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<title>Subduction – JOIDES Resolution</title>
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<title>Subduction – JOIDES Resolution</title>
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<item>
<title>Taking the Pulse of Subduction: Dr. Fryer</title>
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<dc:creator><![CDATA[Martin Bottcher]]></dc:creator>
<pubDate>Sun, 29 Jan 2017 00:50:10 +0000</pubDate>
<category><![CDATA[EXP366]]></category>
<category><![CDATA[serpentine]]></category>
<category><![CDATA[Subduction]]></category>
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<description><![CDATA[One of the two Co-Chief-scientists of Expedition 366 is Patty Fryer, a Professor of Geology at the University of Hawaii.... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/taking-the-pulse-of-subduction-dr-fryer/" title="Continue reading Taking the Pulse of Subduction: Dr. Fryer">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
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<p style="margin-top: 0.3em; margin-bottom: 9pt;"><span style="color: #000072; font-family: Georgia; font-size: 19px;">One of the two Co-Chief-scientists of Expedition 366 is Patty Fryer, a Professor of Geology at the University of Hawaii. She is mainly concerned with plate-tectonics, the metamorphism of supra-subduction zone regions and the associated production of serpentine mud and other geochemical cycles.</span></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt; text-align: justify;"><img fetchpriority="high" decoding="async" class="alignnone size-full wp-image-23191" src="https://joidesresolution.org//wp-content/uploads/2017/01/PF2.jpg" alt="" width="640" height="480" srcset="https://joidesresolution.org/wp-content/uploads/2017/01/PF2.jpg 640w, https://joidesresolution.org/wp-content/uploads/2017/01/PF2-300x225.jpg 300w" sizes="(max-width: 640px) 100vw, 640px" /></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt; text-align: justify;"><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;">Photo:Co-Chief- Scientists: Patty Fryer and Geoffrey Wheat</span></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt; text-align: justify;"><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;">When one summarizes the times Patty Fryer has spent on research vessels exploring the earth under the sea, it turns out that it has been more than three years. Among these expeditions have been really striking ones, like the first use of the ROV (remotely operated vehicle) Nereus for a test in Hawaii in 2008 and the exploration of the Challenger Deep in 2009 with it. In 2012 Patty came back to the Challenger Deep together with James Cameron, to advise further exploration of Earth’s deepest point under the sea. Why then is she going one more time at sea with IODP Expedition 366 on board of the JOIDES Resolution? </span></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt; text-align: justify;"><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;">There is a clear answer to this: “To take the pulse of subduction”. She explains to me, that earthquakes at suduction zones like the Mariana Convergent Margin likely correlate with fluid releases out of the down -going plate, which cause eruptions of the serpentinite mud volcanoes, like the ones we are exploring on this expedition. Patty outlines the option of a future monitoring of earthquake and mud-volcano-eruptions based on the drill-holes at three mud-volcanoes that we equipped with screened casings during our expedition. </span></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt; text-align: justify;"><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;">One may ask, if there are any secrets to be expected in the blue-green serpentinite mud. Patty is sure, that there are some. For example the color itself is unexplained. Furthermore, she expects more information about how life may have come into existence on the early Earth. Focus on that research has shifted from hydrothermal systems at mid-ocean ridges to subduction zones, mainly because of the cooler temperatures, the highly reducing conditions and the availability of hydrogen and methane. </span></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt; text-align: