In Our Time - Catastrophism

Episode Date: January 30, 2014

Melvyn Bragg and his guests discuss Catastrophism, the idea that natural disasters have had a significant influence in moulding the Earth's geological features. In 1822 William Buckland, the first reader of Geology at the University of Oxford, published his famous Reliquae Diluvianae, in which he ascribed most of the fossil record to the effects of Noah's flood. Charles Lyell in his Principles of Geology challenged these writings, arguing that geological change was slow and gradual, and that the processes responsible could still be seen at work today - a school of thought known as Uniformitarianism. But in the 1970s the idea that natural catastrophes were a major factor in the Earth's geology was revived and given new respectability by the discovery of evidence of a gigantic asteroid impact 65 million years ago, believed by many to have resulted in the extinction of the dinosaurs.With:Andrew Scott Leverhulme Emeritus Fellow in the Department of Earth Sciences at Royal Holloway, University of LondonJan Zalasiewicz Senior Lecturer in Geology at the University of LeicesterLeucha Veneer Visiting Scholar at the Faculty of Life Sciences at the University of ManchesterProducer: Thomas Morris.

This BBC podcast is supported by ads outside the UK. Thanks for downloading the In Our Time podcast. For more details about In Our Time and for our terms of use, please go to BBC.co.com.uket, forward slash radio 4. I hope you enjoy the program. Hello, 65 million years ago, a massive object from outer space slammed into what is now the Yucatan Peninsula in Mexico.

A five-mile-wide asteroid made a crater 12 miles deep and 180 across, which is still visible today. Many scientists believed this catastrophic event killed three quarters of life on Earth and caused the extinction of the dinosaurs. When the evidence for this impact was first discovered in the early 1980s, it reawakered interest in the theory of geology which had long fallen out of fashion. Catastrophism. Catastrophism is the idea that the Earth's surface has been shaped by a series of drastic events.

The term is particularly associated with the 19th century French geologist George Cuvier, who believed that fossils of extinct creatures, has proved that the world had undergone some major catastrophes in its past. Although his ideas have been long disregarded by scientists, recent discoveries suggest that he may have had a point. With me to discuss catastrophism are Andrew Scott, Libre Hume Emeritus Fellow in the Department of Earth Sciences at Royal Holloway University of London,

Jan Zalachievich, senior lecturer in geology at the University of Leicter, and Lucia Veneer, visiting scholar at the Faculty of Life Sciences at the University of Manchester. Andrew Scott, Catastrophism was an important theory in geology for many years. Before we get into it, in more detail, could you tell us what it is? Okay. William Huell, in 1832, defined the word catastrophism, and he also actually coined the term uniformitarianism. Catastrophism, he said, was the earth had been affected in the past

by sudden, short-lived violent events, and these were possibly worldwide in scope, and it was really to get the idea that maybe one or seven, several global floods had affected the earth, and the last being interpreted by some, at least, as being Noah's flood. So it was very much in terms of trying to give a name, if you like, to a whole series of ideas that the Earth had been affected by a whole series of floods in Earth history. A part of Noah's flood, which he drew on his evidence,

because he had a leaning towards using the Bible as a source of history. What other evidence did he give for that? I think the idea of Huell was to actually really just coin the term to give a way of putting together a whole series of different people's beliefs that the earth had undergone a series of revolutions and a series of major flood events through time. I think at that time he was more a philosopher rather than actually a geologist in the true sense. But he was really trying to contrast that with uniformitarianism. which he said, which was just been sort of more or less proposed from Hutton and then Lyle, in which it was stated that the same laws and processes operated in the past as they did today and at the same rate, in other words, what we often call the present is the key to the past.

So he was trying to contrast those two different viewpoints in coining those terms. Can we go in a little more specifically here? So he thought that the earth's surface, the shape of the earth, was formed basically, if we can be elliptical here, basically by a series of catastrophists, the first of which might have been the idea of the earth shaped rapidly and vigorously in six days

and then knows. That really was the great shaper, and the opposite was the idea that, no, this was a gradualist evolution, and we can come to that a bit later. But I'd just like to define what he meant by catastrophe. Yes, I think that's what he was trying to say, that that's what a whole series of people

had sort of put together those two opposing viewpoints, if you like, and he was trying to contrast them and the philosophy behind them. So it goes back, you know, as we'll hear, to a whole series of people who had been developing those ideas based upon biblical ideas initially and then looking at the geological record and trying to interpret the geological record. But then it was later on with Hatton and Lyle, who said, well, hang on a minute, it's not quite as, you know, people suggest,

in terms of major global catastrophes. But just to nail it a bit more, I'm sorry of it. So he's saying the fact that there are mountains, the fact that there are seas, the fact that these divisions between continents, this great outside, the general shape of the planet came through, not gradualism, but was really marked by it because of catastrophes.

