{"id":249,"date":"2011-05-27T17:16:48","date_gmt":"2011-05-27T16:16:48","guid":{"rendered":"http:\/\/all-geo.org\/volcan01010\/?p=249"},"modified":"2011-06-01T19:03:43","modified_gmt":"2011-06-01T18:03:43","slug":"grimsvotn-images-of-uk-ashfall","status":"publish","type":"post","link":"https:\/\/all-geo.org\/volcan01010\/2011\/05\/grimsvotn-images-of-uk-ashfall\/","title":{"rendered":"Gr\u00edmsv\u00f6tn: images of UK ashfall"},"content":{"rendered":"<p>In the previous post, I highlighted some <a href=\"http:\/\/all-geo.org\/volcan01010\/2011\/05\/grimsvotn-uk-ashfall\/\">indirect measurements of Gr\u00edmsv\u00f6tn ash<\/a> in the UK.\u00a0 Now that there has been time to collect and process samples there is lots of concrete, irrefutable proof that the ash cloud came over the UK on Tuesday.\u00a0 I really despair at the amount of media coverage that was given to the &#8216;Ash Cloud Myth&#8217; camp, as it diverted attention from legitimate and important questions such as:<\/p>\n<ul>\n<li>How can we improve the way that we use satellite data and other observations to check and refine model outputs?<\/li>\n<li>How exactly are all the possible effects of ash on an aircraft combined to determine the safe flying threshold?\u00a0 What are the extra risks of setting it at 5 or 25 or even 50 mg m<sup>-3<\/sup>?<\/li>\n<li>How much of the decision to fly should be with the operators, and how much with the government?<\/li>\n<\/ul>\n<p>These questions are far more subtle, and the best answers will take time to find.\u00a0 We have come a lot closer to them in the year since Eyjafjallaj\u00f6kull.\u00a0 Hopefully we will be closer still by the next time.\u00a0 Because <a href=\"http:\/\/all-geo.org\/volcan01010\/2011\/02\/ash-cloud-closes-airports-chances\/\">there will be a next time<\/a>&#8230;<\/p>\n<h3>How many roads must a man walk down before you call him a man?<\/h3>\n<p>Volcanic ash, pollen, soot, mineral dust, insects and bits of leaves.\u00a0 And rain.<\/p>\n<p>Not a very helpful answer, but that is what is actually blowin&#8217; in the wind.\u00a0 Here are a collection of images of ash samples from the UK.\u00a0 They are presented in order of increasing magnification.<\/p>\n<p><em><strong>Reflected light microscope (45x magnification): sticky tape samples<\/strong><\/em><\/p>\n<p>The image shows what I found in my saucepan sample, collected on Wednesday night using the <a href=\"http:\/\/all-geo.org\/volcan01010\/2011\/05\/ash-sampling\/\">method described here<\/a>.\u00a0 Unfortunately, it doesn&#8217;t have any obvious ash in it.\u00a0 Most of the ash fell on Tuesday, so I missed it here.\u00a0 Some of the ash sightings during the Eyjafjallaj\u00f6kull eruption turned out to be false alarms, so I&#8217;ve put up this picture to show the kinds of things that are blowing around all the time.<\/p>\n<div id=\"attachment_252\" style=\"width: 610px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-252\" class=\"size-full wp-image-252\" src=\"http:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rainwater_contents.jpg\" alt=\"Mineral grains in the rainwater\" width=\"600\" height=\"450\" srcset=\"https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rainwater_contents.jpg 600w, https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rainwater_contents-300x225.jpg 300w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><p id=\"caption-attachment-252\" class=\"wp-caption-text\">Assorted mineral grains collected from rainwater in Edinburgh.  Most of these are &gt;100 microns in diameter.  So far, ash grains from the UK have been less than 50 microns.  Other samples contained soot, insects and bits of plant material.<\/p><\/div>\n<p>The British Geological Survey made a <a href=\"http:\/\/\">request for samples<\/a> from the public, and these are beginning to arrive now.\u00a0 Hopefully they will have more luck than I did.<\/p>\n<p><em><strong>Transmitted light microscope (500x magnification): pollen sampling slides<\/strong><\/em><\/p>\n<p>The Met Office measure the amount of pollen in the air each day, in order to make <a href=\"http:\/\/www.metoffice.gov.uk\/health\/public\/pollen-forecast\">pollen forecasts<\/a>.