The 1982 eruption of Mexico's El Chichon volcano sent vast
quantities of ash high into the stratosphere. If a University of New
Mexico scientist is correct, the ash which went up hasn't all come down
yet.
Most scientists assume that volcanic ash falls to earth within a year
or two after an eruption. But Frans J.M. Rietmeijer says that he can
show that tiny particles collected in 1985 by a balloon above Texas had
come out from El Chichon. What's more, he believes that because
volcanic particles are flat and fall more slowly than spherical particles,
thev may remain aloft for a hundred years or more. The balloon was
originally designed to collect particles of meteoric origin. It took
samples of the air at an altitude of 35 kilometres - near the top of El
Chichon's plume of ash. Rietmeijer says the particles that he analysed
chemically match the ash from the volcano.