Yes, so that's the idea of what catastrophism is, yes. Okay, Lushu Veneer, the idea of a global catastrophe, as I've said, goes back to Noah's flood. How much attention was paid to such events before the discipline of catastrophe came in? Well, it's, as Andrew has said, Hewell coined the term in 1832. So before that, we've got a long series of ideas from the Renaissance and indeed from the ancient world, which to us look very much like catastrophism, although that wasn't obviously what they were calling it.

Can you give us some taste of those examples? Yes. In the Renaissance, you begin to get people people have been doing natural history so they've been collecting specimens, they've been cataloging them, criticising ancient authorities, but in the Renaissance, people also begin to say, well, what cause these phenomena that we've been describing?

So what causes earthquakes, what causes floods? And people begin to draw on what they've got to hand, which for a historical document is most obviously the Bible. So in 1638, Robert Flood produced something which he called a mosaical geology, so that's drawing on Moses's account in Genesis. But also on the continent ideas are beginning to develop as well. Descartes touches on sort of the formation of the earth, or rather the formation of Earth's really. His is a very speculative idea about how the Earth might might have formed. But that's not really what he's interested in. He touches on that and then

moves on to his more philosophical interests. So probably the place to really start nailing these down is Thomas Burnett's sacred history of the earth in 1681, which drew on some of Descartes's ideas about how the earth formed, but also drew heavily as obviously the word sacred in that title suggests on biblical accounts. Now Burnett was no biblical literalist. he wasn't interpreting Genesis utterly literally. He was seeing it as sort of more an allegorical description. But at the same time, his theory is heavily theological. And it has this progressive teleological idea of the earth going through a series of changes.

So he's drawing heavily on, for example, Noah's Flood, that after Noah's Flood is when mountains form for Burnett. Before that, the world is perfect, and then with Noah's Flood, you get the changes that we see around us now. Mountains, continents, seas. He sees Noah's Flood is happening before there were any human beings on the planet, doesn't he? More or less, I mean, it's... Because Noah's because of Noah who was a human being on the planet. It's a very short time for him between... So the Earth is a paradise for him before the flood.

It's the flood that really causes all the... So he has a short Earth history idea, does he? What sort of history is he talking about? 6,000 years or something? Yeah, he's on that kind of time scale. He's not signing up to any sort of very specific dates, but he's on a biblical time scale, yes. And he's certainly using the biblical as a reliable,

sorry, the Bible as a reliable record, chronologically speaking. So his theory is built on that flood. We keep going back again, again to the world. Is there anything... Oh, just fine. Is there anything else that he brings to bear his evidence from the Bible treated as history? Or does he shore this up with incidents, with events that happened in classical literature? Yes.

Yes. There's a certain amount of shoring it up with events from classical times that probably the most notable would be Pompeii and the eruption of Vesuvius, as recorded by Pliny. But doesn't he, doesn't he mark the fact that, that that was a local event. Yes. But he's talking about the globe, and Pliny is talking about the Bay of Naples.

That's a very key point for him, yes. The volcanic eruption of Vesuvius is obviously a very, relatively speaking, a small event. It's catastrophic locally, obviously, but it's not global. It's not universal. The flood is the key thing

to which we can attribute global phenomena such as mountain chains. You need to look for possibly other kinds of explanations. He's trying to find naturalistic explanations for things like earthquakes and volcanoes, which he realizes do not occur everywhere, whereas evidence of flooding does occur very widely. Obviously, there are things like rivers everywhere. Shorelines are very similar in lots of places.

So he's finding it slightly difficult to. account for what are clearly some global and some local phenomena. He's juggling it with the Bible. But there's this business of... There's this business of uniformitarianism which is creeping up alongside. Does he feel threatened by that at all? Yes.