justify;"><img decoding="async" class="alignnone size-full wp-image-23192" src="https://joidesresolution.org//wp-content/uploads/2017/01/ProfPF3.jpg" alt="" width="640" height="640" srcset="https://joidesresolution.org/wp-content/uploads/2017/01/ProfPF3.jpg 640w, https://joidesresolution.org/wp-content/uploads/2017/01/ProfPF3-150x150.jpg 150w, https://joidesresolution.org/wp-content/uploads/2017/01/ProfPF3-300x300.jpg 300w" sizes="(max-width: 640px) 100vw, 640px" /></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt; text-align: justify;"><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;">Photo: Blue Serpentinite Mud</span></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt; text-align: justify;"><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;">Has she imagined before drilling into the seafloor, what might be going on down there, is my next question. Sure she has. She can almost see the fluids being released during an earthquake on the top of the down-going Pacific plate, rising along the ground-up faces of faults, invading the surrounding rocks like grasping fingers, turning everything it touches to serpentine, and rising as a mush through the mud volcano conduits to burp, or flow out onto the seafloor and form monstrous mounds of mud. One believes, that for a visionary Geologist like her the thrill of discovery will never end. </span></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt;"><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;">Finally I want to know, if in her opinion the knowledge of geosciences increases respect for nature in the scientist himself. “Absolutely yes”, Patty says, “in so many ways. It makes us feel so small when we realize the grandure of nature and see, how interrelated all the fields of science are. How can you not love nature, when you learn more and more about it”?</span></p>
<p style="margin-top: 0.3em; margin-bottom: 9pt;"><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;">So it seems to me, that Dr. Patty Fryer is not only taking the pulses of subduction, but also sensitive to different other pulses of the Earth.</span></p>
<div><span lang="EN-US" style="font-size: 14pt; font-family: Georgia; color: #000072;"> </span></div>
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</item>
<item>
<title>Incoming! Oblique Subduction at the Sunda Subduction Zone</title>
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<dc:creator><![CDATA[Naomi Barshi]]></dc:creator>
<pubDate>Sun, 25 Sep 2016 20:05:30 +0000</pubDate>
<category><![CDATA[earthquakes_659]]></category>
<category><![CDATA[EXP362]]></category>
<category><![CDATA[Expedition 362 Sumatra Seismogenic Zone]]></category>
<category><![CDATA[Plate-Tectonics]]></category>
<category><![CDATA[strike-slip fault]]></category>
<category><![CDATA[Subduction]]></category>
<category><![CDATA[subduction zone]]></category>
<category><![CDATA[subduction zones]]></category>
<category><![CDATA[tectonics]]></category>
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<description><![CDATA[The Indian and Australian Plates plow northeast into the Sumatra subduction zone, part of the larger Sunda subduction zone, at a... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/incoming-oblique-subduction-at-the-sunda-subduction-zone/" title="Continue reading Incoming! Oblique Subduction at the Sunda Subduction Zone">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p class="p1">The Indian and Australian Plates plow northeast into the Sumatra subduction zone, part of the larger Sunda subduction zone, at a speed of 45 mm/yr. The angle between the direction these two plates move relative to each other is not always at a right angle (90°) to the subduction zone itself–here it is about 50°. Sliding under the Sunda Plate at an angle is not easy, so several large strike-slip fault systems help to accommodate some of this movement. If you thought learning vectors in high school was pointless—think again. This is a perfect vector component problem!</p>
<p>Before we get to big words about big faults, let’s review vectors. If you want to walk from one corner of an intersection to the corner diagonally across from you, you typically go along one side of the intersection, wait for the pedestrian light, and then walk the other side. You’ve walked two sides of a triangle to get to your destination. The third side of the triangle is the line that connects your start and end points:</p>
