The ash cloud expands and small pyroclastic flows develop from dense ash both ejected and whirled up by impacts on the upper flanks of the cone. (Photo: Jorge Santos)
More on VolcanoDiscovery:
Introduction to Plate Tectonics
: The Earth's upper, rigid layer is broken into several plates which are in constant motion to one another. Most earthquakes and volcanoes occur as result of these plate boundaries.
Small spherical balls of volcanic ash that form from a wet nucleus falling through a volcanic ash cloud.