I mean, that's certainly in the 17th century, so when Burnett is writing 1681, that kind of idea would have been very... strange, very unusual. Most people are sticking within this kind of biblical chronology. And Burnett is, one of Burnett's targets was an author who had suggested that the flood, in fact, was not universal. So Burnett is very much positing a global event for that. But he then in return had criticism that he wasn't sticking closely enough to biblical chronologies. So the debate is around Burnett's work

and the controversy it generates into the 18th century only leads into these uniformitarian ideas again a later coining for that word a little later. One of the first ten things from me about reading about this is this almost like a geological event in itself, the massive change that we see very occasionally in civilizations of thinking out of one sort of thought history content to another. I mean, in this case, the Jewish Christian tradition,

which provide history and causes and everything, to another, the Enlightenment scientist, this is the shift across. It's fascinating to watch that happen because these extraordinary clever men are working on one certainty, as they think, towards another what becomes equal certainty. We're at a bridge point here.

Would you agree with that, Ian? Yes, yes, very much. And there is a change from accepting and it goes back it's not I think just the biblical tradition but also the if you like the legacy of Aristotle and saying this is how the world is

and you take the authority of the great scholars of the past to actually saying well this is what we can see of the world now how can we work out what actually went on and that transition which is kind of late mid-late 18th century going to the 19th century

it's fascinating because you have all manner of of quite different views of the world, coexisting, even being within the same person at times. Let's take this man, the Frenchman Bufant, our sarcotic chap, but we'll leave it with Bufant. What did he bring to this argument? Well, he was one of the first, if you like,

professional scientists, naturalist. You know, he's been... His dates? His dates. He worked almost through the 18th century. He died just before the French Revolution. Luckily, he died in 1788. And he worked, I think he lived to be 80-ish.

So he lived through that sanctuary. And he was very much part of, he became part of the establishment, you know, what then became the Ancien regime. And he worked as a scientist, and he developed, one of the many things he did, he wrote 36 volumes of the Istoire Natural. 36 volumes? Yes, yeah, yeah.

Retirement project for me, I think. about. But what he wrote late in life was the first scientifically based history of the earth, what the geologists would call the first stratigraphy, where he divided earth history up into seven epochs, right from the beginning, from the formation of the earth, to the present, where there are humans. And he based this, not on biblical accounts, but he based it on what he could see on the ground and what he could read about that, other people had seen, and then a lot of, of course, interpolation in between.

Was this considered to be in advance in thinking about this area? It was controversial, I think. It was so some, it clearly was an advance looking up with hindsight. And some of his interpretations are spot on.

You know, I read them as a geologist. Such as. For instance, he recognised there were, he was the first person, I think, to clearly state that extinctions had happened. There were creatures in the past which were no longer alive because they had become extinct. And he did this with ammonites and bellamites things you could see in the rocks,

in the Jurassic Stata, where he lived around Wombard. And he also did the same thing which Cuvier then developed with a mastodon, this creature which shared characteristics of different animals, but which was clearly no longer alive. And this was part of his epochs of past life. And his time scale is interesting, because in a timescale, you know, what is catastrophic, it depends how long history is. He first started thinking that, rather like Hutton, the earth is endless, a rather misty thing, no, no beginning, no end. And then he thought about it, and I said, no, the earth has to have a beginning and end.

And he devised a published time scale of 75,000 years, which at that time time, was enormous. And he took great pains to say to try and help people understand this enormous timescale. you know, think of it as money, he said. And that was in advance. He was nervous about it because it was clearly a non-biblical time scale. So he had to have some very fancy footwork to keep, you know, the Sorbonne, the religious establishment, not too unhappy and yet to take the ideas forward.

But the man most often associated with catastrophism is another Frenchman, Georges Cuvier. What picture did he present? he presented, again, he developed the ideas. Buffon's ideas fairly quickly, I think, became lost because he was part of the ancient regime. And also, Cuvier was a man who had a great believer in his own powers as a scientist.

But Cuvier, again, demonstrated even more clearly that there were creatures in the past which had become extinct, which were no longer around. And he also looked... Why was that so important? I think to say that the world was different then. Ah.

Because if at that time, you know, do you simply have the world as it is, but simply going back in the past for either a biblical length of time or some indefinite length of time or has the world truly changed. Andrew Scott, can you just take that up

about QBA battling with Christianity and science at the same time? It is fascinating, these two bodies of not. It's fascinating to me. I'm sure it's interest to listeners, too. So how is he making that work for him? Yeah, Cuvier is a very interesting character because, in fact, he was a Huguenot. He was a very

determined Protestant in France, and, in fact, a Lutheran. And he took the view that actually Catholics did everything by authority, but Protestants actually could argue. And so he did everything in faith.

