Lava flows

Abstract

Lavas are flows of coherent magma that are erupted at the Earth’s surface during effusive volcanic activity which is essentially non-explosive, or, for some basaltic lavas, that are fed by lava fire fountains. Lava flows show great variations in size and shape, and in their surface and internal features. In this chapter we describe these variations and discuss the different controls on lava morphology, such as effusion rate, physical properties (particularly viscosity and yield strength) and environmental factors. Many of the differences between lava flows can be treated by initially dividing them into low viscosity (low silica) and high viscosity (high silica) types. The characteristics of the flows are thereafter controlled by the nature of the environment into which they are extruded, or the nature of the environment into which they then flow, or both.