When sci-fact beats sci-fi: Echoes of exploding stars' final cries may be trapped in the rings of trees on Earth Astronomers seeking to chart the history of supernovas that once lit up our skies and flooded our planet with radiation ought to take a look at tree rings, it's been suggested. Robert Brakenridge, a geoscientist at the University of Colorado Boulder’s Institute of Arctic and Alpine Research, reckons stars exploding relatively …
Mentioning the sample size is kind of irrelevant, as this technique will only ever be used for past events. A new event will allow us to confirm that there is an increase in Carbon-14, but we wouldn't need to be looking at tree rings to date that event.
So only existing data about past events will be available, so I can't see the sample size getting (much) bigger.
but we wouldn't need to be looking at tree rings to date that event.
True enough, but looking at tree rings shortly after suitably close and bright supernova explosions are seen would be a good thing to do, both to confirm that this is a measurable effect and to get another data point on the C14 / brightness curve.
@Pascal Monett
We find old tree remains e.g. areas once forest that were inundated by sea and found under sea sediments.
Problem with ancient tree samples is knowing age - there's various dating erasures that give an estimate, but accurate tree dating to a given year means stitching together tree ring history over time (using trees with overlapping rings means you get further and further back) - relies on accurately matching up and, sample size is an issue.
According to the wikipedia article on dendrochronology:
"Currently, the maximum span for fully anchored chronology is a little over 11,000 years B.P. "
"For the period back to 12,400 B.P., the radiocarbon dates are calibrated against dendrochronological dates."
(where B.P. refers to the number of years before the 1st of January 1950.)
So there is certainly data back almost that far. As to where it's from, I imagine bog-oaks and other preserved timbers provide a lot of the data.
'So there is certainly data back almost that far. As to where it's from, I imagine bog-oaks and other preserved timbers provide a lot of the data.'
The older radio-carbon dates are calibrated against corals and foraminifera shells; as well as speleothems (limestone deposits formed in caves such as stalagmites) which can also be independently-dated using U-Th -> Pb.
realistically, all dating methods include assumptions. Using tree ring C14 variations to help calibrate the others is only going to make it more accurate, when results from various methods converge in a repeatable manner [once calibrated correctly].
Currently the 'isotopic decay' methods are all subject to various errors, centering around "what is the amount of material at the beginning of the decay chain". Until we have a way of projecting that backwards that is accurately determined based on converging "date determination" results, we'll just have to assume it's all "just a guess".
There is a layer in the rocks, however, at the end of the cretaceous period if I remember correctly (verified, K-T boundary), that is said to mark the period where the meteor that allegedly killed the dinosaurs allegedly formed the gulf of Mexico and caused a multi-year darkening of the skies... so that event is probably in trees as well, fossilized ones at any rate. Apparently there are materials, isotopes, and structures in that layer that coroborate something _LIKE_ a meteor strike happening and causing a world-wide catastrophe.
In any case, corroborating tree ring info in fossil trees might be a cool thing to find. OK 60-something million year old tree fossils, but still... who knows what we might find if we look for it?
Given that humans are systematically destroying forests at a frightening rate and the ice is melting ever quicker there is not going to be any historical data to check, Oh I know, lets shop down a few more trees to count rings and measure C14 levels (I known you can just get a core but is still leaves a hole in the tree so it is more susceptible to disease).
Call me cynical but although this is all good science we are increasingly having more pressing thing to worry about.
No, if we can find 13,000 year old wood in sufficiently good enough condition that may work. We can compare tree rings of a 1000 year old tree you cut down today with a 1000 year old tree that we think was cut down 800 or 900 years old and match the rings and thus have a ring pattern going back 1800 or 1900 years, and so on. Someone else in the his thread says we can currently go back 11,000 years using this method.
If we found a well preserved tree trunk that was alive 13,000 years ago and was still alive 11,000 years ago at the end of our current record that will work. Maybe buried under the mud in the English Channel in Doggerland?
13.000 year old tree rings...
fossils maybe? [it could happen...]
This topic also implies the use of various dating methods that include carbon 14 dating. And using tree rings to catalog the variations in C14 for a given year just might help calibrate this dating method in ways that greatly improves its accuracy by (essentially) data modeling the "chaotic" component and creating 'fingerprints' (of sorts) for a particular group of years.
Also reminds me of that Dr. Who episode where the earth was covered in forest for a day or so...
I wonder if petrified wood has vestiges of the rings left and if this would work with them? It would be the only reason for this theory, as far as I'm concerned, because then you could really get into more interesting past astronomical events. The only problem is whether this carbon is varied in such rock or just smooth throughout the specimen. Also, I don't remember seeing any petrified wood that had visible tree ring bands to find.
I wonder if petrified wood has vestiges of the rings left and if this would work with them?
Yes, and possibly no. Wiki has a nice example-
https://en.wikipedia.org/wiki/Petrified_wood#/media/File:Polished_petrified_wood_cells.jpg
and I have a nice opalised slice, but that doesn't have a lot of clear rings. I think the challenge would be with the mineralisation process, ie mineral rich water depositing minerals to petrify the sample. So it would probably be unclear if the 14C content was from the original cells, or the mineralisation. Samples are carbon dated though, and you could make assumptions around how long the petrification process takes. I think it'd have pretty wide uncertainty ranges though.
This would be a useful technique to go alongside Be-10 anomalies which are associated with supernovae explosions. These are found in deep ocean sediment cores and ice cores. What's really nice about Be-10 is that it has a 1.4 million year half-life which pushes things far beyond C-14 dating.
Yup. There's the usual challenge of sparse datasets in developing chronologies, anchored or not. Especially when trying to cook them from a pinch of MxD, a dash of alkenones, a few slices of ice and a topping of grant applications.. Especially when there might be large uncertainties around accurately interpreting 14C data-
Rapid-increase anomalies in 14C production have been attributed to cosmic rays from exceptionally large solar flares. However, the proximity and ages of these SNe, the probable size and duration of their γ emissions, the predicted effects on 14C, and the agreement with 14C records together support SNe causation.
So being able to correlate with 10Be and/or other isotope species that aren't commonly assosciated with solar flares should help validate long time-series chronologies, or 14C/SNe causation. Problem with 14C is that stuff gets everywhere..
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