And so he said in faith, everything is submitted to argumentation. I didn't get that in first thought everything is. Everything is submitted to argumentation. So you can argue about things. In other words, you need to look for evidence and to argue. But he wished to discover laws by observation. And in some extent, he separated geological observation from his own Christian philosophy

because he was a very devout Christian, and in fact he was president of the French Bible Society and so on. So, I mean, he was very passionate in his religious. believes, but when he was doing his geological observations, he really wanted to separate out the two. So when he made his observations a successive strata with different animals, particularly, he didn't really want to engage in this idea of it being related to a, if you like, a religious timescale. But it was very interesting because his work was originally published in French. It was then translated by Robert Jameson into English.

Unfortunately, Jameson had a very religious viewpoint, and in his editing and his notes, he made it seem as though Cuvier took this idea of these successive events with different organisms as to be biblical in nature and part of various floods and particularly to do with Noah's floods. So Cuvier got very much attached, particularly by Buckland and others, as being catastrophism is actually part of the biblical tradition of looking at a whole series

of events which consumed the earth followed the last one of which was Noah's flood but actually Cuvier himself never said that. So he demonstrated that the successive series of strata which were deposited with different animals and some had gone extinct but he

really wanted to try to separate his own religious viewpoint from if you like his scientific work. Lucian Veneer was that hard for him intellectually to do that or emotionally even and then let's talk about how these ideas wind through with other scholars over the next

century. Was it difficult for him? Did he find it? I don't think he did, no. Why not? There seem to be here two very distinct traditions and in the it's much more noticeable in the

British tradition that geologists have tried to certainly in the 18th and 19th centuries have a sort of a theological theoretical basis. But continental geologists much more often didn't work like that. And so I think for Cuvier, it was actually very important for him in this new regime in France that was less religious, less, it was meant to sort of change everything.

The whole establishment was supposed to change post-revolution, exactly. It was, exactly, it was very easy for him to say, these two things must be kept separate. In terms of my scientific work, the Bible is simply a historical document to be analyzed alongside the historical records of other cultures. He used Indian and Chinese records when he could get hold of them, which I don't think was very often, but he did try. And he was very keen on really just looking at the strata, looking at the fossils in the strata. and he was really the first person to suggest that you could identify strata by the fossils they contained

and that's why it was so important to identify the fossils so carefully. Right now as Andrews indicated when this came when it moved on came to England and the ideas were taken up they were either consciously or unconsciously

they reverted to becoming part of the Christian scholarship tradition. Is that right? Right. There was certainly a tendency towards that, you know, with Jameson's refashioning, you know, of Cuvier. And let's say the early, rather conscious attempts to take geology, the coming observational science and fitting that, you know,

into a religious or a biblical framework as with Buckland's early work. I wanted to move on precisely to William Bucklew. And also to say that this time, time geology, was the word geology applied to this study yet? It was a sort of rare area of study for persons regarded as eccentric in Buckland's case, spectacularly eccentric we're told. And so these, as it were, boffins, bods were roving around on the edges of real scholarship, as it were. I just want to get its place. It's still hovering around the edges. And what did Buckland do that was significant? Well, Buckland, one of the things he did, and

He did many. He was quite a versatile of what we would call today geologist. What did they call it there? Well, the Geological Society of London certainly, you know, goes from, you know, 18, the early mid-19th century.

Whether Buckland called himself a geology, I, yes. He did. He nodding around the table, that he did. We got that cleared up. Okay, so what did he do? He did. Well, one of the things he did,

he looked at the most recent deposits, and if you do any geology at all, you will clearly see that at the surface of the earth there is a deposit which is clearly different from the underlying and more ancient strata. And we know that England, Britain is a paradise for geology because there are so many differences in it, but where did he do his studies?

Where did he put his trowel? Well, southern England a lot, and there's a place called Kirkland Cave that he investigated, which had bones of hyenas and so. like in. And ideas about that switched from these being

the remains of animals swept in by the flood. So we're back to Noah with the hyenas. We're back to Noah. And then Buckland came in and looked more closely. And then over the years he said, no, these animals actually lived in the cave for quite some time. And then...

