Stable Carbon Isotopes & Paleoclimate Proxies | GEO GIRL

[@williamhogancamp7716]

Just wondering. Atmospheric CO2 on earth nearly all came from life. It seems no matter the cause of CO2 (burning fossil fuels, burning saplings, exhaling, fixing cement made from limestone, heated oceans releasing CO2 near the surface, decaying biologic matter) all is going to be fractionated and deficient in C13. There is still the same amount of C13 supposedly, the concentration is just diluted in atmosphere and shallow seas. So what I am asking is why relatively low C13 concentrations in the atmosphere (compared to what?) is taken to be a product of man made endeavors rather than natural etiologies? Don't mistake my intentions here. I am not saying that a large portion of atmospheric CO2 and much of the concentration increase is not man made, I just do not see how the isotope argument supports it. BTW I do truly enjoy GEO Girl, she is a excellent teacher.

[@GEOGIRL]

Thanks for the question! Don't worry, I love when people ask these sorts of things, we scientists must all have a healthy dose of curiosity and skepticism! ;) So first, the C13 is being compared to C12, since you ask compared to what. And the relatively low ratio of C13 to C12 is being compared to that of modern natural processes that relesae CO2. Because natueral processes that release CO2 like oxygen respiration (decaying biological matter), CO2 exchange at the oceans surface, volcanism, etc. do not discriminate between C isotopes, they should have a normal C13 to C12 ratio similar to their global averages (~1.1% & 98.9%), this means that the atmosphere should also have this C isotope composition. However, since photosynthesis (the process that led to the C rich deposits that we burn) DOES discriminate between the isotopes (plants take up C12 over C13), this means that we are adding a very C12 rich component of CO2 to the atmosphere when we oxidize that material (yes, an atmosphere of 98.9% 12 is already C12 rich, but we can tell when the inputs become even 0.0001% higher because of how sensetive isotope geochemistry is). So combined with the C14 dating of the CO2 in the atmophere which tells us that the extra CO2 inputs these days are not modern, we can pretty easily tell that man is the cause of the recent isotopically light C inputs into the atmosphere. I hope that makes a bit more sense! Thanks for the question ;)

[@JoesFirewoodVideos]

Sunday is too far away, time to watch some old content. I ❤️ GEO GIRL

[@GEOGIRL]

Haha you are too amazing! But you won't have to worry about waiting for content soon, I am planning to start posting twice a week during the summer (June-August) on Sundays and Wednesdays! (I have more time during the summers haha) :)

[@JoesFirewoodVideos]

That’s great news! Between both of my channels I post 2 videos & 1 & 2 live-streams per week, it gets tough trying to think of new video ideas so I know how difficult it is.

[@GEOGIRL]

@@JoesFirewoodVideos Wow that's a lot! Good job! Yea, for me the ideas come easy, what's hard is having to do all the research I need to do to be able to speak intelligently about the topic hahaha🤣

[@MOHAMMADSYAHMI-p7d]

thank you for making this video!!! really life saving since i got test tomorrow

[@GEOGIRL]

Best of luck! :D

[@syahmirahim4125]

@@GEOGIRL thank youuu!!!

[@ameedmassri2352]

great value a lot of appreciation for the time spent for making it easier to understand .thank you

[@GEOGIRL]

Thanks for the comment, I am so glad you found it helpful! :)

[@phil3768]

Really enjoy your videos. I know you are trying to keep them as short as possible, but they are really packed with information that is hard to absorb at the speed you present the material. I guess the options would be to present less material in the same time or present the same amount of material at a slower pace and have a longer video. Or we viewers could hit the pause button on every slide to think about what you just said (and maybe click back to hear it again). That's what I try to do, but that makes the video quite a bit longer. Sometimes I click on 1.25 speed to slow it down. It's pretty amazing that you are so comfortable with the material that you can talk about it so quickly (and soooo many topics!), but remember beginners need some time to think about what is being said.

