posted on May, 18 2008 @ 01:41 AM
Mod edit: Changed title from "Chaiten Volcano Magma Chamber Identified?" on author's request.
One of the biggest questions today for anyone following volcanoes is how big the Chaiten eruption will be. Nobody knows much about the volcano. What
we do know is that it had been 9,000 years since the last eruption and that it hasn't stopped erupting since it started on May 2nd. There are also
signs that something worse is coming. As I posted in another thread here is what John Seach had to say about the volcano.
Continuous eruptions are occurring at Chaitén volcano in Chile. The airfield at Chaitén town has been covered by ash and water, and is currently not
able to be used. Ash and pumice is floating northwards along the Chile coast. The bay near Chaitén contains run-off from rivers with a milky-green
colour. A large amount of sediment has blocked river channels, and lahars will continue to overflow river edges. Over the past two days there has been
a marked change in seismic activity at the volcano. Earthquake swarms indicate fracturing of the main conduit, and possible ascent of magma towards
the surface. Increasing pressure from magma is creating a potential explosion hazard, and collapse of the dome, generating
The eruption has been big. There is no doubt. I have seen reports online that the first part of the eruption may have ejected as much as 2 km^3 of
material which is nearly twice as big as Mount St. Helens. A second and more explosive phase started about a week later and was bigger than the first
phase. So just guessing it may have ejected 5+ km^3 of material already.
Then I find this quote....
Here is the most disturbing information I’ve yet seen on the eruption of Chaitén Volcano. It comes from a volcano guide’s blog, Volcano Live. He
does not give his source, but I think he qualifies as an expert on the subject.
Following that the page includes a quote from Seach's website which lists five large quakes that preceded the eruption.
4.4 April 30, 2008 at 11:52 PM 17km E
5.3 May 02, 2008 at 01:51 AM 30km NE
4.9 May 02, 2008 at 07:13 AM 13km NW
4.1 May 02, 2008 at 06:13 PM 16km SW
5.0 May 02, 2008 at 10:36 PM 30 km NE
The source above theorizes that the points may mark the outline of the magma chamber. Is that accurate? I don't know. But lets assume for a minute
that it is. I plotted the points to get a visual of what the surface area of the chamber would look like. It would be oblong. From the widest
points it would stretch about 45k and the narrow points about 30km. Give or take a couple km. I calculated the estimate surface area to be about 460
How to figure out the volume of something like that? It won't have the same height from top to bottom all the way around. I imagine it to be like a
hot water bottle filled up. That doesn't really help me much. I wasn't very good in geometry back in the day. So I borrowed a little help from
the USGS website. I noticed that the Yellowstone caldera had roughly the same shape. It was 60km at its longest point and 40km wide. It is
estimated that the chamber is 10km from top to bottom. Figuring the volume of a cube you'd take 60 x 40 x 10 to get 24,000 km^3. Obviously it
isn't a cube. The USGS estimates the chamber to be 15,000 km^3. In this case 62.5% of the cube volume. With the appearance being theoretically
similar I applied that to the Chaiten system. I estimated 45 x 30 x 5. I assumed the smaller chamber wouldn't be as deep so I cut the height in
half. That would give a cube volume of 6750. Taking 62.5% of that would give us a volume of 4,219.
Assuming those large quakes actually mark the outline of the Chaiten magma chamber and assuming it is shaped like the Yellowstone magma chamber and
only has a depth of 5km then the chamber could in theory hold over 4,000 cubic km of magma.
There is no way to know for sure until this is over. But the eruption has been going on for 2 weeks. It is still going strong. The only end in sight
might be a catastrophic explosion and a collapse of the volcano itself which will do god only knows what. We do know that the volcanic system
already has a caldera that is 3km wide. Who knows how much magma has built up in 9,000 years. But based on what Seach has posted things don't look
good. It has gotten interesting enough that the USGS has just sent a team down to study and observe the event.
Sorry for the long winded post.
[edit on 2008/8/1 by Hellmutt]