{"id":30937,"date":"2019-05-09T07:17:19","date_gmt":"2019-05-09T07:17:19","guid":{"rendered":"https:\/\/blogs.agu.org\/landslideblog\/?p=30937"},"modified":"2019-05-09T07:17:19","modified_gmt":"2019-05-09T07:17:19","slug":"rock-avalanche-mobility","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2019\/05\/09\/rock-avalanche-mobility\/","title":{"rendered":"Rock avalanche mobility is controlled by the characteristics of material in the path of the flow"},"content":{"rendered":"<h4>Rock avalanche mobility is controlled by the characteristics of material in the path of the flow<\/h4>\n<p><a href=\"https:\/\/blogs.agu.org\/landslideblog\/2017\/09\/12\/rock-avalanche-alaska\/\">Rock avalanche mobility<\/a> is one of the most intriguing aspects of landslide behaviour.\u00a0 It has long been recognised that this type of landslide tends to travel <a href=\"https:\/\/blogs.agu.org\/landslideblog\/2014\/07\/08\/komansu-rock-avalanche-1\/\">faster and further<\/a> than would be expected from simple friction parameters.\u00a0 There has been a huge amount of debate as to the causes of this behaviour, with multiple theories having been proposed, some of which have been quite exotic.\u00a0 To date no consensus position has emerged, and the debate rages on.<\/p>\n<p>In a new contribution to the discussion on rock avalanche mobility, a paper in the journal <a href=\"https:\/\/www.sciencedirect.com\/science\/journal\/00137952\"><em>Engineering Geology<\/em><\/a> (<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0013795218319240\">Aaron and McDougall 2019<\/a>) examines 45 well constrained rock avalanche case histories to better understand the controls on their runout.\u00a0 Their work used a semi-empirical modelling approach to back analyse the mobility of the landslides, testing a series of hypotheses centred on the idea that rock avalnche mobility is controlled, at least in part, by interaction with the basal materials that they encounter along their path.\u00a0 This is perhaps most easily imagined in the context of flowing over glacial ice, such as in <a href=\"https:\/\/blogs.agu.org\/landslideblog\/2016\/07\/03\/lamplugh-glacier-rock-avalanche-1\/\">this beautiful example<\/a>:<\/p>\n<div id=\"attachment_19134\" style=\"width: 650px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-19134\" class=\"size-full wp-image-19134\" src=\"https:\/\/blogs.agu.org\/landslideblog\/files\/2016\/07\/16_07-Alaska-1a-e1467532157303.jpg\" alt=\"Lamplugh Glacier\" width=\"640\" height=\"427\" \/><p id=\"caption-attachment-19134\" class=\"wp-caption-text\">The <a href=\"https:\/\/blogs.agu.org\/landslideblog\/2016\/07\/03\/lamplugh-glacier-rock-avalanche-1\/\">Lamplugh Glacier rock avalanche<\/a> via Paul Swanstrom.<\/p><\/div>\n<p>In this case, flowing over a very low friction ice surface might be expected to increase rock avalanche mobility.\u00a0 The same might also occur where the landslide encounters loose, saturated materials, but perhaps to a lesser degree.<\/p>\n<p>The authors conclude that for many of these landslides their behaviour can be best modeled by assuming that the frictional rheology \/ resistance of the landslide changes in the transition from the source zone to the runout path. In general where the rock avalanche ran across bedrock, the resistance to motion was found to be high, but where the path traversed ice or a saturated substrate the resistance to motion was found to be much lower.<\/p>\n<p>The results are a really interesting contribution to the debate. This matters as high mobility rock avalanches can have a devastating impact on communities and infrastructure, and unsurprisingly there is increasing interest in trying to forecast likely behaviour.\u00a0 As the authors state:<\/p>\n<p><em>&#8220;&#8230;forecasts must parameterize the relationship that governs the basal resistance the rock avalanche experiences during emplacement&#8230;<a class=\"workspace-trigger\" href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0013795218319240#f0035\" name=\"bf0035\"><\/a>this choice must account for the expected shear characteristics of the path material&#8221;<\/em><\/p>\n<h4>Reference<\/h4>\n<p>Aaron, J. and McDougall, S. 2019.\u00a0 <a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0013795218319240\">Rock avalanche mobility, the role of path material<\/a>. <em>Engineering Geology<\/em>. <a href=\"https:\/\/doi.org\/10.1016\/j.enggeo.2019.05.003\">https:\/\/doi.org\/10.1016\/j.enggeo.2019.05.003<\/a><\/p>\n<!-- AddThis Advanced Settings generic via filter on the_content --><!-- AddThis Share Buttons generic via filter on the_content -->","protected":false},"excerpt":{"rendered":"<p>A new study in the journal Engineering Geology indicates that a key control on rock avalanche mobility is the characteristics of the material along the path <!-- AddThis Advanced Settings generic via filter on wp_trim_excerpt --><!-- AddThis Share Buttons generic via filter on wp_trim_excerpt --><\/p>\n","protected":false},"author":22,"featured_media":19134,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[544],"tags":[469,952,17,306,369],"class_list":["post-30937","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-review-of-a-paper","tag-featured","tag-mobility","tag-research","tag-rock-avalanche","tag-runout"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/30937","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/comments?post=30937"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/30937\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/19134"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=30937"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=30937"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=30937"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}