The flow of crystal-bearing magmas.

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“穹顶”，位于火山顶部。这类火山的喷发突然转变为高爆炸性的喷发是很常见的，这要危险得多。目前，我们无法准确预测这种转变何时会发生，这对生活在这些火山附近的人来说是一个问题。我们现在认为，这种转换主要是由岩浆中生长的晶体的影响引起的。这些晶体使岩浆变得更粘性，也就是说，更粘性，所以它不会那么容易流动。岩浆变得僵硬，形成了一个堵塞上升的岩浆路径的塞子。堵塞导致火山内的压力上升。最终，压力变得如此之大，以至于塞子被摧毁，并发生猛烈的爆炸。如果我们想要准确地描述这一过程，那么我们需要知道岩浆中的晶体如何改变岩浆流动的方式。我们在这里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，在这些实验中，我们将在液体中产生固体颗粒(而不是晶体)的混合物。我们将使用一种名为“流变仪”的仪器来测量这些混合物的粘度(即它们有多容易流动或有多“粘滞”)。我们将使用的特殊流变仪上装有显微镜，因此我们将能够看到颗粒是如何运动的。能够看到这一点尤其重要，因为随着混合物的流动，颗粒会四处移动。当颗粒移动时，它们有时会排成一条线，或形成团块，这会影响粘度。我们认为，重要的是要看到混合物流动时内部颗粒发生了什么，这样我们就可以将其与测量的粘度联系起来。我们将使用实验室实验的结果来建立描述混合物粘度的方程，以便可以计算颗粒/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，我们就会对岩浆流动的方式有一些新的了解。然后，我们将使用我们产生的方程来计算计算机模型中含有晶体的岩浆的粘度，这些计算机模型试图预测岩浆如何喷发，特别是从缓慢、非爆炸性喷发到猛烈、高度爆炸性喷发的转换。这将使我们能够看到是什么控制了火山喷发的行为，并将有助于使数值模型的输出对火山喷发的预测有用。

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.