<p><img decoding="async" class="alignnone size-full wp-image-23600" src="https://joidesresolution.org//wp-content/uploads/2016/09/roadCross.png" alt="" width="306" height="244" srcset="https://joidesresolution.org/wp-content/uploads/2016/09/roadCross.png 306w, https://joidesresolution.org/wp-content/uploads/2016/09/roadCross-300x239.png 300w" sizes="(max-width: 306px) 100vw, 306px" /></p>
<p> </p>
<p class="p1">Each side of the triangle is a vector, and we can think of the two pedestrian crossings as components (purple lines/arrows) of the vector that connects your start and end points (orange line/arrow). A vector is a quantity that has a magnitude (in this case length, the distance across the intersection = 20m) and a direction (NW). Any vector can be broken down into component lengths and directions at right angles, like the two sides of the intersection that you just walked.</p>
<p class="p1">The motion of the Indian Plate coming into the North Sumatran subduction zone is also a vector. We can break it down into two components: one parallel to the subduction zone (yellow arrow on map below) and one perpendicular to the subduction zone (orange red arrow). Because the Indian/Australian plate comes in at an angle other than 90º to the subduction zone, we call it “oblique subduction”. (Plate motion vectors and fault locations adapted from Meltzner et al., 2012.)</p>
<p><img loading="lazy" decoding="async" class="alignnone size-full wp-image-23602" src="https://joidesresolution.org//wp-content/uploads/2016/09/subductvectors.jpg" alt="" width="640" height="462" srcset="https://joidesresolution.org/wp-content/uploads/2016/09/subductvectors.jpg 640w, https://joidesresolution.org/wp-content/uploads/2016/09/subductvectors-300x217.jpg 300w" sizes="auto, (max-width: 640px) 100vw, 640px" /></p>
<p>The main subduction zone thrust fault takes up primarily the NE-directed motion of the Indian Plate, perpendicular to the subduction zone. That is, the orange red component of the plate motion vector is taken up by earthquakes on the subduction zone that allow the plates to move past each other. Here are two models that show the motion of the plates during the 2004 M 9.2 Great Sumatra-Andaman Islands Earthquake. During the earthquake the plate overlying the subduction zone actually rebounded towards the SW, over the down-going Indian Plate. Notice that the arrows (from GPS measurements of ground motion change before and after the earthquake) point almost directly across the subduction zone at 90º (models from Chlieh et al., 2007, and Rhie et al., 2007).</p>
<p><img loading="lazy" decoding="async" class="alignnone size-full wp-image-23601" src="https://joidesresolution.org//wp-content/uploads/2016/09/RuptureGPS.jpg" alt="" width="640" height="599" srcset="https://joidesresolution.org/wp-content/uploads/2016/09/RuptureGPS.jpg 640w, https://joidesresolution.org/wp-content/uploads/2016/09/RuptureGPS-300x281.jpg 300w" sizes="auto, (max-width: 640px) 100vw, 640px" /></p>
<p class="p2">But there is still plate motion to account for in the system: the yellow component of the overall plate motion. Faults parallel to the subduction zone take up the slack – This is fairly common in subduction zones because plates rarely meet exactly head on. These long, subduction zone-parallel faults are strike-slip faults. They’re nearly vertical in the subsurface, and motion along them can be seen looking straight down, as if looking at a map. The San Andreas Fault is a well-known example of a strike-slip fault that lets the Pacific Plate move north along the North American Plate. In Sumatra, the primary fault taking up this motion is the Great Sumatran Fault which runs along the center of the island of Sumatra. In fact, the fault runs very close to the volcanic arc of the subduction zone. The southwestern side of the fault moves to the northwest, the same direction as the plate motion not accounted for by subduction. There are also other strike-slip faults offshore, also parallel to the subduction zone, which help to take up some of this plate motion. This figure shows different historic and recent earthquakes in the Sumatra region, including along the Great Sumatran Fault, parallel to the Sunda Trench (Fig. 10 in McCaffrey, 2009).</p>
