{"id":6365,"date":"2011-06-23T22:45:14","date_gmt":"2011-06-24T03:45:14","guid":{"rendered":"http:\/\/all-geo.org\/highlyallochthonous\/?p=6365"},"modified":"2011-06-24T11:46:22","modified_gmt":"2011-06-24T16:46:22","slug":"the-far-travelled-ground","status":"publish","type":"post","link":"https:\/\/all-geo.org\/highlyallochthonous\/2011\/06\/the-far-travelled-ground\/","title":{"rendered":"The far-travelled ground"},"content":{"rendered":"<p><span style=\"float: left; padding: 5px;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/all-geo.org\/highlyallochthonous\/wp-content\/uploads\/2010\/07\/chrisicon2.jpg\" width=\"49\" height=\"50\" alt=\"A post by Chris Rowan\"\/><\/span>Be honest: when Evelyn asked the geoblogosphere, <a href=\"http:\/\/georneys.blogspot.com\/2011\/06\/accretionary-wedge-35-whats-your.html\">&#8216;what&#8217;s your favourite geology word?&#8217;<\/a>, you all knew which word I was going to pick, didn&#8217;t you? Allochthonous. Allochthonous, the word that no-one can spell. Allochthonous, the word no-one can <em>pronounce<\/em>, it seems, given that I am asked how you do whenever I meet a reader of this blog. I personally think it trips off the tongue quite nicely. It is also a word with heft: it sounds like it means something, something important, interesting, monumental. And it does. <\/p>\n<p>&#8216;Allochthonous&#8217; is derived from two greek words: <\/p>\n<ul>\n<li>&alpha;&lambda;&lambda;&omicron;&#962; or allos, meaning other, or different;<\/li>\n<li>&kappa;&theta;&omicron;&nu;&omicron;&#962; or kthonos, meaning earth.<\/li>\n<\/ul>\n<p>So, literally, allochthonous means &#8216;different earth&#8217;; or &#8216;stuff that&#8217;s not from around these parts&#8230;&#8217; In tectonics, it is generally used to describe a sequence that has been moved a long distance from its original location by faulting (most usually, thrust faulting). For example, a sequence of sediments which were originally deposited in the deep sea, and have then been thrust over shallow marine or continental deposits of a similar age.<\/p>\n<div id=\"attachment_6370\" style=\"width: 510px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-6370\" src=\"https:\/\/all-geo.org\/highlyallochthonous\/wp-content\/uploads\/2011\/06\/allochthon.png\" alt=\"\" title=\"allochthon\" width=\"500\" height=\"311\" class=\"size-full wp-image-6370\" srcset=\"https:\/\/all-geo.org\/highlyallochthonous\/wp-content\/uploads\/2011\/06\/allochthon.png 500w, https:\/\/all-geo.org\/highlyallochthonous\/wp-content\/uploads\/2011\/06\/allochthon-300x186.png 300w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><p id=\"caption-attachment-6370\" class=\"wp-caption-text\">The formation of an allochthonous sequence by motion along a large thrust fault. The &#039;autochon&#039; is the stuff that stays put, relatively. Colour coding represents continental (red) shallow marine (yellow) and deep marine (green) rocks.<\/p><\/div>\n<p><a href=\"http:\/\/georneys.blogspot.com\/2011\/02\/geology-word-of-week-o-is-for-ophiolite.html\">Ophiolites<\/a> would be another good example: the ocean crust itself thrust up from the depths onto the shore.<\/p>\n<div id=\"attachment_3769\" style=\"width: 610px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3769\" src=\"https:\/\/all-geo.org\/highlyallochthonous\/wp-content\/uploads\/2010\/07\/Oman_ophiolite.jpg\" alt=\"\" title=\"Oman Ophiolite\" width=\"600\" height=\"336\" class=\"size-full wp-image-3769\" srcset=\"https:\/\/all-geo.org\/highlyallochthonous\/wp-content\/uploads\/2010\/07\/Oman_ophiolite.jpg 600w, https:\/\/all-geo.org\/highlyallochthonous\/wp-content\/uploads\/2010\/07\/Oman_ophiolite-300x168.jpg 300w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><p id=\"caption-attachment-3769\" class=\"wp-caption-text\">Part of the lower crustal sequence, Oman ophiolite. Photo taken by C. Rowan, 2010<\/p><\/div>\n<p>In a wonderfully evocative turn of phrase, John Challinor&#8217;s Dictionary of Geology describes an allochthon as &#8216;the far-travelled ground&#8217;, and I think this gets to the heart of why I&#8217;ve always loved the word: it embodies the central idea of plate tectonics, the notion that the earth is continuously being reshaped and transformed by the large-scale movement of bits of crust across the Earth&#8217;s surface. Allochthonous thrust sheet, or nappes? You&#8217;re in a continental collision zone, where the opposite shores of a once large ocean &#8211; and bits of the ocean itself &#8211; are all mashed up against each other. Allochthonous terranes? Basically a larger scale version of the same thing, with island arcs and microcontinents once spread across half the planet getting welded together above a <a href=\"http:\/\/entequilaesverdad.blogspot.com\/2011\/06\/seduction-of-subduction.html\">subduction zone<\/a>. Allochthonous conjures up all of the things that I find most fascinating about geology. Plus, it has lots of syllables, something I also have an unhealthy fascination with&#8230;<\/p>\n<p>As it turns out, the word allochthonous does also pop up in other branches of earth science, most particularly within the watery realms of <a href=\"https:\/\/all-geo.org\/highlyallochthonous\/author\/ajefferson\/\">my co-blogger<\/a>. There, it is used to describe material, particularly organic matter such as leaves, which fall or get washed into a stream or lake from the surrounding land (Anne has now provided <a href=\"https:\/\/all-geo.org\/highlyallochthonous\/2011\/06\/when-a-tree-falls-in-a-stream-theres-always-something-around-to-make-use-of-it\/\">a more detailed explanation<\/a>). I don&#8217;t think Anne thinks it&#8217;s quite as cool a word as I do, but it&#8217;s nice that the name of our blog does have a meaning in both of our areas of research. <\/p>\n","protected":false},"excerpt":{"rendered":"<p>Be honest: when Evelyn asked the geoblogosphere, &#8216;what&#8217;s your favourite geology word?&#8217;, you all knew which word I was going to pick, didn&#8217;t you? Allochthonous. Allochthonous, the word that no-one can spell. Allochthonous, the word no-one can pronounce, it seems, &hellip; <a href=\"https:\/\/all-geo.org\/highlyallochthonous\/2011\/06\/the-far-travelled-ground\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16,4,49,19],"tags":[447,448,449],"class_list":["post-6365","post","type-post","status-publish","format-standard","hentry","category-basics","category-geology","category-hydrology","category-tectonics","tag-accretionary-wedge","tag-terminology","tag-words-of-many-syllables"],"_links":{"self":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/6365","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/comments?post=6365"}],"version-history":[{"count":9,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/6365\/revisions"}],"predecessor-version":[{"id":6405,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/6365\/revisions\/6405"}],"wp:attachment":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/media?parent=6365"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/categories?post=6365"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/tags?post=6365"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}