Eruption of high silica rhyolites - Textural Analysis

火山岩是由S数十公里深处产生的岩浆形成的。岩浆通常非常粘稠，富含天然气。气体从非常粘稠的岩浆中分离和逸出的方式控制着喷发是喷发的还是爆炸性的，就像打开香槟酒瓶时气体可以从液体中分离出来一样。粘性岩浆在上升过程中冷却，产生各种矿物，如石英和长石。正如加拿大人第一手了解并认识到从云中以冰的形式降落的各种不同的结晶形式一样，我们知道这些火山系统的矿物根据其形成条件形成不同的模式。通过对这些矿物模式的研究，我们能够推断出一些关于导致喷发的深层过程性质的信息。

Volcanic rocks are formed from magma produced at depths of many 10's of km. The magma is often extremely viscous and gas-rich. The way in which the gas separates and escapes from very viscous magma controls whether eruption is effusive or explosive, in like manner to the way which gas can be un-mixed from the liquid upon opening a champagne bottle. Viscous magmas cool during their ascent producing a variety of minerals such as quartz and feldspar. Just as Canadians know first hand, and recognize the variety of different crystalline forms that fall as ice from clouds, we know that the minerals of these volcanic systems form different patterns depending upon their conditions of formation. By examination of these mineral patterns we are able to infer some information about the nature of deep processes that led to eruption.