Aca - Departamento de Física - Universidad Técnica Federico Santa ...

V Encuentro Sud Americano de Colisiones Inelásticas en la Materia
Elemental analysis of the Chaitén volcano ash 2008-2009 eruptions
Shimrit Elimelech, Jorge E. Valdés, P. Vargas
Depto. de Física, Universidad Técnica Federico Santa María, Casilla 110-V, Valparaíso, Chile
Shimrit.elimelech@usm.cl
The Chaitén volcano eruptions in 2008 and 2009
have provided a significant opportunity to study
the typical heavy elemental content and microstructure
of the ash emitted from one of the most
critical volcanoes in Chile. Recent studies of
Chaitén offer insights about the environmental
effects of the 2008 eruption in the water, vegetation
and air. In this study, we offer new insights
about typical properties of the ash such as composition
and microstructure. This information
allows us understanding of the process leading
the eruption phenomena, explaining its effects
and predicting the eruption future consequences.
Microstructure Characterization was done using
scanning electron microscopy (SEM) with
modes of backscattered electrons (BSE) and
secondary electrons (SE). The elements' content
was found using Scanning electron microscopy–
energy dispersive x-ray spectroscopy (SEM-
EDS) and x-ray diffraction (XRD).
First characterization of the first eruption ash
shows that the ash is highly angular with termination
of needles as is clearly shown in figures 1
and 2. This result corresponds to recent observations,
which were done in 2008 [1].
The microstructure of the first eruption ash can
be characterized mostly by fine grain size particles
(d>4um). It has different shapes,
from glass shard like structures to almost spherical
particles.
However, this fine ash microstructure is considered
to be the greatest health hazard since it can
pass into the lungs, leading to respiratory illnesses
[2]. In addition, it can easily cause ash resuspension
over large areas behind the immediate
region of the eruption.
On the other hand, the microstructure of the second
eruption ash, as it is observed in figure 3,
reflects a very violent eruption consisting of
rocks, chunks and pyroclastic flows. This microstructure
contains various types of crystals with
difference in their geometry and size. It can easily
be observed that the grains size is varying
from hundreds to 500um. However, some grains
show a shard like structure, others have porous
and rough surfaces as can be seen in figures 3-5.
These may indicate something about the eruption
mechanism; a morphology consisting of
pores usually indicates the expansion of gas
bubbles during the eruption.
.
Figure 1. Backscattered electron (BSE) SEM micrograph
of the first eruption ash.
100 Valparaíso, Chile