<p> </p>
<p><img loading="lazy" decoding="async" class="alignnone size-full wp-image-23598" src="https://joidesresolution.org//wp-content/uploads/2016/09/McCaffrey_SumatraFig.jpg" alt="" width="640" height="276" srcset="https://joidesresolution.org/wp-content/uploads/2016/09/McCaffrey_SumatraFig.jpg 640w, https://joidesresolution.org/wp-content/uploads/2016/09/McCaffrey_SumatraFig-300x129.jpg 300w" sizes="auto, (max-width: 640px) 100vw, 640px" /></p>
<p> </p>
<p class="p2">The Great Sumatran Fault carries its own seismic hazard that adds to the risk posed by subduction zone earthquakes and tsunami. On top of the seismic hazard, the southwestern and southern coast of Sumatra and Java host many active volcanoes. The volcanoes are also part of the subduction zone system: they are fed by molten material from the mantle because of the ocean crust subducting below. (That’s another post for another time!)</p>
<p class="p2">Here’s a map of the seismic hazard of Indonesia and Malaysia that shows the maximum amount the ground is likely to move during earthquake shaking in the next 50 years. “How much” is expressed as peak ground acceleration, in percent of the normal acceleration caused by gravity. “Likely” is a 10% chance that the ground will move that much during the 50 year time period. (Map created by the USGS based on data from a variety of sources. See Further Reading for full map poster with citations.)</p>
<p> </p>
<p><img loading="lazy" decoding="async" class="alignnone size-full wp-image-23603" src="https://joidesresolution.org//wp-content/uploads/2016/09/SumSeismHazUSGS.jpg" alt="" width="640" height="565" srcset="https://joidesresolution.org/wp-content/uploads/2016/09/SumSeismHazUSGS.jpg 640w, https://joidesresolution.org/wp-content/uploads/2016/09/SumSeismHazUSGS-300x265.jpg 300w" sizes="auto, (max-width: 640px) 100vw, 640px" /></p>
<p> </p>
<p class="p1">This type of plate boundary geometry is not unique to the Sumatra region. In many plate boundaries where plates converge at an angle rather moving straight toward each other, we see that long strike-slip fault systems help to take up the overall plate motion. The Liquine-Ofqui Fault and Atacama Fault serve a similar purpose in the Andean subduction zone in Chile. The Median Tectonic Line is the largest strike-slip fault in Japan and accounts for the oblique motion at the Nankai subduction zone. Learning about processes at one site on Earth can help us understand what’s going on elsewhere in the world!</p>
<p class="p1"><strong>Sources and Further Reading</strong></p>
<p class="p1"><u>General information</u></p>
<p class="p1"><u>Journal articles</u></p>
<p class="p1">Baroux et al., 1998. Slip-partitioning and fore-arc deformation at the Sunda Trench, Indonesia. Terra Nova, 10 (3), 139-144.</p>
<p class="p1">Bellier and Sébrier, 1995. Is the slip rate variation on the Great Sumatran Fault accommodated by fore-arc stretching? Geophysical Research Letters, 22 (15), 1969-1972.</p>
<p class="p1">Berglar et al., 2010. Structural evolution and strike-slip tectonics off north-western Sumatra. Tectonophysics 480, 119-132.</p>
<p class="p1">Chlieh, M., Avouac, J.-P., Hjorleifsdottir, V., Song, T.-R.A., Ji, C., Sieh, K., Sladen, A., Hebert, H., Prawirodirdjo, L., Bock, Y., and Galetzka, J., 2007. Coseismic slip and afterslip of the great (Mw 9.15) Sumatra-Andaman earthquake of 2004. Bulletin of the Seismological Society of America, 97(1A):S152–S173. <a href="http://dx.doi.org/10.1785/0120050631">http://dx.doi.org/10.1785/0120050631<</a></p>
<p class="p1">Fitch, T.J., 1972. Plate convergence, transcurrent faults, and internal deformation adjacent to Southeast Asia and the Western Pacific. Journal of Geophysical Research 77 (23), 4432–4460. <a href="http://onlinelibrary.wiley.com/doi/10.1029/JB077i023p04432/epdf" class="broken_link">doi:10.1029/JB077i023p04432<</a></p>
<p class="p1">McCaffrey, R., 2009. The Tectonic Framework of the Sumatran Subduction Zone, Annual Reviews in Earth and Planetary Sciences, 37, 345-366.</p>
