The Chemistry of Earth History with Ben Gill

Travis Williams (00:00.238)

Music

Travis

When you think about our prehistoric world, what exactly do you picture? For me, I picture big things. Dinosaurs, volcanoes, continents moving. But I also realized that sometimes the smallest things can't have the largest impacts and provide some of the biggest clues to what our past was really like. Truth be told, I'm not all that sure how this fits together to tell the story of Earth, but thankfully Virginia Tech's Ben Gill was willing to join me to help me gain a better understanding of this topic.

Ben is an associate professor in the Department of Geosciences and is also a faculty affiliate of the Global Change Center. His research focuses on reconstructing past environments and ocean chemistry and their relation to the evolution of life on Earth. So I talked with Ben a little bit about how he sits at this intersection between geology, chemistry, and history. We chatted about what some of the elements that we find in rocks can tell us about our history. We talked about some mass extinction events as well as some of the better times that our planet has seen.

and how the information about the good times is actually something NASA's interested in using when it comes to looking at other planets. Ben also shared how his interest in science fiction is actually one of the things that fuels his fascination with this type of work, and of course makes the connection to NASA all the more exciting. I'm Travis Williams and this is Virginia Tech's Curious Conversations.

Travis

And a lot of the things that I've seen written about you, you are called a biogeochemist. And I was curious, what is a biogeochemist?

Ben

So we're really looking at the links between geology and biology. So like all I say, the cycles of elements on Earth, both on the present planet and then that in the past. And so we're looking at the connections between life. So life, there's things like photosynthesis, which is a chemical reaction that's done by life. That's a direct link between sort of biology and the geo part. So the CO2 that those plants are using comes from a variety of sources, but things like the interior of the earth from volcanoes and the like. So these linkages is where I'm really interested in my research is focused. Yeah. And I also saw that you are, I guess an earth historian was another title. I guess what role does the studying of that look, what are you actually, I guess, studying? What type of data are you looking at and how does that relate to history? How are you piecing that together? That's where a lot of the chemistry comes in. So.

I mentioned both studying these cycles in the past, sorry, the present, but also the past. A lot of what I do is I go to the rock record, so look at cemetery rocks, sediments, rock layers, and those are the pages of the history book. Probably if you're more familiar with fossils, you can go out there, you can look at how life has changed through time, and look at those layers and different fossils in them. But you can also look at a variety of other things, and the chemistry of those rocks can tell you a story as well about what's happened on our planet in the past.

 

Travis

That's really cool because I think a lot of times when we think about looking into looking at rocks and looking at like fossils, we think about these like really big things. But it sounds like you're looking at little, little small things and maybe clues to the big picture from those.

Ben

Yeah, exactly. And you kind of mentioned this, but I'm also kind of curious, like, how do you go about how do you go about doing this this research? So my group, so there's some geochemists that just get rocks or sediments in the mail. But we my group. For the most part, we go out, actually gather them in the field. So we go to places like Alaska or we're going to Newfoundland this summer or out west, a variety of different places, take those rocks back. And then there's a lot, many sets of processing that we want to analyze them for different elements in them or isotopes of elements as well back in the laboratory.

Travis

Is there an advantage to going out and getting your own rocks and being there in field?

Ben

It helps with context. A lot of times we're collaborating with other people that are like studying the physical properties of the rocks or the fossils as well. So being with those people, like just the conversations you have in the field, you, as I said, we're interested in sort of intersection of all these different things. Having specialists in these various different fields together talking is really useful. On top of just, you know where the rocks came from, you know the context behind where they are, or even just the appreciation of how much effort it can take to like take a rock from the side of a mountain in the middle of nowhere in Alaska and get it all the way back here without losing it in the mail or something like that on the way.

Travis

Well, what types of things can bio and geochemistry, what types of things can those tell us about our past?

Ben

Well, I'm off to say that if you look at the periodic table, you've got all those elements on there. Each one of those elements can tell you a story about their past and what's happened. So each one of those elements is a cycle. It could be used by different forms of life or can be put into the, we call it Earth system, but like the surface part of the planet in different ways. So each one of them, we tell you a little bit about what's going on. So we can tell you things like the isotopes of carbon, they'll understand how carbon was cycled. Like when things die, how it's utilized has changed and stuff like that. Because things like we look at sulfur in our lab, which there's a whole sulfur cycle that tells us by microbes and volcanoes and a variety of different things.

 

So each one of those elements we could spend like hours, which I'm sure you don't, hours talking about each one and what they could tell you.

Travis

What do chemical cycles mean? And I know that you recreate them, I think. What does that entail?

Ben

So we can look at like a chemical signature in a rock. So I guess we use carbon, which is kind of more familiar. You're mostly made of carbon. So there's two elements of carbon. And so they primarily are used the same way by different.

