Volcano and Particle Size Measurement

Particle Size Distribution of Volcanic Ashes

The volcanic ash near the crater of Mount Usu in Hokkaido(Japan), the northernmost Island of Japan, comprises particles near the 200 to 300 µm range and near 40 µm. Because there accumulates dry volcanic ash with little adhesive force between particles, with which microparticles mixes in, the porosity of the sedimentary volcanic ash becomes relatively small (i.e. bulk density increases).

On the other hand, the further away from the crater, the fewer particles in the 200 to 300 µm size range there are, and the nature of the microparticles becomes more dominant (i.e. spongier and stickier).

Although samples at any location contain particles of 1 µm or smaller in size, these particles are suspended in air for a long time because of their slow sedimentation velocity and are also sometimes observed at locations several thousands of kilometers away. They are also considered to be influencing Earth's weather.

Furthermore, volcanic ash indicating a particle size distribution similar to that of calcium carbonate and Portland cement is sometimes collected at some other points. This fact indicates the potential of volcanic ash also being used effectively as a resource in architectural materials and ceramic materials, for example.