The formation mechanism of long run-out landslides on planetary bodies

Lead Research Organisation: University College London
Department Name: Earth Sciences

Abstract

Landslides are not only an important landscape-forming process on solid bodies throughout the Solar System, but on Earth also represent a natural hazard to life and infrastructure. The mechanisms responsible for the onset and flow of long run-out (typically tens of km) landslides are particularly poorly understood. Numerous methods have been proposed to explain long run-out landslide formation, including, but not limited to: basal fine powders, interstitial fluids, pore fluid pressure, air pockets, steam generation and thermal pressurisation, frictional melts, lubrication, fluidization and dynamic fragmentation.

On Earth, fieldwork allows the in situ investigation of long run-out landslide deposits, which can reveal important insights into the formation mechanism. The slipping zone, or basal plane, of large landslides that accommodates much of the slip displacement is, in many cases, saturated with fluid. The amount of pore fluid pressure can lower the apparent friction of the sliding mass by carrying some of the overburden and reducing the effective stress. Frictional heating and chemical reactions of materials in the landslide slip zone can also lead to pressurization of the pore fluid along the shear zone and reduce the frictional resistance to sliding, by decomposing or dehydrating slip zone material and produce overpressured fluids. This chemical-thermal-poro-mechanical process can lead to extremely high sliding velocity (10-100 m/sec) and can explain the anomalously large runouts. For example, recent studies showed that at the Heart Mountain landslide, the largest sub-aerial landslide on Earth, shear heating at high slip velocities could have caused thermal decomposition and the release of carbon dioxide, which allowed catastrophic slip even on a low angle detachment surface. However, investigating these deposits in the rock record on Earth can be hampered by active geological processes driven by plate tectonics. Therefore it is useful to use other planetary bodies, where deposits have been better preserved due to lower rates of geological activity.

On Mars, there are a large number of long run-out landslides that suffer from a similar uncertainty in formation mechanism , but which are also important in dating key geological processes. Some studies have proposed dehydration controls on the initiation and mechanics of enormous Martian landslides. The scale of such landslides can be seen in Valles Marineris, Mars. On the Moon, a long run-out landslide, thought to be triggered by ejecta from the distant Tycho impact event, has been used as a key calibration point in age dating planetary surfaces through crater size-frequency analysis. This project will address the question of how long run-out landslides initiate and propagate on Earth, the Moon and Mars. This will involve a combination of in situ analysis for terrestrial deposits, and the latest high-resolution remote sensing data (e.g. LROC, HiRISE) for the Moon and Mars, as well as developing. Co-supervisor Schmitt also carried out fieldwork at one of the study landslides in the Taurus-Littrow valley on the Moon during the Apollo 17 mission.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/N504476/1 01/10/2015 31/03/2021
1631702 Studentship ST/N504476/1 01/02/2017 31/07/2020 Giulia Magnarini
 
Title Mega Landslides Collection 
Description Here is a collection of images of long runout landslides on Mars. Some are oblique views made using ArcScene and DEMs and orthophotos made using SocetSet photogrammetry software. Dataset is CTX imagery. CTX is a camera on board the Mars Reconnaissance Orbiter with 6 m/px resolution. 
Type Of Art Image 
Year Produced 2019 
Impact These images are free for downloading and can be used by anyone for non-commercial purposes. 
URL https://rdr.ucl.ac.uk/articles/Mega_Landslides_Collection/9778016
 
Title CTX Digital Elevation Models - Coprates Labes long runout landslide, Mars 
Description CTX and HiRISE images, and CTX Stereo-Derived Digital Elevation Models (DEMs) of the Coprates Labes long runout landslide in Valles Marineris, Mars. Dataset in the paper: Longitudinal ridges imparted by high-speed granular flow mechanisms in martian landslides by Magnarini, G., Mitchell T.M., Grindrod P.M., Goren L. and Schmitt H.H. (2019). Nature Communications 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Impact Allow the transparency of the data used for the published work and allow the reproducibility of our analysis. 
URL https://rdr.ucl.ac.uk/articles/CTX_Digital_Elevation_Models_-_Coprates_Labes_long_runout_landslide_M...
 
Description Blog post for the Geomorphology Image of the Month: 3D reconstruction of long runout landslides on Mars 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Blog post describing the method I use to study long runout landslide on Mars and providing view of the surface of Mars, which the readers have found incredible.
Year(s) Of Engagement Activity 2019
URL https://planetarygeomorphology.wordpress.com/2019/06/01/3d-reconstruction-on-long-runout-landslides-...
 
Description Pitch for The Conversation : Mars: we may have solved the mystery of how its landslides form 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Pitch for the online magazine The Conversation.

The Conversation is an independent source of news and views, sourced from the academic and research community and delivered direct to the public.

Our article reached 24,552 readers, with 43 retweets of the article.
Year(s) Of Engagement Activity 2019
URL https://theconversation.com/mars-we-may-have-solved-the-mystery-of-how-its-landslides-form-127645
 
Description Press Release: Martian landslides not conclusive evidence of ice 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Press release of our new publication in Nature Communication
Year(s) Of Engagement Activity 2019
URL https://www.ucl.ac.uk/news/2019/oct/martian-landslides-not-conclusive-evidence-ice