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Old 2021-03-23, 00:16   #485
japelprime
 
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Quote:
Originally Posted by Dr Sardonicus View Post
News reports say that the Fagradals Mountain volcano has been dormant for 6000 years.

I tried to track down how that determination was actually made, but without success. Apparently this particular volcano creates lava flows, without much ash.

I was able to imagine some possibilities. One was, by observing how the rock from lava flows has weathered. Another is, if a lava flow happened to have covered living plants, there might be some charcoal that could be carbon-dated. If some of a lava flow had been subject to regular sedimentary deposits, it would be possible to say how long that had been occurring.

There may be radioactive dating methods other than carbon dating that would apply, but 6000 years is pretty recent for the ones I'm familiar with to be accurate.

Anybody here know? Thanks!
Scientists took the lava under the scope and found out that this is the same type of lava found in older period of time when volcano activity was 6000 - 7000 years ago. It is different type than was coming up 800 years ago. News say this lava is from estimated deep of 17 - 20 km . The lava is Olivine Tholeiitic Basalts type from that time and have not erupted here last 7000 year. Probably coming in high speed transfer direct from the core. Also they find more of CO2 gases than usual. That also support the theory of the dept of this lava coming from.

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Old 2021-03-23, 01:28   #486
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Originally Posted by japelprime View Post
Scientists took the lava under the scope and found out that this is the same type of lava found in older period of time when volcano activity was 6000 - 7000 years ago. It is different type than was coming up 800 years ago. News say this lava is from estimated deep of 17 - 20 km . The lava is Olivine Tholeiitic Basalts type from that time and have not erupted here last 7000 year.
Thank you for your quick response.

But how did they determine that it was that long ago? That's what I'm asking. I read that the last eruption on the peninsula was after human settlement, and was a different volcano. So the last eruption of Fagradals Mountain was before that.

Something is saying that the basalt from the last eruption of Fagradals Mountain is 6000 to 7000 years old, and not 3000 years old or 10000 years old. What?
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Old 2021-03-23, 04:39   #487
LaurV
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Anybody here know? Thanks!
Some random guy passed that way when the lava blobs were still hot and inscribed his name and the date on the cool red hot wall.
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Old 2021-03-23, 14:12   #488
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Originally Posted by LaurV View Post
Some random guy passed that way when the lava blobs were still hot and inscribed his name and the date on the cool red hot wall.

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Old 2021-03-23, 15:18   #489
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Originally Posted by LaurV View Post
Some random guy passed that way when the lava blobs were still hot and inscribed his name and the date on the cool red hot wall.
Sounds like what I heard some YECs saying...

EDIT: (update) I did see PΓ‘ll Einarsson, an emeritus Professor of Geophysics, University of Iceland, named as a source in some of the news reports. I'm guessing he told the reporters how long the volcano had been dormant.

The last eruption on the Reykjanes Peninsula was 781 years ago. That's in recorded history. Some of the news reports muffed that, saying that the Fagradals Mountain volcano (the one currently erupting) had erupted 781 years ago.

Further update: Professor Einarsson has kindly informed me that the last lava flows around Fagradals before the current eruption were dated by C14 and "tephrochronology," the dating of ash flows deposited on top of the lava flows. He also sent me a 20-plus page paper from JΓ–KULL No. 58, 2008 which looks to be interesting reading.

Last fiddled with by Dr Sardonicus on 2021-03-25 at 13:05 Reason: As indicated
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Old 2021-03-24, 18:44   #490
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Quote:
Originally Posted by Dr Sardonicus View Post
Thank you for your quick response.

But how did they determine that it was that long ago? That's what I'm asking. I read that the last eruption on the peninsula was after human settlement, and was a different volcano. So the last eruption of Fagradals Mountain was before that.

Something is saying that the basalt from the last eruption of Fagradals Mountain is 6000 to 7000 years old, and not 3000 years old or 10000 years old. What?
It is mostly two parameters. The richness of Magnesium Oxid and Titan in the material. In this case it have the same amount as the old lava. Specially the low quantity of Titan. I suppose it is also matching more to materials in older-history of earth live.
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Old 2021-03-24, 20:01   #491
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But this tells you only The dept of where the material is coming from. How they know the time ? When geologists digs through the earth layers they are counting the years in the different layers finding this ashes in the layers from that periode of time.
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Old 2021-03-25, 11:48   #492
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Quote:
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How they know the time ?
I don't know but can think of several possibilities. Each could be used on either the material in question or material with similar chemistry, in particular with similar isotopic concentrations.

Endogenous methods include measuring the amount of decay products of U and Th since the material was last liquid. Until then the concentrations of each will be independent of the chemical composition of the bulk. Afterwards, the different minerals will (I believe, I don't know) be different in each mineral. That solidification starts the clock ticking. Similarly, magnetism induced by the Earth's magnetic field will be frozen in both direction and intensity at the time of solidification. We have pretty good estimates for where the terrestrial field has been for rather a long time.

Exogenous methods applicable to surface deposits include counting cosmic ray tracks or measuring erosion evidence, whether by rainfall or by abrasion.

There are doubtless other possibilities.
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Old 2021-08-14, 20:11   #493
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https://www.bbc.com/news/world-latin-america-58215631
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Old 2021-08-14, 21:54   #494
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Haiti hit by a 7.2 earthquake. USGS PAGER is RED for this event. Likely loss of life in the 1,000 to 10,000's. Likely economic loss in the 1 gigadollar range.

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Old 2021-08-14, 22:29   #495
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Haiti... Likely loss of life in the 1,000 to 10,000's. Likely economic loss in the 1 gigadollar range.
There is a saying here in Bimshire... "God is a Bajan." This is why we are often unprepared for many of the situations that are unlikely to (but still /might/) happen.

IMO... Empirically, the gods have something against Haiti and its people...

I sincerely ask that people please read up on the history of the tiny country of Haiti.

Unbelievable horrors. The ramifications of what happened only a few hundred years ago are still playing out in this "modern" day and age.

I find the contrast with the Dominican Republic's path fascinating to study. To understand what should never be allowed to ever happen again.

tl;dr: Please consider donating at least some resources you aren't currently using towards this sudden emergency in Haiti.

In situations like this, the serious first responders need "stuff" immediately.

P.S. Later the bigger groups will analyze the situation, and then ask for hundreds of millions. But with their bureaucracy comes the inevitable latency and overhead...[/cynical]
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