[@marcmarc172]

this was so good and such important information. There are very few videos out right now on this topic

[@ju4184]

Fantastic content !!! Super clear explanations + very informative for a short(ish) video. Thanks for sharing

[@GEOGIRL]

Thanks so much! :D

[@CD-ou1sg]

Thanks for making this video! You've put a load of work into this and it's really impressive, well done! Please can you share the references for the signatures of carbon isotope ratios of fossil fuels? Who was first to publish that finding?

[@robinleow185]

Hi Rachel, regarding using stromatolites for paleo-marine proxies. Where did the oxygen come from for the calcareous fossilized microbial mats? Given Stromatolites = 3.5 Ga and GOE = 2.4 to 2.0 Ga. Also, the carbon in CO2 in the paleo-atmosphere is always attached to the oxygen. Thank you.

[@minamazaheri3898]

Great work! Fantastic images and explanations! Thanks for sharing.

[@GEOGIRL]

Thanks so much! :)

[@phoenix3992]

Well yes I will continue on to watch the Oxygen isotope, Hydrogen isotope, Strontium isotope, Sulfur isotope, and Molybdenum isotope episodes, thank you very much. Oh... strange to find on a Carbon Isotope video, but.... I'm a huge fan of laundry detergent sheets too. No big chunk of plastic. No goopy slime. Same fresh clothes.

[@vivianasirbu317]

What I don't understand is how is carbon 12 different from carbon? In the periodic table is C6 so we have 6 protons, but how many neutrons? And 12C is the isotope with 6p, 6n.

[@GEOGIRL]

You are absolutely correct, C12 is not different than carbon, it is an isotope of carbon. As I mentioned in the video, carbon has a few different isotopes, C 14 (which has 8 neutrons) is the radioactive isotope of carbon which decays over time. C 12 (with 6 neutrons) and C13 (with 7 neutrons) are the stable isotopes of carbon which do not decay over time. Becuase these isotopes do not decay, we can track the ratio of C 13 to C12 in rocks, plants, microbes, pretty much anything containing carbon to what the the stable isotope ratios are in that material. With this information we have seen that plants and other photosynthesizing organisms preferentially take up light C 12 isotopes over heavier C 13 isotopes, so it is still carbon, but they just prefer light over heavy carbon. I hope that makes sense ;)

[@vivianasirbu317]

It makes sense indeed. Somehow I get stuck at the atomic structure and can't get my head around how they differ at the atomic layer. IC and C12 have the same atomic mass, but how is A-Z different here? Does it mean that the nucleus of the atom from the periodic table has 0 neutrons(so the C has 6 protons and 6 electrons) ? Therefore the addition of 6n makes 12C isotope ?

[@GEOGIRL]

@@vivianasirbu317 Oh I see what you mean, so the way the atomic mass or molar mass of each element is calculated is by averaging that of its naturally occurring stable isotopes by their relative abundance on Earth. So for example, carbon's atomic mass on the periodic table is listed as ~12.01 because that is calculated by averaging that of its isotopes. So here's the break down: - Carbon-12 has a mass of ~12.00 atomic mass units (amu) (becuase it has 6 protons and 6 neutrons) and a natural abundance of 98.93%. - Carbon-13 has a mass of approximately 13.00 amu (becuase it has 7 neutrons and 6 protons) and a natural abundance of 1.07%. Therefore, the average molar mass of naturally occuring stable carbon on Earth is equal to carbon-12's mass multiplied by its natural abundance plus carbon 13's mass multiplied by its natural abundance = (12.00 amu * 0.9893) + (13.00 amu * 0.0107), which equals ~12.01 amu Hope that makes more sense ;)

[@barbaradurfee645]

@@GEOGIRLexcellent explanation!❤

[@jjnoguera]

Un interesante viaje por la historia geológica usando el carbono.

[@GEOGIRL]

Yes! Isn't it amazing how just one element can leave so many clues behind! :D

[@kimf.wendel9113]

Dang this is geeky! Great work, and it is clear there's a lot of passion for the content

[@GEOGIRL]

Thanks so much!

