradation on planetary landscapes
The present thesis aims at getting new understandings on how ground water ice and periglacial processes influence surface geomorphology on Earth and on Mars. I am hence investigating two periglacial landforms: molards and thermal-contraction polygons. On Earth, molards are cones of loose debris foun...
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| Other Authors: | , , , , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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HAL CCSD
2023
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| Online Access: | https://theses.hal.science/tel-04629918 https://theses.hal.science/tel-04629918/document https://theses.hal.science/tel-04629918/file/PHILIPPE.pdf |
| Summary: | The present thesis aims at getting new understandings on how ground water ice and periglacial processes influence surface geomorphology on Earth and on Mars. I am hence investigating two periglacial landforms: molards and thermal-contraction polygons. On Earth, molards are cones of loose debris found in landslide deposits. It was recently attested that they are former ice-cemented blocks of sediment, that were transported by a landslide and progressively degraded within its deposits into conical shapes. They could represent accurate spatial and temporal markers of the degradation of mountain permafrost. Therefore, I provide here a systematic way to study molards, based on analogue modelling experiments monitored by an automated time-lapse photogrammetry system I developed. I also present a study on the firstly-identified potential martian molards, that provide insights into the geological setting of the ejecta from the Hale crater. Terrestrial thermal-contraction polygons are known to result from the thermal contraction of ground ice, which forms surficial networks of polygonal fractures. Water or lithic material can infill those fractures, and with repeated freeze-thaw cycles of water generate polygons with various morphologies. On Mars, polygons of similar dimensions and showing similar morphologies are observed. Therefore, I present here a study that investigates martian thermal-contraction polygons in Utopia Planitia, concluding on the geologically recent activity of liquid water in the area. I also present a study that investigates thermal-contraction polygons located on geomorphological units in Utopia Planitia, providing insights into both the timing of formation of thermal-contraction polygons and the geological history of the area. Cette thèse présente de nouvelles connaissances sur le lien entre glace du sol et géomorphologie, dans des contextes terrestres et martiens. J’étudie deux morphologies : les molards et les polygones de contraction thermique. Sur Terre, les molards sont des cônes de débris ... |
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