{"id":6141,"date":"2013-03-23T00:01:12","date_gmt":"2013-03-23T00:01:12","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=6141"},"modified":"2013-03-23T07:21:09","modified_gmt":"2013-03-23T07:21:09","slug":"the-role-of-joints-in-controlling-rockfalls","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2013\/03\/23\/the-role-of-joints-in-controlling-rockfalls\/","title":{"rendered":"The role of joints in controlling rockfalls"},"content":{"rendered":"

In Iceland we flew over the spectacular Gullfoss waterfall.\u00a0 This is a wonderful site, although it was pretty cold, as the frozen spray around the waterfall demonstrates:<\/p>\n

\"\"<\/a>.<\/p>\n

Just downstream is an amazing outcrop\u00a0of columnar basalt in the gorge wall .\u00a0 This cannot be easily viewed from the ground (it is on the wrong side), but from the air one gets a pretty good view:<\/p>\n

\"\"<\/a>.<\/p>\n

As well as being a genuinely increadible rock outcrop, this is a very nice illustration of the control that joints play in controlling rockfalls.\u00a0 Let’s zoom into a part of the image above:<\/p>\n

\"\"<\/a>.<\/p>\n

To the right of the columns is a section of heavily-jointed rock.\u00a0 Here (relatively) small pieces can detach – and indeed below this section of cliff there are some blocks sitting on a ledge. The result is a face that is comparatively planar.\u00a0 The columnar basalt.itself yields rockfalls much less easily.\u00a0 To detach, a block needs to topple, or to fracture, both of which are quite hard to achieve.\u00a0 The result is a rockface that, at least along a horizontal line, has a great deal more relief.\u00a0 Below the basalt is an almost unjointed section – this probably erodes primarily through abrasion of debris carried by the river when it is in flood.\u00a0 Leaving a smooth but undulating, surface.<\/p>\n

It is for this reason that we often consider that the discontinuities (joints) are more important than the rock itself when trying to understand potential rockfalls.<\/p>\n","protected":false},"excerpt":{"rendered":"

A post providing a spectaular example of columnar jointing from Iceland, examining the role that joints play in rockfalls<\/p>\n","protected":false},"author":22,"featured_media":6142,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[711,109,710,56],"class_list":["post-6141","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-gorge","tag-iceland","tag-joints","tag-rockfall"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/6141","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=6141"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/6141\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/6142"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=6141"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=6141"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=6141"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}