The flow of crystal-bearing magmas.

含有晶体的岩浆流。

• 批准号: NE/D003091/1
• 负责人: Heidy Mader
• 金额: $ 30.27万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FD003091%2F1
• 关键词: flow; crystal; bearing; magmas.

Many volcanoes erupt magma slowly and non-explosively for a long period of time. The magma is often piled up as a 'dome' that sits at the top of the volcano. It is quite common for the eruption at such volcanoes suddenly to switch to a highly-explosive type of eruption, which is much more dangerous. At the moment we cannot predict accurately when such a switch will occur, which is a problem for the people who live near such volcanoes. We now think that the switchings are caused mainly by effects of crystals growing in the magma. The crystals make the magma more viscous, that is, more 'sticky', so it doesn't flow so easily. The magma becomes rigid and forms a plug which blocks the path for the rising magma. The blockage causes the pressure to rise in the volcano. Eventually, the pressure becomes so great that the plug is destroyed and a violent explosion occurs. If we want to be able to describe this process accurately, then we need to know how crystals in the magma change the way the magma flows. The project that we are planning here will address this problem. We will conduct a series of laboratory experiments in which we will produce mixtures of solid particles (in place of crystals) in a liquid. We will measure the viscosity of these mixtures (i.e. how easily they flow or how 'sticky' they are) using an instrument called a 'rheometer'. The particular rheometer we will use has a microscope attached to it, so we will be able to see how the particles are moving. It is particularly important to be able to see this because the particles move around as the mixture flows. As the particles move, they sometimes line up, or form clumps and this affects the viscosity. We think it will be important to see what is happening to the particles inside the mixture as it flows so that we can relate this to the measured viscosity. We will use the results of the laboratory experiments to produce equations that describe the viscosity of the mixtures so that it will be possible to calculate the viscosity of the particle/liquid mixture, rather than measure it. This is interesting because, if we manage to do this, we will have understood something new about the way magma flows. We will then use the equations we have produced to calculate the viscosity of a magma that contains crystals in computer models that try to predict how magmas erupt and especially the switchings from slow, non-explosive to violent, highly-explosive eruptions. This will allow us to see what controls the behaviour and, will help to make the outputs from the numerical models useful for the prediction of volcanic eruptions.

许多火山在很长一段时间内缓慢地、非爆炸性地喷发岩浆。岩浆通常堆积成一个位于火山顶部的“圆顶”。这是很常见的火山喷发突然切换到一个高爆炸性的喷发类型，这是更危险的。目前，我们还不能准确地预测这种转变何时发生，这对生活在火山附近的人们来说是一个问题。我们现在认为，这种转换主要是由岩浆中晶体生长的影响造成的。晶体使岩浆更粘稠，也就是说，更“粘”，所以它不那么容易流动。岩浆变得坚硬，形成一个塞子，挡住了岩浆上升的路径。堵塞导致火山内压力上升。最后，压力变得如此之大，以至于塞子被破坏，并发生剧烈爆炸。如果我们想准确地描述这个过程，那么我们需要知道岩浆中的晶体如何改变岩浆的流动方式。我们正在计划的项目将解决这个问题。我们将进行一系列实验室实验，在实验中我们将在液体中产生固体颗粒（代替晶体）的混合物。我们将使用一种称为“流变仪”的仪器来测量这些混合物的粘度（即它们流动的容易程度或它们的“粘性”）。我们将使用的特定流变仪上有一个显微镜，所以我们能够看到颗粒是如何移动的。能够看到这一点特别重要，因为颗粒随着混合物流动而四处移动。当粒子移动时，它们有时会排成一行，或形成团块，这会影响粘度。我们认为，观察混合物流动时内部的颗粒发生了什么变化是很重要的，这样我们就可以将其与测量的粘度联系起来。我们将利用实验室实验的结果来建立描述混合物粘度的方程，这样就可以计算颗粒/液体混合物的粘度，而不是测量它。这很有趣，因为如果我们设法做到这一点，我们将对岩浆流动的方式有新的了解。然后，我们将使用我们已经产生的方程来计算包含晶体的岩浆的粘度，这些晶体用于计算机模型，试图预测岩浆如何喷发，特别是从缓慢，非爆炸性到剧烈，高爆炸性喷发的转换。这将使我们能够看到是什么控制了这种行为，并将有助于使数值模型的输出对预测火山爆发有用。