[@kimf.wendel9113]

@@GEOGIRL I am the thankful one for having found your cool channel

[@rickkwitkoski1976]

Thank you for this and so many other vids. Very clearly explained. The deniers, however, being totally ignorant of basic science, will just discount this and anything that doesn't fit their narrative. YOU and others like you need more influence.

[@colleeneck2215]

Thank you for making this! Very helpful

[@GEOGIRL]

No problem, I am so glad you found it helpful! :)

[@lichao7611]

Great video. I am a geologist, and also your fans from China.

[@alimamstudying9462]

Fantastic explaining 💗

[@GEOGIRL]

Thank you! I am glad you found it helpful ;D

[@marko8095]

wow great, thanks. I feel more powerful now xD I was trying to understand how we can measure if methane released is biological product or by burning fuels and this helped!

[@GEOGIRL]

So glad you found it helpful! Thanks for the comment ;)

[@krushnavudamala7254]

These really great topics, thanks for the lecture. If possible could make a lecture about Mercury stable isotopes.

[@GEOGIRL]

Oh Mercury stable isotopes is a great idea, thanks! I will work on that for a future video :)

[@krushnavudamala7254]

@@GEOGIRL Thanks for your update

[@mriqirm323]

Great video! Do you know anything about where chemosynthetic organisms source their carbon? would it also be isotopically light?

[@GEOGIRL]

Thanks :) And yep, absolutely! Organisms like methanogens take up CO2 with lighter C preferentially. However, the signature of such organisms is different than that of plants, so we can use these light carbon signatures to see how heavy a role chemotrophs like methanogens played compared phototrophs like plants. I hope that helps :)

[@palindapadmasri6872]

You are doing a great job congratulations...!🙂 If you interests please look how ancient Sri Lankan civilizations use geology in irrigation. If you do not mind, Could you please help me to get some information on case studies in applications of environmental geochemistry?

[@GEOGIRL]

Thanks for the encouragement! And thanks for the suggestion! What a great idea :D Also, what specific topics in environmental geochem are you interested in?

[@w1nst0n22]

Greatly helpful video! I was wondering if they are expected values of carbon isotopes that can be found clustered as databases. What I mean is, for example are there expected values for the whole Mediterranean coast in iron age ? If yes, were can they be found?

[@GEOGIRL]

Thanks for the comment, I'm glad you liked it! Regarding your question, I am not sure what you mean by expected values, all the C isotope values I know of are measured not theoretical.. But yes, there is data from pretty much around the globe on C isotopes from both modern and ancient sediment, so pretty much wherever there is rock or sediment, we've measured the C isotopes. However, finding it all in one coherent database is a bit difficult or impossible. Unfortunately, you need to do quite a bit of digging. I have left a bunch of papers in the description of this video that you can check out, but I am not sure if they'll have the exact data you are looking for. Let me know if you have any more questions ;)

[@w1nst0n22]

@@GEOGIRL thank you so much for responding! What I meant is whether there are specific expected measurements that work as a baseline for different chronological periods. In a sense I’m asking if for example I want to examine in late Iron Age dietary habits through carbon isotopes in the Mediterranean coast is there a base for the values and depending if my results are higher or lower I can make my conclusions? Hope that makes more sense

[@GEOGIRL]

@@w1nst0n22 So I found this article that seems to be exactly what you are looking for: www.jstor.org/stable/23237960 and I would also suggest that if you are interested in reconstructing dietary information from past civilizations, I would also consider looking into Strontium (Sr) stable isotopes as they are known for their diet reconstructing abilities. Unfortunately, baseline values that can tell us whether a certain isotopic value is 'high' or 'low' depends on where your C isotopes came from and what you are looking for. For example, I have studied oxygen stable isotopes, and we always have to know whether our values represent marine water O isotopes or freshwater O isotopes before we can draw a conclusion (say that the value is relatively 'high' or 'low') because in both cases, the standard that we use to correct our values and the reference material we use to compare our values to is different. Now there are many standards out there but which one you use depends on the material you are measuring your isotopes from, so I wouldn't be able to tell you what standard to use. But I would say check out that paper I linked to (or related papers) and see what they use and then use the same thing since I assume you are working with the same material. Hope that helps ;)

[@wolfgangvon4261]

really nice, thank you for such an amazing course

[@GEOGIRL]

You're so welcome! I am glad you have found the videos helpful!

