|
|
|
|
is an
active composite
or stratovolcano with a horseshoe - shaped crater (very
similar to the newly formed crater by the explosion of Mount
Saint Helens
in 1980) with a diameter of 2 km and 600m deep. Its
summit reaches 4787m and its exact geographical
position is
0.171°S and 78.598°W,
which locates it some 10 km west of Quito, Ecuador's capital.
This city of 2 million people lies at the eastern foot of Mount Pichincha,
however the crater is located away
from the city with its opening pointing west towards the
Pacific coast.
Furthermore a range of hills protects the city from any
eventual lava flows. |
|
|
Oct. 7th, 1999: Photo
by Mateo Lutz |
|
The volcanic
activity of Guagua Pichincha expresses itself in the formation of
lava domes on the crater floor (see
photos below). The viscous
magma (more acid, slow moving and thick)
from the earth's interior pushes up through a vent
and builts itself up in those domes with some hundred meters
across. You could also imagine this process like when toothpaste squeezes out of
the tube and sticks around the opening of the top
without flowing too far away as do the more basic basalt
lavas. Those lava domes also have several steam vents, where
hot air and gases continuously escape
(fumaroles). When the pressure from the inside gets too strong, the domes collapse and we
have then larger eruptions
of gases, ashes and lava. Since
its re-activation in 1999 nine such domes built themselves
up and eight self-destruct themselves with the last one
now several years old as the inside pressure declined in
the last few years. Lava which
was ejected in
those events, flew down the breach in the crater wall towards
the coast in a westerly direction
and the fallout of ashes depended on the winds. |
|
|
|
|
A huge historical explosion was recorded by the recently arrived
Spaniards in 1660. They recorded
in their chronicles about 40cm of
ashes in the city (although I would take that with a grain of salt) and pyroclastic flows to the west. Not much is known since then but in
August 1981 the
volcano came alive again after years of dormancy but not much happened
in the following years till the late summer of 1999, when the giant displayed its power again and after smaller phreatic
eruptions, we had a major one, which covered the city with a
gray film of ash on October 5th and then two days later this
beautiful mushroom (see above or click
for a full-blown photo)
could be seen at around 7 am in the morning
against a beautiful blue sky. |
|
|
Oct. 17th,
2002: Photo by the author |
July 11th,
2005: Photo by
the author |
|
The
volcanic activity declined in the last few years as can be
appreciated in those two photos of the lava dome above. In
2002 several fumaroles with a larger
one (called the Locomotora) can be observed whereas in 2005 no
steam could be detected. Also the
smell of sulfur diminished considerably. |
|
|
|
|
The main danger of an big eruption for Quito is the fall of ashes and
mudslides, which may occur in the rainy season. Twice the city was already covered with ashes and the airport
had to close for weeks for cleaning purposes. Fine ashes
entering the jet engines may damage them, so all the ash has to
be removed from the runways. In Quito's case, as there are no
proper cleaning machines, thousand of persons sweep by hand with brooms the
debris of the asphalt. The settlement most affected by a larger eruption would be Mindo,
a small town of a few thousand people, which lies due west of the
volcano, where the crater is breached and so lava flows and lahars would congregate in the Mindo valley as
most rivers, originating from the flanks of the volcano meet there.
Other towns affected, especially by a huge eruption with collapses of
the crater walls or by large accumulations of ashes at the mountain
flanks are Lloa, which is located right at the foot of the
volcano to the south and which for a short time was evacuated and Nono. |
|
|
|
A small sudden shift
in the tectonic plates were probably the cause of
the increased activities and eruptions at almost the same time of
Guagua Pichincha and Tungurahua volcanoes. Why
those two heated up and not other ones is a mystery as still the
whole science of volcanology (?) is very immature and inexact as many
processes of volcanic activity happen in the earth's interior.
It is almost
impossible to get a look at the
processes going on there and often just the end results
can be observed. In Ecuador three volcanoes, Cotopaxi, Pichincha and Tungurahua
are monitored with the help of seismographs,
GPS, etc... and watched closely by the
Geophysical Institute. |
|
|
Geoff Mackley,
an independent filmmaker from New Zealand, interested in
volcanic eruptions and other natural disasters
visited the volcano in March of 2001. |
|
|
|
|
Latest Update: |
Danger alert: yellow
in nearby areas
Activity levels dropped considerably in the last few years.
Visible volcanic activity is reduced to a few fumaroles
and smell of sulfur. |
|
|
|
|