How did you find that out? Simply by by doing what we'd call geology, the forensic art. You know, the... But where are you? I sort of realized that, but what were the forensic guards in those days? Well, for instance, if you look at the bones

and see whether they're all smashed up or whether they represent a more or as whole skeleton, you can look at the contents of the cave. And he recognised these things, which he called coprolites. His word, fossilised animal droppings. They were there present in the cave as well as the skeletons. So therefore, a good indication that we had a living community,

and not a dead smashed up one brought into the cave. That community was covered by a layer of mud. Now, originally he then said that there came a flood, you know, the deluge to then cover this. But then later in life, he then reworked that, who is part of the great change of that, from one catastrophe, which is a flood, to the other, you know, which is the glacial theory, the idea, the even more science-fiction-like idea to the day of that day, that you didn't have a major flood going across the land, but the land was covered by ice, maybe a mile thick.

Another catastrophe. Another catastrophe, but a different catastrophe. So he's still with catastrophes and is still biblical, this stage? Well, I think through his life, his, he, my reading of it, you know, as a geologist and not as a historian of science, is that he stuck more to what he could develop from the rocks, from the evidence. he kept his faith as many people did, but again, it was a separation into what was later

called the two magisteria. You have, as Andrew said, you have the religious framework, moral philosophy and so on, and then you have the evidence of the rocks. Andrew, back to you, Andrew Scott. So we've given catastrophism quite a good run, but there is this challenge coming up, and we'll use Charles Lyle as the man,

for which we should be, was a great man, these three volumes in the early 1830. sort of set the tone, set the pace for gradualism. Darwin took one of the first of his volumes on the vehicle and he influenced Darwin massively. So you've got Charles Lyle.

Now are we talking here about a different sort of mind? Is he free of Christianity and Christian history? Is he striking out in a different direction? And what is he doing? Yes, I think so. I think he wanted to have a very different viewpoint. If you like, the

religious side didn't come into it as far as he was concerned. He was looking to develop a theory based upon, I suppose, what's known as Vera Corsa, looking at causes you could see today going on. That's Newton's phrase, isn't it? Yes, that's Newton's phrase.

True causes, yeah. So true causes. So if you like, he started his great work in 1830, as you say, volume one of which went away with Darwin on the Beagle. Between 1830 and 1833, he published his principles of geology.

Now, of course, it's interesting because it's in 1832 that Hewle coined the term uniformitarianism. But Lyle, if you like, people talk about Lyle's book as being called the principles of geology, but actually you need to read the rest of the title, which is quite interesting, because it says being an attempt to explain

the former changes of the Earth surface by reference to causes now in operation. So he was saying, well, let's look at the geology, let's look at the rocks and see the processes which are going on today, and let's try to interpret it that way. But what was key was this idea of a long geological time scale, which something which Hutton had been involved in earlier on,

and it was, if you like, Hutton's view of the present as the key to the past was very influential in this. So if you like, he looked at the modern world and the physical process that they were affecting it. He then deduced that they had functioned in the same way in the geological past. But he also presumed that these processes had always operated at the same way and at the same rates as they do today

and I think that was important because if it's at the same rate then you're talking about a long period Roushra Andrews brought up the names of James Hutton the Scottish farmer and geologist scholar can we take it to him and what he added to it because

this is beginning to move quite quickly now isn't it in geological terms? Yes yes I mean Hutton, his first encounter, as it were, with geology was he was a farmer and he realised the importance of soil erosion and the washing away of surface soils in order to sort of re-fertilise almost the ground. And he saw, therefore, that you need some kind of constant effect.

The soil washes away, how is it replaced over a longer period of time? if the topsoil is all being washed away, then you're going to need some kind of uplift to maintain land versus sea and so on. So he's coming from that angle, but also he's in a very different intellectual tradition from a lot of the English geologists, such as Buckland, a little later, of course, Buckland.

So in 1788, Houghton published his, or presented as a paper, in fact, to the Royal Society in Edinburgh and then published his theory of the earth. And that's actually quite an important name for it. He is in this tradition all the way for a century before from Burnett of these huge theories entitled Theory of the Earth. It's kind of a genre that's grown over the last century.

