Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, United States Geological Survey. Tephra: Volcanic Rock and Glass Fragments. Retrieved on 2008-01-23. less than in diameter. The violent nature of volcanic eruptions involving steam results in the magma and solid rock surrounding the vent being torn into particles of clay to sand size. Volcanic ash can lead to breathing problems, malfunctions in machinery, and from more severe eruptions, years of global cooling.
After falling to the ground after the eruption, the ash deposited on the ground becomes known as an ashfall. Some of this ashfall can become cemented together to form a solid rock called tuff. Over geologic time, the ejection of large quantities of ash will produce an ash cone. Significant accumulations of ashfall can lead to the immediate death of most of the local ecosystem, as well the collapse of roofs on man-made structures. Over time, ashfall can lead to the creation of fertile soils.