Organisms or different chemical reactions that happen on the planet will use them, but the different isotopes of carbon, there's two different types. Carbon -12 is just refers to the mass of the carbon molecule and carbon -13. They're used broadly the same, but just slightly different. And we can discern those differences in usage. So things like a volcano dumping a bunch of CO2 in the atmosphere will have a certain signature carbon isotope signature that you could see. And then things like photosynthesis actually highly discriminate between the two different isotopes. So if you look at the carbon in a rock, you can sort of decipher those things. So some of the first evidence of life on Earth or photosynthesis or life on Earth is like looking at carbon isotope signatures in really, really, really old rocks. It's just one example. But there's different processes like volcanoes going off or how much photosynthesis is happening on the planet or a variety of other processes will leave the signatures in the rock. And then you can look at how...those have changed through time through those rock layers to get a sense of like how the carbon is, what's putting carbon into like the oceans and atmosphere, what's taking it out and the sort of balances between the two.

Travis

So could you potentially look back and say like, hey, there's a lot of carbon in this one period we think, and then like draw a conclusion that there had been a lot of volcanic activity at that time period?

Ben

Absolutely. And that's what's, not to get ahead of ourselves, but at least we've probably talked about that, like during this mass extinction event that I've studied there are signatures in the rock that suggest that along with the fact that we can date, there's volcanoes actually in Virginia, like leftover volcanoes in Virginia that date to the exact same time that you see the signature in the rock that suggests that volcanoes dumped a bunch of CO2 and methane in the atmosphere. And then you actually have the volcanoes that are dated to that exact time. So that's about as good as it gets as a geologist of a dead ringer.

Travis

Yeah. Well, let's, let's talk about that. I was going to ask, cause I know a lot of your work is, studying extinctions. What types of things can we learn by studying extinctions?

Ben

There's a number of things. So one of the common things that people say is that like, so the earth is going through undergoing some change today. That's a lot to do with like the amount of humans on the planet and our population exploding and are using different resources and climate is changing and the environment is changing. So we can look at in the past at maybe not, hopefully not as bad as these mass extinction events that I study, but.

Earth has changed in the past and run the experiment, although the Earth was obviously a different place, somewhat different place at these different times in the past. But the Earth has run the experiment. So you can see, for instance, if there's a volcano splitting a bunch of CO2 in the atmosphere, what happens in the aftermath of that? We've got the whole story laid out after what happens when those things happen. So by studying those events, we can better predict what may happen in the future as our environment and climate changes on the planet. That's one of the more common ones for studying these events.

Travis

And so one of the things that I knew that we've talked about, you and I talked prior to this that you're studying is the mass extinction event from the Triassic period, if I'm saying that correctly. Is that the period, was that the mass extinction event that impacted the dinosaurs?

Ben

This is the one before it. So it did have an impact on the dinosaurs. So they were around on land at the time.

Recently evolved and appeared on the planet, but they weren't very dominant in interest rate because some this extinction activity of it It kills sort of the dominant reptiles that were on the planet On land during that time and allowed basically dinosaurs actually proliferate and become the dinosaurs that we see in the movies and stuff like that or at least The one that we think away think about a dinosaur or what they are Well, I killed the one actually the kills them is at the end of the end of the Cretaceous and that's the asteroid impact.

Travis

Okay, so this one this one actually sounds like it helped the dinosaurs take over.

Ben

Yeah, with these massive seizure events, there's usually like winners and losers. So the archosaurs, which were other reptiles that were on the, it's like the Demetrodon, which you might see like in toy stores with the big fin on its back is one of those. They lose out on the extinction event and the dinosaurs kind of proliferate in there on the space that they leave behind. Okay. And I think you were studying, or at least one of the studies, you're trying to figure out, I believe, like what caused it.

Travis

And so I guess there are some common thoughts as to what caused it and maybe some others. What are you looking into? What are you investigating? What do you think may have caused it?

Ben

So the consensus amongst most scientists is that there's these large volcanic eruptions. And so not just like one volcano going out, but we're talking about areas like you find these up and down the eastern seaboard. There are Redmond Sillas volcanoes in South America and Africa. So they would have been massive on that's kind of the paradigm or like the leading hypothesis that would cause these. People have tossed around asteroid impacts and some other things. Where most of the work is being set, and so we have signature, a bunch of different sort of signatures in the rock record suggests that it was volcanoes and there's volcanoes that line up right on with the dates of when this mass extinction happened. Where most of the work is being done now is trying to understand. So volcano goes off, it puts a bunch of CO2 and methane and other greenhouse gases in the atmosphere then that's, so global warming could be one thing that obviously can kill organisms or stresses them out. But there's a lot of other sort of feedbacks and things that happen in the aftermath of that. And so a lot of the work has been done to try to understand what were the more those other sort of drivers, proximal drivers of what's called proximal drivers extinction were. So you've got the volcano that basically is kind of like lighting the match. And then it's the other things that happen in the aftermath trying to understand the cascade events, what had bigger effects on organisms and what didn't.

Travis

Yeah. And do you have some ideas of what that might be?