So Hutton is, in literary terms, in that kind of tradition. But he's coming at it from a very different angle. a deist. So he has a belief in a Christian-like creator but he's not in any way signing up to any kind of biblical

He's not a Noah man, isn't he? He's not a Noah man, no. He's not literally interpreting Genesis he probably isn't particularly interested in Revelation at all. What he wants to do is learn about God through his creation. So he wants to do natural theology as opposed

to scriptural theology. So his whole theory then comes out of this, and he posits that if you're going to have this uplift that is constantly regenerating the surface of the earth, then it's got to be an ongoing, cyclical, eternal process. With no beginning, no discernible beginning or discernible end. Yes, that's his famous quote. No vestige of a beginning, no prospect of an end. And that, again, comes out of this deistic theology. a divine creator would not have created an earth that would break.

Can I just come to you at the end of this part of the programme, that uniformitarianism supplanted catastrophism. Was it about this time, can you tell us, is there a turning point? Lyle, is it Lyle who gathers disciples, not least in other fields, not least Darwin, of course, who just come to his point of view and that becomes, that rolls through. And catastrophism drops off as the first stage of the rock But if indeed it was that even.

Well, as a first approximation, then it was probably that. Lyle was very influential. You know, he was clearly a persuasive man. He was, you know, as well connected, you know, in the societies. You know, he was a very good geologist, you know, again, for the day in the terms of... Terrified people, didn't he? Ruskin said the clink, clink, clink, clink of those hammers,

driving him mad up in the legislature. Yes, quite. Disproving everything he believed in. Yeah, and there was probably an actual conservatism, you know, insights which there is even now. If there are two possible explanations for something, you know, given all the degrees of freedom one had an interpretation, then it's usually better to choose a less dramatic one. And the early days of the Georgian society, they were set up to not to publish ideas, but to gather data. You know, so there was a kind of a mindset, I think, which said, let's just, you know, get the evidence first.

And as I understand it, the entrance of Darwin into the intellectual field reinforced and overthrew anything else. Things were gradual. Things took, we now, not 75,000 years, but millions and millions and millions of years. We couldn't count the millions. And the whole process was seen in a completely different way, the way the world had started, the way the world continued. And Lyle was tremendously influential in that because Lyle did fire Darwin and gave Dahl. in a sense seeded the big idea. So let's say catastrophism drops away.

But, Andrew Scott, things begin to change again. I hope I'm right here, if I'm not weak. We'll finish the program now. In the 1960s, when the Alvarez, the biologist, began to think again about catastrophism. Can you tell us about why that neo-catastrophism, as we have to call it now, came back? Yeah, I think we should actually go back into the middle,

late 50s and early 60s. There are several things that happened then, particularly relating to observations of how sediments were formed. Of course, in Lyle's view, everything took a long period of time. These sediments took a long time to accumulate and so forth.

But there was a recognition in the 50s and into the early 60s of a series of rocks which they realized were deposited very fast. They called turbidites. So these were sediments which had accumulated on the shelf of on the sea floor, which suddenly moved and then went down into a deeper basin and formed very

instantaneous, very thick deposits. In some cases, these may only be a few centimetres or metres thick, such as you see them very nicely displayed in the cliffs around Aberystwyth, which many people have seen on their televisions recently. And these layers of rock, each one of those, was deposited in instant in time. But they realise that some of these single layers of of rock, maybe up to 30 or 40 metres thick, deposited an instant. So that was a very great change in people's understanding of how some sedimentary deposits formed. And then the discovery of what they then called tempestites, obviously you realize these are storm deposits. In other words, a single storm event formed a bed. So people were beginning to think, well, hang on,

it's not just a matter of gradual accumulation of sediment, but there may be periods of very rapid deposition. Can I just go to Lushner? I mentioned the massive crater in Mexico. That takes us into the sixes. Andrew, quite rightly, went back 10 or 15 years. Did that have a huge impact on geologists as well as

on the earth? Yes, it surely must have done. I mean, earlier ideas, people had been unwilling earlier to accept notions of extinction at all, and it was fairly gradually that those came in through the 19th century. you know, until really exploration into the late 19th century really established it for certain,

there were still people saying, but no, these animals could still live somewhere on the earth. So it's only when you come into really the later 19th century and then the 20th century that extinctions are generally accepted. You get more and more confirmation of a series of extinction events more than once, clearly. the extinction of the dinosaurs is the one everyone knows, but there's a number of them throughout the geological timescale. And explanations for these will no longer do with, well, the climate changed, and, you know, there was an ice age, so obviously some species die out, some migrate. That's no longer an adequate explanation.

