探花直播 of Cambridge - Euan Mutch
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en鈥楥rystal clocks鈥� used to time magma storage before volcanic eruptions
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<div class="field field-name-field-news-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even"><img class="cam-scale-with-grid" src="/sites/default/files/styles/content-580x288/public/news/research/news/crop_126.jpg?itok=7d0R5Z_V" alt="Magma erupting at the Holuhraun lava field in August 2014" title="Magma erupting at the Holuhraun lava field in August 2014, Credit: Bob White" /></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Researchers from the 探花直播 of Cambridge used volcanic minerals known as 鈥榗rystal clocks鈥� to calculate how long magma can be stored in the deepest parts of volcanic systems. This is the first estimate of magma storage times near the boundary of the Earth鈥檚 crust and the mantle, called the Moho. 探花直播<a href="https://doi.org/10.1126/science.aax4092">results</a> are reported in the journal <em>Science</em>.</p>
<p>鈥淭his is like geological detective work,鈥� said Dr Euan Mutch from Cambridge鈥檚 Department of Earth Sciences, and the paper鈥檚 first author. 鈥淏y studying what we see in the rocks to reconstruct what the eruption was like, we can also know what kind of conditions the magma is stored in, but it鈥檚 difficult to understand what鈥檚 happening in the deeper parts of volcanic systems.鈥�</p>
<p>鈥淒etermining how long magma can be stored in the Earth鈥檚 crust can help improve models of the processes that trigger volcanic eruptions,鈥� said co-author Dr John Maclennan, also from the Department of Earth Sciences. 鈥� 探花直播speed of magma rise and storage is tightly linked to the transfer of heat and chemicals in the crust of volcanic regions, which is important for geothermal power and the release of volcanic gases to the atmosphere.鈥�</p>
<p> 探花直播researchers studied the Borgarhraun eruption of the Theistareykir volcano in northern Iceland, which occurred roughly 10,000 years ago, and was fed directly from the Moho. This boundary area plays an important role in the processing of melts as they travel from their source regions in the mantle towards the Earth鈥檚 surface. To calculate how long the magma was stored at this boundary area, the researchers used a volcanic mineral known as spinel like a tiny stopwatch or crystal clock.</p>
<p>Using the crystal clock method, the researchers were able to model how the composition of the spinel crystals changed over time while the magma was being stored. Specifically, they looked at the rates of diffusion of aluminium and chromium within the crystals and how these elements are 鈥榸oned鈥�.</p>
<p>鈥淒iffusion of elements works to get the crystal into chemical equilibrium with its surroundings,鈥� said Maclennan. 鈥淚f we know how fast they diffuse we can figure out how long the minerals were stored in the magma.鈥�</p>
<p> 探花直播researchers looked at how aluminium and chromium were zoned in the crystals and realised that this pattern was telling them something exciting and new about magma storage time. 探花直播diffusion rates were estimated using the results of previous lab experiments. 探花直播researchers then used a new method, combining finite element modelling and Bayesian nested sampling to estimate the storage timescales.</p>
<p>鈥淲e now have really good estimates in terms of where the magma comes from in terms of depth,鈥� said Mutch. 鈥淣o one鈥檚 ever gotten this kind of timescale information from the deeper crust.鈥�</p>
<p>Calculating the magma storage time also helped the researchers determine how magma can be transferred to the surface. Instead of the classical model of a volcano with a large magma chamber beneath, the researchers say that instead, it鈥檚 more like a volcanic 鈥榩lumbing system鈥� extending through the crust with lots of small 鈥榮pouts鈥� where magma can be quickly transferred to the surface.</p>
<p>A <a href="https://www.nature.com/articles/s41561-019-0376-9">second paper</a> by the same team, recently published in <em>Nature Geoscience</em>, found that that there is a link between the rate of ascent of the magma and the release of CO2, which has implications for volcano monitoring.</p>
<p> 探花直播researchers observed that enough CO2 was transferred from the magma into gas over the days before eruption to indicate that CO2 monitoring could be a useful way of spotting the precursors to eruptions in Iceland. Based on the same set of crystals from Borgarhraun, the researchers found that magma can rise from a chamber 20 kilometres deep to the surface in as little as four days.</p>
<p> 探花直播research was supported by the Natural Environment Research Council (NERC).</p>
<p><em><strong>References:</strong></em><br /><em>Euan J.F. Mutch et al. 鈥�<a href="https://doi.org/10.1126/science.aax4092">Millennial storage of near-Moho magma</a>.鈥� Science (2019). DOI: 10.1126/science.aax4092</em></p>
<p><em>Euan J.F. Mutch et al. 鈥�<a href="https://www.nature.com/articles/s41561-019-0376-9">Rapid transcrustal magma movement under Iceland</a>.鈥� Nature Geoscience (2019). DOI: 10.1038/s41561-019-0376-9</em></p>
</div></div></div><div class="field field-name-field-content-summary field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><p> 探花直播molten rock that feeds volcanoes can be stored in the Earth鈥檚 crust for as long as a thousand years, a result which may help with volcanic hazard management and better forecasting of when eruptions might occur.</p>
</p></div></div></div><div class="field field-name-field-content-quote field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even">This is like geological detective work</div></div></div><div class="field field-name-field-content-quote-name field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Euan Mutch</div></div></div><div class="field field-name-field-image-credit field-type-link-field field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/" target="_blank">Bob White</a></div></div></div><div class="field field-name-field-image-desctiprion field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Magma erupting at the Holuhraun lava field in August 2014</div></div></div><div class="field field-name-field-cc-attribute-text field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><a href="http://creativecommons.org/licenses/by/4.0/" rel="license"><img alt="Creative Commons License" src="https://i.creativecommons.org/l/by/4.0/88x31.png" style="border-width:0" /></a><br />
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</div></div></div><div class="field field-name-field-show-cc-text field-type-list-boolean field-label-hidden"><div class="field-items"><div class="field-item even">Yes</div></div></div>Thu, 18 Jul 2019 18:00:00 +0000sc604206632 at