\u00a0 These are useful for hayfever sufferers.\u00a0 This week, the sampling equipment also trapped volcanic ash grains, which are about the same size.\u00a0 The grains in the images below were collected in Lerwick and in Exeter between Monday and Wednesday, demonstrating that although the worst of the ash was in Scotland, there were lower concentrations all over the country.<\/p>\n<p>The first image shows an individual ash grain that fell in <span style=\"text-decoration: line-through\">Exeter on Monday night<\/span> in Lerwick on Tuesday or Wednesday.\u00a0 The bigger grain is about 50 microns in diameter (i.e. you could fit ~20 of them in a millimetre).\u00a0 Magma is a mixture of crystals and bubbles and molten rock.\u00a0 When it freezes quickly during an explosive eruption, the molten rock turns into glass.\u00a0 You can see the glass and bubble shapes clearly in this grain.\u00a0 (Compare it with an Eyjafjallaj\u00f6kull grain shown <a href=\"http:\/\/all-geo.org\/volcan01010\/2011\/05\/grimsvotn-eruption-more-questions-and-answers\/\">in this post<\/a>.)<\/p>\n<div id=\"attachment_257\" style=\"width: 610px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-257\" class=\"size-full wp-image-257\" src=\"http:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/lerwick_grains.jpg\" alt=\"Ash grains from Lerwick\" width=\"600\" height=\"450\" srcset=\"https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/lerwick_grains.jpg 600w, https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/lerwick_grains-300x225.jpg 300w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><p id=\"caption-attachment-257\" class=\"wp-caption-text\">Basaltic ash grains from Lerwick.  The larger grain shows bubble-wall shapes.  The right-hand bubble contains finer ash grains inside it.  Note: the original edit of this post featured a grain from an Exeter pollen slide; this image replaces that one.<\/p><\/div>\n<p>The second image is from Tuesday&#8217;s slide.\u00a0 What looks like leopard-print wall paper is actually a fossilised rain shower.\u00a0 Each of the little circles was an ash-filled raindrop that was collected on the sample slide.\u00a0 Rainfall (or &#8216;wet deposition&#8217;) is an important factor in removing ash from the plume.<\/p>\n<div id=\"attachment_250\" style=\"width: 610px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-250\" class=\"size-full wp-image-250\" src=\"http:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rain_drops.jpg\" alt=\"Exeter pollen sample slide\" width=\"600\" height=\"450\" srcset=\"https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rain_drops.jpg 600w, https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rain_drops-300x225.jpg 300w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><p id=\"caption-attachment-250\" class=\"wp-caption-text\">A fossilised rain shower.  Drops of ash-laden rain landed on the Met Office pollen sampling slides.<\/p><\/div>\n<p>The third image is a close-up of the fossil raindrops.\u00a0 Each one forms a ring about 50 microns wide, and consists of 50-100 grains of ash, each only 5-10 microns in diameter.\u00a0 The clear, round blobs that form lines down the image are bubbles in the glue on the slide.<\/p>\n<p><em><strong> <\/strong><\/em><\/p>\n<div id=\"attachment_251\" style=\"width: 610px\" class=\"wp-caption aligncenter\"><em><strong><em><strong><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-251\" class=\"size-full wp-image-251\" src=\"http:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rain_drops_zoom.jpg\" alt=\"Exeter pollen sample slide zoom\" width=\"600\" height=\"450\" srcset=\"https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rain_drops_zoom.jpg 600w, https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/rain_drops_zoom-300x225.jpg 300w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/strong><\/em><\/strong><\/em><p id=\"caption-attachment-251\" class=\"wp-caption-text\">Close up of the pollen sample slide, showing rings of tiny individual ash grains.