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seablogger


Chaitén Update

volcanoes by seablogger

A dry northeast wind has cleared the coastal clouds today, and it is driving thick, vaporous plume right over the webcam. I have not seen explosions or collapses in the time lapse, just strong, continuous emission. With seismicity remaining extremely elevated for months on end, it is hard to avoid thinking that something a lot more dramatic will happen one of these days.

17 Comments

Comment by Bob

Friday, 5 Jun 09 @ 3:14 PM

Do some volcanoes reach a stage where they blow off pressure in less explosive ways, less dramatically? Do they eventually mature and quiet down?

Curious Bob

Comment by seablogger

Friday, 5 Jun 09 @ 3:24 PM

Volcanoes do all sorts of things, depending on the sources and chemistry of their magma. Volcanoes may tap chemically different sources during their lifespans, and their eruptive style changes accordingly. Chaiten is young, and it is a prime candidate for a really serious eruption. The seismicity has built to a new high, so it certainly is not settling down. Of course all volcanoes eventually go extinct.

Comment by Bob

Friday, 5 Jun 09 @ 6:24 PM

I find this subject fascinating, Alan.

“Volcanoes may tap chemically different sources during their lifespans, and their eruptive style changes accordingly.”

“Eruptive style” changing is wonderfully complex, given that none of us could possibly witness the change. Current and future studies will chip away at the mysteries.

“Chaiten is young, and it is a prime candidate for a really serious eruption.”

Young geologically, right? It already sits in a caldera. Do you know the approx time when an explosion caused the caldera? Or, how many times it’s already exploded?

“The seismicity has built to a new high, so it certainly is not settling down.”

This is a new recent high, yes? How far back do the seismicity records go?

It’s certainly a beautiful looking menace, reminiscent of the old tropical island movies. As destructive as it was, in visual terms I found Mt. St. Helen’s a bit of a dud.

“Of course all volcanoes eventually go extinct.”

Yeah, I saw quite a few in Hawaii, but I didn’t trust ‘em.

The hot spots persevere though. What an earth!

Comment by seablogger

Friday, 5 Jun 09 @ 7:11 PM

Bob, the change can be witnessed, and is witnessed, in most eruptions. It is quite common for the magma mix to change during an eruption. The physics are complex. Different components of magma have different crystallizing temperatures, and they differentiate underground. Over the life cycle of a volcano, very different melts may surface. We know this because rock types vary correspondingly over time in volcanic edifices.

Even in Hawaii this can be seen to some extent. Though all Hawaiian volcanoes are basaltic, late stage cinder cones come from remnant melts depleted of high temperature components, and erupt explosively rather than merely flowing forth.

As for Chaiten, pre 2008, a single geological survey found it to be the product of a single explosive eruption about 9,500 years ago, which was followed by the emplacement of a rhyolite dome in the small caldera. All that terrain has been buried or destroyed now. The first eruptions in 2008 were explosive, then dome building began. That is typical for this sort of volcano. After most of the gas is released, the viscous magma squeezes out. It seemed like a typical sequence.

But Chaiten would not stop. The rate of lava extrusion is faster than any observed anywhere. After some lull periods late last year, activity has increased steadily this year. The seismic energy release is greater than any seen at a volcano not undergoing violent explosive eruption. No one knows what this may mean. It is a pattern unlike any ever witnessed elsewhere. It may be the prologue to a much greater eruption, perhaps one greater than any seen in human history.

Comment by suze

Friday, 5 Jun 09 @ 9:49 PM

Since Chaiten has been emitting smoke and ashes for over a year (I think) now – isn’t THAT affecting the atmosphere almost as much as a giant explosion? I bet it doesn’t, but I’d like to hear your answer.

Comment by seablogger

Friday, 5 Jun 09 @ 9:58 PM

Effects are only local. The plume is not playing high. The ash is rained out, and SO2 release is relatively scant from this volcano, which has extreme rhyolytic chemistry.

Comment by Bob

Friday, 5 Jun 09 @ 10:50 PM

“The seismic energy release is greater than any seen at a volcano not undergoing violent explosive eruption. No one knows what this may mean. It is a pattern unlike any ever witnessed elsewhere. It may be the prologue to a much greater eruption, perhaps one greater than any seen in human history.”

Mother Nature keeps us guessing.

Fascinating stuff. Thanks, Alan.

Comment by Bob

Friday, 5 Jun 09 @ 10:54 PM

One more question, please: I’m not sure that I interpreted this correctly.

“…the change can be witnessed, and is witnessed, in most eruptions. It is quite common for the magma mix to change during an eruption.”

Do you mean witnessed in real time or shortly thereafter, or do you mean by geologists later studying rock?

Comment by seablogger

Saturday, 6 Jun 09 @ 6:50 AM

Witnessed in real time. For example, Ol Doinyo Lengai, a unique African volcano that erupts low temperature carbonate lavas, seems to lapse every forty years or so into a violent explosive phase. When this happened in 2008, the chemistry of the ash was found to be quite different from that of the lavas that had recently been emitted.

Comment by Beano

Saturday, 6 Jun 09 @ 9:28 AM

Some nice images this morning. Heavy fumes tinged by the sun rise.

Comment by Bob

Saturday, 6 Jun 09 @ 2:12 PM

Thanks!

Comment by Jim Powell

Sunday, 7 Jun 09 @ 12:32 AM

Hi Alan,

Right now seems to be the calm before the storm at Chaiten so I’d like to tell you about a volcano that I live close to in Billings, Montana. It is about 70 miles WSW of my house. At one point, 80 million years ago, it was maybe as tall as 20,000 feet. The Rocky Mountains were just starting to rise up. The closest mountains would have been 280 miles to the west in western Idaho and 70-90 miles to the east would have been an inland sea. Nothing to the north and to the south you probably had to go into Colorado before running into mountains. It may be the oldest identifiable volcano in the western US. By using Google Earth and going to coordinates 45.5975 N -109.9319 W the shape of the volcano is still clearly visible.

The lava that flowed from this volcano ranged from basaltic andesite to dacite. The geologists that have studied the volcano think that the magma that fed the volcano came from the Farallon plate and originated between 225- 310 km down. I find it odd that the volcano ever came up where it did. Most volcanoes exist with in about 200 miles of the subduction zone. The volcano is called the Sliderock Volcano.

Comment by seablogger

Sunday, 7 Jun 09 @ 7:47 AM

I’ve heard of Sliderock. I had a “Roadside Geology of Montana” years ago, which I used to read while traveling through that country. The “Roadside Geology” series was quite wonderful for someone like me.

Comment by Ross

Wednesday, 10 Jun 09 @ 8:10 AM

There is a new update on Chaiten translated on The Volcanism Blog.
http://volcanism.wordpress.com/category/volcanoes/chaiten/

The report says that there has been an increase in seismicity with tremors up to 4.4 magnitude and an increase in the number of earthquakes of 2.5 or greater. RSAM values have not exceeded 150,000 units which is 20,000 units above last week update.

Comment by seablogger

Wednesday, 10 Jun 09 @ 8:18 AM

It had been holding steady around 130k for a couple of months. This comports with my impression that the active area of the dome has grown, with wider plume base and greater plume height, when the weather permits viewing.

Comment by Ross

Wednesday, 10 Jun 09 @ 2:32 PM

The weather has cleared. The plume is blowing to the West. Winds seem high.

Comment by seablogger

Wednesday, 10 Jun 09 @ 2:52 PM

I’ll go look. It was so grim this morning, I hadn’t checked for changes.

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