[@wolfgangvon4261]

@@GEOGIRL are you a Prof.of geology?

[@GEOGIRL]

@@wolfgangvon4261 Yes, I am :) Well I am not a full professor, I am only a TA right now, but the professor I work with lets me co-instruct the class with her, so I guess the answer is technically yes. I am currently in grad school for my doctoral degree and after that I hope to become a full time professor/mentor/researcher of geology or many geo-related topics ;D

[@wolfgangvon4261]

@@GEOGIRL wow, do you published your paper? if so, may i read them?

[@GEOGIRL]

@@wolfgangvon4261 Of course! I only have one currently published and available online at: doi.org/10.1130/B35919.1 But I have several others submitted so fingers crossed they get published soon! ;)

[@abdifatahahmed1369]

Thanks for the video, but I would suggest you slow down a little bit, and if you can, use illustrations like pen or drawings etc. to emphasize

[@hihi-bz5ib]

Her pace was very natural and the slides she used to explain gave the main idea, if you’re having a problem with her pacing you can slow it down by adjusting the settings

[@بشيرالصوفي-ج1م]

Is there a big quarrel that turns into a fight or a quarrel?

[@Anuchan]

In spite of my superior dating skills, I failed the class.

[@samuelkeller4745]

Interesting. Do you know can we assign an age to the delta13C data from ice cores and amber?

[@GEOGIRL]

Well wherever there is 13C there is 14C and we can date things using 14C dating because 14C is the radioactive isotope of C meaning it decays over time at a known rate and we can measure how much is left to get an age.

[@samuelkeller4745]

@@GEOGIRL Good point! So there is a limit on how far back delta13C can be used because samples older than, what is it,

[@GEOGIRL]

@@samuelkeller4745 Yep, exactly. The limit to how far back you can use C isotopes to determine age is about 60,000 years I believe. So past that point the only thing you could use to date it is if there are sediment grains in the ice or amber, which does happen. But the only thing you can do with the grain dating is determine the maximum age of the ice not the absolute age because the you know the grain must be older than the ice, but you don't know by how much. And there could be other dating methods for ice or amber that I am forgetting, but this is just off the top of my head. Hope this helps :)

[@degh6543aqkk]

Better explanation of the carbon isotopes than PBS .. you have some great content.. stay active, for all of us college kids.. (you need a better microphone 🎤 though)

[@GEOGIRL]

Thanks so much! I am so glad you found it helpful. Also, I have gotten a better mic since that video, but I still need a better one lol, I am working on it though! ;)

[@nicholasmaude6906]

Given Carbon-14's short half-life (5730 years) its presence in fossil-fuels should be close to non-existent given how old the coal, natural-gas and crude-oil are.

[@duraimaran6509]

can you talk about the positive and negative carbon isotope excursions??

[@GEOGIRL]

Yea, I will probably have more videos about that in the future, but if you want to check out the biogeochemistry part 1, the NOE, and the Early Paleozoic Oxygen history videos I have, those have some good discussion on C isotope excursions in them! :)

[@GEOGIRL]

Oh also, the GOE and snowball earth video also discussions C isotope excursions (the GOE more so than the snowball earth vid though).

[@duraimaran6509]

@@GEOGIRL sure i would love to.. thanks a lot

[@dennis_mihaylov]

thank you very much!

[@KerriEverlasting]

Have you ever failed an assessment? Have you struggled with a certain topic you just couldn't seem to figure out? What did you do?