So when people begin to find evidence of other, especially sort of extraterrestrial, if that's not too silly a phrase. A meteorite strike. As soon as you say extraterrestrial, it sounds a bit dramatic. It sounds okay, that's what it was. But exactly. So, you know, so that kind of changing idea is very important. Yeah, and so near-catastafism comes back as a factor in this debate or examination.

And there's the phrase, was it Stephen Gould's phrase, punctuated equilibrium? Yes, yes. again, it's... Does that help us at all? It helps us, if you like, the micro scale of catastrophism. In that if you look at the record, now we face with a whole messiness of trying to take these strata

and all the evidence in them, which for a long time was mainly the fossils, and looking to see how these changed. And if you collect them, what you tend to find is sometimes you find speeches gradually change from one to the other, but more often you see a species

appears seem to stay much the same for its one, two, three, five in lineers, and then disappear, and another one comes in, quite different. So this was then taken, if you like, the logical conclusion, which was Niles, Eldridge and Stephen Gould, said, okay, well, biology works this way. You get species can evolve quickly and then spread around the world and stay more or less as they are

and then become extinct. So that was an alternative, you know, if you like it, the smaller scale to the idea of this smooth, gradual progression. Andrew, can, a figure who was of great importance in the resurgent of catastrophism was the geologist

Derek Eager. Is that I pronounced? I should have checked it. Yes, no, Derek Eager. What was his argument? Well, he wrote a book called the Nature of the Stratographic Record, and he argued several points. One is that... What date do we talk about? We're talking about in 1973. Right, thank you.

So he published that book, which I think is hugely influential, because he then, he made the point that paleontologists can't live by uniformitarianism alone, he said that actually, when you look at Earth history, you're only seeing tiny records. So he had what he called the phenomenon of the gap being more important than the record.

In other words, he's saying, well, actually, when you're looking at a sequence of rocks, you're not seeing the totality of geological time, you're seeing many gaps. But then because he saw this change in interpretation of some sediments, he then said, well, sometimes the sedimentation is very rapid and spasmodic. So he called this the phenomenon of the catastrophic nature

of much of the stratigraphical record. And so he reckoned that even on a small scale catastrophes, not just the large global scale catastrophes, but even smaller scale catastrophes had a major impact on how we see the earth. So he came up with this wonderful quote that he said the history of any one part of the earth, is like the life of a soldier.

It consists of long periods of boredom and short periods of terror. Can we go back briefly, Anne? We didn't quite do justice to the Alvarez's discovery of the impact. Can you briskly do that? Sadly be coming to the end of our earth time. Yeah, well, it was a distinct change, and it did cause an impact in more senses than one because for the first time,

there was clear evidence of a cause for one of the great extinction events, one of the great mass extinction events of the past. You know, the idea of this element, this is already a rare on earth, but common in meteorites, being sprinkled in one thin layer around the earth, at the same level

where the dinosaurs and a number of other creatures became extinct, that was the first time. There was a, you know, the chain was closed, if you like. The idea remains, controversial to an extent, but nonetheless, it marked a change from any number of possible alternatives to here we have concrete evidence. What state is the debate, what's the state of the debate today?

Well, as Jan said, it's still very controversial. And I think that there are a number of phenomena that are sort of leading people to engage. with neocatastrophic positions again and not just mass extinction events, I think the sudden, fairly sudden anyway discovery of not just one, but many super volcanoes across the earth. The growing awareness, both scientifically and publicly,

of anthropogenic climate change is making people think more generally about sudden climatic changes as well. so I think perhaps everything is up for debate once more. Is there a same time that... Sorry, but I think we can... Yes, I think it requires that both, you know,

Lyle was right, and Cuvia was right, and their two end members of a spectrum. I think we're going to end on this, the consensus that the opposites obtain. You said it, Eager said it in that quotation, didn't he, long periods of board, among which he probably meant the gradualism, and a few seconds of terror

by which he obviously meant catastrophe. I think sort of that is where we're at. I think a middle position is probably the right one. Well, listen, that's satisfying. We've gone to the end. We've come to a neat conclusion. Well, thank you very much. Next week we'll be talking about the Phoenicians,

the great traders and sailors and language makers of the ancient world. So thank you very much for listening. Thank you to Lucia Peneer, Andrew Scott, and to Jan Zala Savage. There are many more Radio 4, arts and discussion programs to download for free. Find these on the website at BBC.com.ukuk slash Radio 4.