Collaborative Research: How faithfully are melt embayments wedded to magma ascent?

火山爆发会造成广泛的社会影响。火山喷发的爆炸性部分是由岩浆在管道中上升的速度控制的。直接测量岩浆上升是一项挑战，因为它发生在地下，而且环境危险。被冻结在晶体中的岩浆的小气泡，被称为embayments，可能以化学扩散梯度的形式保存了上升速率的记录，科学家可以将其作为一种岩浆速度计。这种探测技术已越来越多地用于了解古代火山爆发的动力学。随着这种速度计技术越来越受欢迎，验证其准确性非常重要。在这里，在岩浆温度和压力下进行的一系列实验室实验将重现岩浆在受控条件下的上升过程，以测试洞穴对这一过程的记录。仔细比较受控的实验室条件和实验井的扩散梯度将澄清“如果”和“如何”井忠实地记录岩浆上升。研究生和本科生将在纽约市立大学和贝勒大学接受研究方法方面的培训。此外，将在国家自然历史博物馆和纽约虚拟火山观测站以“科学家在”会议和岩浆上升的短形式教育视频的形式进行公众宣传。量化火山导管中岩浆上升的速率对于了解火山喷发的时间、规模和行为至关重要。保存在洞穴内的淬火的熔体袋被认为保存了由扩散平衡控制的成分梯度等速率。过去的研究使用钻孔来确定岩浆上升速率，使用了一些精心挑选的样本，并做出了合理但未经检验的假设，包括扩散和减压途径。埋藏地质测速法的关键假设必须经过实验验证，才能自信地用于推进对火山喷发动力学的理解。在这里，将针对集中的天然样品套件和使用天然和合成弹孔的一系列减压实验，系统地测试弹孔地质测速的理论基础。重要的测试包括(1)发现一个单独的岩洞在多大程度上代表了一批岩浆，以及(2)观察到的扩散曲线是否与实验条件和关键假设预测的相匹配。如果实验结果是可靠的，那么地质测速法将成为了解火山导管在喷发时状况的一个有价值的工具。如果实验扩散曲线显示与实验条件预测的不匹配，那么实验将为探索实验记录的复杂性提供一个经验框架。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Explosive eruptions can cause wide-ranging societal impacts. The explosivity of a volcanic eruption is controlled in part by how fast magma rises in the conduit. Directly measuring magma ascent is challenging because it takes place underground and in a dangerous environment. Small blebs of frozen magma trapped in crystals, called embayments, may preserve a record of ascent rate in the form of chemical diffusion gradients that scientists can apply as a kind of magma speedometer. This embayment technique has been increasingly used to understand the dynamics of ancient volcanic eruptions. As this speedometer technique grows in popularity, validating its accuracy is important. Here, a series of laboratory experiments conducted using real magma at magmatic temperatures and pressures will recreate magma ascent under controlled conditions to test how well embayments record this process. Careful comparison between the controlled lab conditions and the diffusion gradients in the experimental embayments will clarify “if” and “how?” embayments faithfully record magmatic ascent. Graduate and undergraduate students will be trained in research methods at CUNY and Baylor. In addition, public outreach will be performed at the National Museum of Natural History and the NY Virtual Volcano Observatory in the form of “Scientist-is-In” sessions and short-format educational videos on magma ascent. Quantifying the rate of magma ascent in the volcanic conduit is critical to understanding the timing, magnitude, and behavior of eruptions. Quenched pockets of melt preserved within embayments are thought to preserve such rates as compositional gradients controlled by diffusive equilibration. Past studies using embayments to determine magma ascent rates have used a few, carefully selected samples and have made reasonable, but untested, assumptions involving diffusion and decompression pathway. The key assumptions underlying embayment geospeedometry must be experimentally validated before it can be confidently used to advance the understanding of volcanic eruption dynamics. Here, the theoretical basis for embayment geospeedometry will be systematically tested against focused suites of natural samples and a series of decompression experiments using natural and synthetic embayments. Important tests include (1) discovering how well a single embayment represents a batch of magma, and (2) whether observed diffusion profiles match those predicted from experimental conditions and key assumptions. If the experimental embayments are shown to be robust, then embayment geospeedometry will become a valuable tool for understanding the conditions in volcanic conduits during eruption. If experimental diffusion profiles are instead shown to not match those predicted by experimental conditions then the experiments will provide an empirical framework for exploring the complexities recorded by embayments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.