[@GEOGIRL]

ABSOLUTELY! I have had entire semesters where my school work suffered because I just wasn't sure yet what I wanted to do and during these semesters I'd lose hope and just not care and I did horrible, failed classes, had to redo some, I mean you name it! It wasn't until I really found my calling within geoscience that I got motivated and did really well. I was an athlete as an undergrad we athletes were thankfully blessed with free tutoring services, so anytime I really stuggled with a topic that was really helpful. But overall, any time I was really trying, I did great. It was only the times that I didn't care that I did very poorly and those times I had to step back and really think about what I wanted to do and why I was taking that course and what I wanted to get out of it. Thankfully, once I chose geology as my major my motivations fell into place and I never had many issues after that. :)

[@KerriEverlasting]

@@GEOGIRL don't answer if you are busy! If not, what's your core goal in geology no matter how silly. Like. For me, I'm convinced of 2 things - Gibbs free energy from clay reactions has huge potential for future energy. I don't know any scientists so it's probably stupid 2. I'm sure there must be buckets of gold(or other valuable things) just lying around waiting for me to find. If I could understand just enough about geology I could. So. Anyway. I have to go back to work on Monday so my questions will probably disappear for a while.

[@whatabouttheearth]

With the release of fossil fuels, why would you have a "really low carbon 14 ratios" because it's half like is only 5,700 years? Wouldn't you have absolutely no carbon 14 in the CO2?

[@GEOGIRL]

That's exactly right, our input completely lacks C14 becuase it's old, but remember that our input is not the only input of CO2 to the atmosphere, there are younger C inputs from volcanism and animal respiration (the food (or carbon) we eat is young and therefore has a lot of C14), so our fossil fuel input brings the total C14 ratio way down but will never bring it all the way to zero because there are other inputs. Hope that makes sense ;)

[@whatabouttheearth]

@@GEOGIRL I've been trying to teach myself a bit of biochem (I no know chem whatsoever) and solidly learn how we know through isotopes that the increase of CO2 in the atmosphere is from fossils fuels, but everyone kept saying there is less C14, and for a while I was getting confused and thinking that can't be right because there wouldn't be less, there would be more C13 and C12 because C14 would be depleted from the Carboniferous period fossil fuels. I essentially came to the conclusion that the C14 ratio is less (without the word ratio) overall but not the level of C14, when everyone was saying "there is less C14", but that didn't seem right. So fossil fuels are the only old input with no C14 right? How does the C14 not start to deteriorate before it's inside life? Isn't carbon made from stars and doest it become radio active in the atmosphere? What engages the dying (for lack of a better word)?

[@GEOGIRL]

​@@whatabouttheearth Yes! You are absolutely correct, whenever we talk about isotopes we are always talking in terms of RATIOS (so relative rather than absolute amounts) but sometimes we forget to say that haha ;) Regarding your question: "How does the C14 not start to deteriorate before it's inside life?" The short answer is: it does, but it doesn't matter for dating purposes. I am not a biologist by training so I may be slightly off, but I'm pretty sure that the C14 ratio of the atmosphere and biosphere remains relatively constant because it's continuously being replenished through new inputs of young C (of course, the ratio of C14 to C12/13 is slowly decreasing through geologic time because C14 is decaying, but this decay is negligible compared to that of C14 in life that dies because life that dies is no longer being replenished with new or young C). For example, once CO2 is taken up by a plant, the plant converts it to organic carbon (such as glucose and other carbohydrates). While the plant is living, it is constantly refreshing it's carbon uptake and output keeping it in equilibrium with the C14 to C12 ratio of the atmosphere. Then once it dies, it no longer exchanges carbon with the atmosphere and therefore, that is the moment at which the C14 begins to deplete due to decay into N14. The relative amount of C14 that was in the atmosphere when the organism was living doesn't really matter because all we need to date their organic remains is the amount of parent (C14) and daughter (N14) isotope. Does that make sense?

[@whatabouttheearth]

@@GEOGIRL So if C14 in fossil fuels is depleted, so essentially N14 again, we would see an increase in N14 in fossil fuel emissions? Wouldn't depleted C14 just be N14 then?