<p class="p1">Meltzner, A. J., K. Sieh, H.-W. Chiang, C.-C. Shen, B. W. Suwargadi, D. H. Natawidjaja, B. Philibosian, and R. W. Briggs, 2012. Persistent termini of 2004- and 2005-like ruptures of the Sunda megathrust, Journal of Geophysical Research, 117, B04405,</p>
<p class="p1">Rhie, J., Dreger, D., Bürgmann, R., and Romanowicz, B., 2007. Slip of the 2004 Sumatra-Andaman earthquake from <dfn title="Look up the definition of Joint.">joint</dfn> inversion of long-period global seismic waveforms and GPS static offsets. Bulletin of the Seismological Society of America, 97(1A):S115–S127. <a href="http://dx.doi.org/10.1785/0120050620">http://dx.doi.org/10.1785/0120050620<</a></p>
<p> </p>
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<item>
<title>What is a subduction zone?</title>
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<dc:creator><![CDATA[Agnes Pointu]]></dc:creator>
<pubDate>Sat, 27 Aug 2016 04:21:59 +0000</pubDate>
<category><![CDATA[EXP362]]></category>
<category><![CDATA[lithosphere plates prism Subduction]]></category>
<category><![CDATA[lithosphere_683]]></category>
<category><![CDATA[plates]]></category>
<category><![CDATA[prism]]></category>
<category><![CDATA[Subduction]]></category>
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<description><![CDATA[If you look for the position of the JOIDES Resolution on Google, you will find that we are actually drilling... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/what-is-a-subduction-zone/" title="Continue reading What is a subduction zone?">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p align="justify">If you look for the position of the <em>JOIDES Resolution</em> on Google, you will find that we are actually drilling into the seafloor near a subduction zone (the Sumatra or Sunda subduction zone). The deepwater part of the subduction zone is sometimes called a trench. Since the 1960s, everybody accepts the idea that the lithosphere (the rigid, outermost shell of the planet) is made of plates and that these plates move relative to each other. And sometimes, they meet each other….</p>
<p align="center"><img decoding="async" style="border: 0px solid; margin: 0px;" src="/sites/default/files/u376/Map_of_the_Sumatra_Trench.jpg" alt="Map_of_the_Sumatra_Trench" /></p>
<p align="center"><span style="font-size: xx-small;"><em>Image from Wikipedia </em></span></p>
<p align="justify"><strong>What is happening then?</strong></p>
<p align="justify">One of the plates is denser and thinner than the other. When the two plates face off, the denser plate (here the Indo-Australian plate) will move underneath the less dense Sunda plate and stard to bend down into the mantle (at an average rate of 4 to 6 cm every year). But it’s not easy for many reasons: first, the plate is very tough, second it is carrying a thickness of sediments (up to 5 km) which are less dense than the igneous crust and don’t want to be buried (too young for that!). A tectonic fault is formed between the two plates and the movement between the two plates happens on this fault. Most of the time, there is no movement on the fault and it is stuck for many years (often hundreds of years). But when this stuck area moves, it moves very fast and all of the energy that has been building up for many years is released in a very short time–this makes an earthquake. This was the case in 2004 when a magnitude >9 earthquake struck North Sumatra and the Adaman -Nicobar islands. The earthquake moved the seafloor and this made a tsunami, which killed over 250,000 people around the Indian Ocean. Although rare at any one place on Earth on human timescales, over geologic time earthquakes are frequent in subduction zones.</p>
<p align="justify"><strong>What makes subduction zones special?</strong></p>
<p align="center"><img decoding="async" style="border: 0px solid; margin: 5px;" src="/sites/default/files/u375/TectonicSetting.png" alt="TectonicSetting" /></p>
<p align="justify">The map reveals typical features of a classic subduction zone: a deepwater oceanic trench, a forearc prism, and an island arc. The Sunda Trench marks the location of the plate boundary at the seafloor, where the oceanic plate (the Indian-Australaian plate) meets the continental plate (the Sunda plate). The very thick sediments on the oceanic Indian-Australian plate are scraped off, forming an accretionary wedge. A series of islands are the crest of this wedge. The ridge is formed primarily from these marine sediments scraped off the oceanic plate and piled up on top of the leading edge of the continental Sunda Plate.</p>
