{"id":8302,"date":"2014-03-13T09:11:05","date_gmt":"2014-03-13T09:11:05","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=8302"},"modified":"2014-03-13T09:11:05","modified_gmt":"2014-03-13T09:11:05","slug":"mount-la-perouse-landslide-images","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2014\/03\/13\/mount-la-perouse-landslide-images\/","title":{"rendered":"The Mount La Perouse landslide: new images"},"content":{"rendered":"
The Mount La Perouse landslide: a Pleaides image<\/h5>\n

Last week Marten Geertsema<\/a> flew up to the Mount La Perouse landslide in Alaska<\/a>.\u00a0 He has very kindly made a set of images that he took from the air and on the ground available. Marten and Colin Stark<\/a> also arranged the acquisition of a Pleaides high resolution satellite image.\u00a0 Colin has kindly generated this image of the landslide, which gives a fantastic overview of the slide:<\/p>\n

\"Mount<\/a>

Pleaides image courtesy of Colin Stark<\/p><\/div>\n

..<\/p>\n

The source area of the Mount La Perouse landslide<\/h5>\n

This image shows the source area of the Mount La Perouse landslide.\u00a0 Note the structure in the rocks behind the failure scar.\u00a0 The general geological structure here is an anticline, the core of which has been eroded out by the glacier to form the valley.\u00a0 Thus, the basal shear surface of the landslide is the natural structure in the rocks, with the form of the anticline allowing the plane of weakness to daylight.\u00a0 The rear scar appears to have been defined by a sub-vertical joint.\u00a0 Thus, the landslide itself is a giant wedge; it is perhaps inevitable that this slope was showing some signs of distress prior to failure:<\/p>\n

\"Mount<\/a>

Image courtesy of Marten Geertsema<\/p><\/div>\n

..<\/p>\n

The material that formed the Mount La Perouse landslide<\/h5>\n

The rock material that formed the initial failure of the landslide was gabbro according to the geological maps (hat-tip to Colin for digging that information out).\u00a0 However, upon impact at the foot of the slope this is likely to have shattered and then to have entrained snow and ice.\u00a0 The resulting deposit at the foot of the slide is thus a complex mixture, which appears to consist of a matrix of dirty ice (possibly slush during the movement?) with clasts of intact ice and gabbro (note the handle of an ice axe for scale):<\/p>\n

\"Mount<\/a>

Image courtesy of Marten Geertsema<\/p><\/div>\n

..<\/p>\n

The Mount La Perouse landslide track<\/h5>\n

An interesting aspect of the Mount La Perouse landslide is its behaviour upon impacting the valley floor.\u00a0 The satellite images show considerable super-elevation – i.e. it ran up the far side of the valley before turning to flow downhill.\u00a0 This image shows the run up on the opposite valley side:<\/p>\n

\"Mount<\/a>

Image courtesy of Marten Geertsema<\/p><\/div>\n

..<\/p>\n

The slide then travelled down the valley, but with a rather complex flow pattern en route:<\/p>\n

\"Mount<\/a>

Image courtesy of Marten Geerstema<\/p><\/div>\n

..<\/p>\n

There is a great deal of work to do to understand this landslide properly, and it does deserve a detailed investigation.\u00a0 Unfortunately, snowfall is likely to mean that it will soon be difficult to work on it.<\/p>\n","protected":false},"excerpt":{"rendered":"

Marten Geertsema has kindly made a set of images of the Mount La Perouse landslide available. These were collected during a field visit last week.<\/p>\n","protected":false},"author":22,"featured_media":8308,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[340,469,959,775,306,48],"class_list":["post-8302","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-alaska","tag-featured","tag-landslide-report","tag-mount-la-perouse","tag-rock-avalanche","tag-usa"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/8302","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=8302"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/8302\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/8308"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=8302"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=8302"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=8302"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}