Pyroclastics
 Pyroclastics or tephra
is a general term for all sizes of particles ejected into the air during
volcanic eruptions. Includes particles as tiny as volcanic ash
and as large as bombs and blocks.
The image at left shows a very
close-up view of volcanic ash. Each one of the ash particles
in this image is smaller than a single pixel on your computer screen!
These ash particles are pumice, volcanic glass that is
full of gas bubbles. The bubbles, called vesicles, form
as gas bubbled out from molten rock that spewed out during a huge eruption
of Brokeoff Mountain in Lassen Volcanic National Park.
The chart on the right shows the
names we use to describe different sizes of tephra. Bombs and blocks can
be enormous! Some of the blocks thrown out of the Woods Mountains volcanic
center in Mojave National Preserve are 15 meters across! |