<p align="justify">And it is that wedge which makes this subduction zone special. First, the structure and shape of the forearc changes a lot along the subduction zone form north to south (prism width, slope, prism fault dip…). The sediments offshore North Sumatra are very thick (due to the Bengal-Nicobar fan sediment system) and thicker than other places along the subduction zone. Additionally the rate at which the plates move towards each other also changes along the subduction zone. Earthquakes are expected in subduction zones, but the 2004 earthquake ruptured to much shallower depths and closer to trench than most other subduction zone earthquakes and ended in the accretionary prism. Scientists made similar observations for the Japan Tohoku-Oki earthquake in 2011 (remember the Fukushima disaster). In Sumatra, scientists are thinking that the changes in structure and shape of the forearc and of the unusual type of earthquake may have the same cause: the very thick sediments. Earthquakes are not destructive when they are small, and even large ones may not be destructive if they occur deep in Earth’s crust and/or far from inhabited places. However, when they are large, shallow, and occur near population centers, they can be very dangerous. Their effects can be even more devastating when they occur under the ocean floor. In this case, they can trigger a tsunami, especially when they are shallow.</p>
<p align="justify"><strong>How can we explain these shallow earthquakes?</strong></p>
<p align="justify">The properties of the sediments involved in the subduction zone in North Sumatra may be a part of the answer. This is one of the goals of the IODP 362 expedition: to characterize more precisely the physical properties, chemistry, and geological properties of the sediments on the oceanic Indian-Australian plate where they can be reached by drilling, before they get involved in the plate boundary fault where they generate earthquakes and tsunamis.</p>
<p align="justify">Thanks to Naomi for helping me in adjusting the picture!</p>
<p align="justify">For my blog in french: https://expedition362joides.wordpress.com/</p>
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<title>Houston, we've landed on….Boninite</title>
<link>https://joidesresolution.org/houston-weve-landed-on-boninite/?utm_source=rss&utm_medium=rss&utm_campaign=houston-weve-landed-on-boninite</link>
<comments>https://joidesresolution.org/houston-weve-landed-on-boninite/#respond</comments>
<dc:creator><![CDATA[Amy West]]></dc:creator>
<pubDate>Sun, 10 Aug 2014 04:04:19 +0000</pubDate>
<category><![CDATA[boninite]]></category>
<category><![CDATA[EXP352]]></category>
<category><![CDATA[forearc]]></category>
<category><![CDATA[IODP]]></category>
<category><![CDATA[mariana trench]]></category>
<category><![CDATA[scientific drilling]]></category>
<category><![CDATA[Subduction]]></category>
<category><![CDATA[thin-section]]></category>
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<title>Geek Blog, entry 1: Some of the science behind my Leg 352 participation….</title>
<link>https://joidesresolution.org/geek-blog-entry-1-some-of-the-science-behind-my-leg-352-participation/?utm_source=rss&utm_medium=rss&utm_campaign=geek-blog-entry-1-some-of-the-science-behind-my-leg-352-participation</link>
<comments>https://joidesresolution.org/geek-blog-entry-1-some-of-the-science-behind-my-leg-352-participation/#respond</comments>
<dc:creator><![CDATA[Jeff Ryan]]></dc:creator>
<pubDate>Fri, 08 Aug 2014 21:46:10 +0000</pubDate>
<category><![CDATA[earthquakes_659]]></category>
<category><![CDATA[EXP352]]></category>
<category><![CDATA[Subduction]]></category>
<category><![CDATA[volcanoes_285]]></category>
<category><![CDATA[water]]></category>
<guid isPermaLink="false">https://joidesresolution.org//geek-blog-entry-1-some-of-the-science-behind-my-leg-352-participation</guid>
<description><![CDATA[]]></description>
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