Ben

So one of the ones we're looking at, at least for like, I spend a lot of time thinking about what happens in the ocean is looking at sort of what we call de -oxygenation. So most, a lot of organisms, animals in the ocean need oxygen to breathe. And so there's a feedback associated with warming the planet that actually will deplete oxygen in the water. And so we're trying to understand the extent how there's sort of evidence that oxygen levels broadly in the ocean went down. That...we're trying to get as like where and how severe it was and how much it affected the organisms that were living in the ocean during the time.

Travis

Wow. That's fascinating.

How did you get into studying the stuff? Were you a kid that grew up loving dinosaurs? I mean, I feel like people often think that dinosaurs are the entry point into studying stuff like this. But what was your entry point?

Ben

Yeah, definitely. I had a dinosaur phase, but I faded out in elementary school at some point. I didn't really come back to it. I kind of fell into geology, kind of.

One of my best friends growing up his dad was a geologist and he would take us out all the time looking at rocks. And my friend thought it was boring and because for peer pressure, I said it was boring too, but I actually was interested in it. And so I, well, I started, graduated high school and started college, actually enrolled as an engineer for like a semester. And then the geology departments, they, they came, I, I knew one of the faculty members there, like growing up one of his kids from Boy Scouts, it's like, you know, you should kind of like, well,

 

give you a scholarship, you should come take an intro geo class and if you like it, you should stick with it. If not, it's no harm, no foul. And also needing money for school. I'm like, okay, yeah, I'll take, I'll take a thousand dollars to take your intro class. It was a good deal. Um, and so with the sort of like, I was interested already a little bit and then that kind of, that, that sort of entry point and then I'm like, oh yeah, I'm, I'm all about geology.

Travis

Okay. So it was the rocks, not the dinosaurs that drew you to geology.

Ben

Yeah, the fossils are cool too. So I kind of like I got in my dino phase and then I kind of set aside and was interested in other things and then kind of came back to it after a while. What drives you, what motivates you to dig in to ask some of these questions about our like very distant past? I asked myself this question a lot. I'm innately curious about things, but like I'm also like part of me is like really into science fiction. And so like thinking of the planet was a very different place in the past.

Like if we went back in time to like 500 million years ago, it's kind of like going to a different, definitely to a different planet and different like life. Some things might be a little familiar, other things would be very, very different. And so that kind of just base curiosity kind of gets into it. I'm also like a very meticulous, like doing laboratory work and very repetitive tasks is really, it soothes my brain, I guess, is one way. So like the chemistry aspect of like comes in as well. But, better understand our planet. I'm an outdoors sort of person and sort of like seeing, and even seeing how the planet is changing now, I kind of been drawn to understand how the planet changed in the past.

Travis

Well, imagine studying mass extinction events. That could be kind of gloomy. So I'm curious. I'm curious when it comes to what you study and how you hope it's used, what in that area gives you hope?

Ben

As I was reflecting, a lot of my students, almost all my students, not all of them, I'll get to this again, they're studying sort of like, yeah, like the bad times on the planet, like how bad it gets. A project that we got funded through NASA recently to the astrobiology, their exobiology astrobiology program is actually looking at sort of the good times. So there's, there are times obviously when they're mass extinction, where things go bad, but there are times where life is proliferated on the planet. And so this most recent project we're working on around the one I'm going to go to the Newfoundland, Newfoundland, Newfoundland, the summer for is looking at like trying to understand why, how the environment on the planet might have been more permissible to like allow or at least help basically life sort of proliferate way back about a half billion years ago. So there's a time interval called like, so if we went back, if we went back about 600 million years ago, there's probably some animals floating around the ocean, but not that many. But as we move into a period we call the Cambrian period, that's where I see basically they call the Cambrian explosion is proliferation of life. You see all these skeletonized organisms in a busy appear in the ocean over that time interval, they all evolve. And so that time interval, and there's sort of plateaus often, there's a huge jump in diversity in the next period called the Ordovician. We're trying to understand sort of the transition between the two and how the life, the planet, how the environment and the planet may have changed to help usher that on and help life sort of proliferate as well. So that's, I guess, the good times. So it's not always a downer.

Travis

Yeah, and I guess if we can learn a little about the bad stuff to avoid and maybe some of the good stuff that we can maybe help cultivate more of, then maybe we'll be in a better spot.

Ben

Yeah, and NASA is interested in it from the standpoint of like now working in things like powerful telescopes where it can look like the atmosphere, like the composition of the atmospheres of exoplanets and different solar systems, trying to understand sort of the using the Earth's past, the Earth's been a very different planet in the past, looking at sort of like what sort of how the planet was habitable at different times in the past. And that kind of gives us a search matrix for like the chemistry of the atmosphere. If we detect certain elements and certain ratios of elements at different atmospheres, where the planet, those plants might be habitable to life as we know it as well, or life as we existed on our planet in the past.

Travis

Well, I said it does tap into the science fiction interest that you have.

Ben

Yeah, exactly. That's a little more direct line between the two. Yeah.

Travis Williams (17:03.726)

And thanks to Ben for sharing his insights related to geosciences and our Earth's history. If you or someone you know would make for a great curious conversation, email me at traviskw at vt .edu. I'm Travis Williams and this has been Virginia Tech's Curious Conversations.