[@MohammadAli-sg8bj]

Just a suggestion, The video is very fast, its like you are in a rush to finish the video,

[@GEOGIRL]

Sorry it seems rushed, I think many of my early videos were like that, but I have been trying to keep a better pace in more recent lectures, hopefully it comes off that way! ;)

[@MohammadAli-sg8bj]

@@GEOGIRL how do. You distinguish Between algee and plants with using delta c13 proxy.

[@GEOGIRL]

@@MohammadAli-sg8bj Well I would just look up d13C values for algae and for plants and see how they differ. Then you could measure your sample and see which it is closer to. Hope that helps ;)

[@MohammadAli-sg8bj]

@@GEOGIRL thanks, I was wondering if you have covered grain size as a climate proxy? In any of your videos

[@GEOGIRL]

@@MohammadAli-sg8bj I don't actually talk about grain size as a climate proxy specifically, but I do have a video that goes over grain size and how it can indicate depositional environment: kzbin.info/www/bejne/noXOcopsnq-Mb5Y If you want I can make a grain size climate proxy video, but you are going to have to send me some references because I have not actually heard of this before haha ;) Thanks!

[@toughenupfluffy7294]

Sediments enriched in carbon-12 and depleted in carbon-13 have been found on Mars, by the Curiosity rover.

[@ThrashmIO]

Do you know of Potholer54?

[@GEOGIRL]

No I didn't, but I just looked him up and found his channel! How cool! Thanks for the comment :)

[@ThrashmIO]

@@GEOGIRL He's an OG science communicator on youtube, also ex-geo. He's more on the debunking side of things. Thought you might be interested. Your subtle snarks made me think of him. 😏

[@GEOGIRL]

@@ThrashmIO Yea I saw his video about earth history where he mentioned being a former geoscientist, so cool! And yes, I can tell he is definitely a bit more out there with the debunking than I am, and I love that! I am glad he's willing to say what I am too scared to say haha🤣

[@ThrashmIO]

@@GEOGIRL The reserve is nice. If you frame something as "thing you believe debunked", the people who need information probably won't see it. Just keep up with "this is cool and fascinating" energy.

[@mohsenalshagdari1686]

ف great keep it up

[@GEOGIRL]

Will do, thanks!

[@ivanhunter3907]

It’s great how you can’t regurgitate the stuff you learned÷. That great.. lol

[@jamesmcfarland2636]

The trolls are gonna hate these facts 😂

[@SeanSchaefer]

more like GEO BABE

[@MariaLucambaTetinha]

Olímpio fumelã kunhomola

[@pete0274]

Interesting that you don't cover the nuclear tests. Why? Is documented that nuclear test increased dramatically C14 isotope globally and the half life of C14 is 5,730 years. Start to decrease, apparently after 1963. "At first, in the 1950s only a few tests were done, but as more, and larger tests were done, scientists realized how dangerous this was. This caused the nuclear powers to sign a Nuclear Test Ban Treaty, which went into effect in October 1963." Only USSR tested over 400 atomic bombs during cold war(Tsar Bomba 58 megatons) "Nuclear testing at Bikini Atoll consisted of the detonation of 24 nuclear weapons by the United States between 1946 and 1958 on Bikini Atoll in the Marshall Islands." God knows how many more was tested by US in other parts of the globe. Even after 1963 Treaty other countries tested nuclear bombs for example 6 by Pakistan and 5 by India . Besides nuclear test we have contaminants from nuclear energy incidents and residues Three Mile Island 1979 US, Chernobyl 1986, Fukushima 2011 and many others which was shoved silently under the carpet. Here comes also Strontium Isotopes 89 with half life of 50 years and Strontium 90 with half life of 28 years. You look at the burning fossil and air pockets in the ice and ignore nuclear chaos, well done. High increase of C12 and C13 is increased by agriculture. Plowing alone will release a huge amount C into the atmosphere and will make the soil to lose nutrients slowly growing into desert.