<\/p><\/div>\n<p><em><strong>Scanning Electron Microscope (~2000x magnification): rain-washed dust<\/strong><\/em><\/p>\n<p>The ash grains that have reached the UK are generally very small, so a scanning electron microscope is used to get a good look at them, at magnifications of 2000x or sometimes more.\u00a0 A sample of dust from a car parked in Lerwick, in the Shetland islands, was analysed by the <a href=\"http:\/\/www.sepa.org.uk\">Scottish Environmental Protection Agency<\/a>.\u00a0 It was found that the dust contained thousands of tiny (less than 10 microns), ash shards.\u00a0 Many of these had clumped together to form &#8216;aggregates&#8217;.\u00a0 Aggregate formation is another important process in deposition of ash from a plume, because a big clump of many grains will fall to Earth much more quickly than the individual grains would do alone.<\/p>\n<p style=\"text-align: left\">\n<div id=\"attachment_253\" style=\"width: 610px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.sepa.org.uk\/about_us\/news\/other\/grimsvotn_volcanic_eruption.aspx\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-253\" class=\"size-full wp-image-253 \" src=\"http:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/sepa_ash_sem.jpg\" alt=\"SEM image of volcanic ash\" width=\"600\" height=\"449\" srcset=\"https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/sepa_ash_sem.jpg 600w, https:\/\/all-geo.org\/volcan01010\/wp-content\/uploads\/2011\/05\/sepa_ash_sem-300x224.jpg 300w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/a><p id=\"caption-attachment-253\" class=\"wp-caption-text\">SEM image of volcanic ash from the SEPA website.<\/p><\/div>\n<p>The image shows a quartz grain amongst a cluster of tiny ash grains, but you wouldn&#8217;t know it just by looking at it.\u00a0 The composition of the grains is worked out using a technique called Energy Dispersive Spectroscopy.\u00a0 This works by using the electron beam to knock other electrons out of the atoms in the sample.\u00a0 The gap is filled by another electron from within the same atom, and energy is released as an X-ray.\u00a0 The wavelength of the X-ray is specific to the type of atom e.g. iron is different to magnesium is different to lead.\u00a0 By measuring the wavelengths of all the X-rays, you can tell which types of atoms are in your sample.\u00a0 Quartz (chemical formula SiO2) produces big spikes corresponding to silicon and oxygen.\u00a0 Volcanic glass contains a huge range of different elements (silicon, oxygen, aluminium, iron, magnesium, calcium, sodium&#8230;.).\u00a0 This is how they worked out what each grain was.<\/p>\n<p>Have a look at the SEPA website for <a href=\"http:\/\/www.sepa.org.uk\/about_us\/news\/other\/grimsvotn_volcanic_eruption.aspx\">the full report<\/a>, which contains lots of other nice images.\u00a0 The British Geological Survey has SEM images on their <a href=\"http:\/\/www.bgs.ac.uk\/research\/highlights\/icelandGrimsvotn.html?src=sfb\">Gr\u00edmsv\u00f6tn pag<\/a>e, too.<\/p>\n<h6>EDIT 01\/06\/11: Replace image of individual tephra grain with Lerwick example.<\/h6>\n","protected":false},"excerpt":{"rendered":"<p>In the previous post, I highlighted some indirect measurements of Gr\u00edmsv\u00f6tn ash in the UK.\u00a0 Now that there has been time to collect and process samples there is lots of concrete, irrefutable proof that the ash cloud came over the &hellip; <a href=\"https:\/\/all-geo.org\/volcan01010\/2011\/05\/grimsvotn-images-of-uk-ashfall\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-249","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/posts\/249","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/comments?post=249"}],"version-history":[{"count":4,"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/posts\/249\/revisions"}],"predecessor-version":[{"id":256,"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/posts\/249\/revisions\/256"}],"wp:attachment":[{"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/media?parent=249"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/categories?post=249"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/all-geo.org\/volcan01010\/wp-json\/wp\/v2\/tags?post=249"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}