Volcanoes are among the most awe-inspiring features of the Earth, and their activity has been attributed to various causes throughout history. The ancient Romans, for instance, believed that Vulcan, the god of fire, controlled volcanoes, while the Polynesians ascribe their action to the goddess Pele.

View a second image of Volcanic Ash

Found predominantly along plate tectonic boundaries, volcanoes erupt in a number of different ways and emit a variety of materials, including magma, gases, and pyroclastic rocks. These rocks are typically referred to by different names depending upon their size. The smallest pyroclastic rocks, which are no larger than sand grains, are called volcanic ash. Larger varieties are known as cinders or volcanic bombs, which may be as great as four feet in diameter.

Volcanic ash is quite different from more familiar types of ash, such as that generated by burning paper or wood. Instead of being soft or fluffy, the pyroclastic material is hard and insoluble in water. Particles of volcanic ash may also be much smaller than other ashes, often exhibiting diameters less than a thousandth of an inch in size. The mineralogical composition of volcanic ash generally depends upon the type of volcano it originates from and whether or not the material it ejects is primarily acidic or basic in nature.

Questions or comments? Send us an email.

© 1998-2022 by Michael W. Davidson and The Florida State University. All Rights Reserved. No images, graphics, scripts, or applets may be reproduced or used in any manner without permission from the copyright holders. Use of this website means you agree to all of the Legal Terms and Conditions set forth by the owners.

This website is maintained by our
Graphics & Web Programming Team
in collaboration with Optical Microscopy at the
National High Magnetic Field Laboratory.

Last modification: Friday, Nov 13, 2015 at 02:19 PM

Access Count Since November 20, 2003: 12302

For more information on microscope manufacturers,
use the buttons below to navigate to their websites: