PubTalk 08/2019 — Pliocene World

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Title: Pliocene World: Earth's Climate 3 Million Years Ago and How it Relates to our Future
By Marci Robinson, USGS Research Geologist 

  • Three million years ago, during the late Pliocene, CO2 levels were similar to today, but global temperatures and sea level were much higher
  • Find out how we use microfossils to reconstruct temperature, salinity and more across the globe from this geological interval just before ice ages began. 
  • Using our reconstruction of the Pliocene world, we better understand the climate dynamics of a warmer world, and global climate models better simulate our future climate. 


Date Taken:

Length: 00:53:50

Location Taken: Menlo Park, CA, US

Video Credits

Amelia Redhill,


 [Please stand by for realtime captions.]
>> Good evening ladies and gentlemen. Would like to welcome you to the public lecture series USGS  and again we had to do this every month and I am John Ballin and I'm a research scientist here for 42 years before retiring three years ago and I am a Michael paleontologist like Marcy and I want to remind you of the talk of September 26 discoveries questions and future research USGS biology and diseases and other things . [Indiscernible - muffled] Dr. Marci Robinson  has a diverse carrier. She actually started as a technician and she rose to be a [Indiscernible] and she went to graduate school and she was raising three sons and she finished her PhD at George Mason University in 2007 and then became a postdoc with USGS  in 2009 and now she's a researcher [Indiscernible - muffled] again she went to [Indiscernible - muffled] in North Carolina and her more recent work has been looking at reconstruction [Indiscernible - muffled] many years ago and she has been recently working on [Indiscernible - muffled] which is 7 million years ago but today she will be talking about the Pliocene  which is almost recently [Indiscernible] period 3 million years ago so Marci's talk is about her work  for the Pliocene reconstruction  about 3 million years ago and is used by paleontologist [Indiscernible - muffled] to better understand how it response to future changes in carbon monoxide and I think Marcy will tell you [Indiscernible - muffled]. The the talk goes is that we will let Marci finish to talk and  there's a microphone in the back if you have any questions. I will turn it over to Marci. 
>>  [Applause] 
>> Thank you everybody and thank you all for coming and I really am excited to talk to you about the Pliocene and the work I've been doing the last several years. I want to thank John  and he introduced me today because he was very involved in the early days of Pliocene research  so he was part of this from the beginning. I will talk about the Pliocene world . I will talk a little bit about 3 million years ago a time when carbon dioxide levels were very similar to today but the global temperature and sea level were much higher so we will talk about why that is and how that compares to today and I will talk about micro fossils because I may Microtel apologist and I think they are very cool so I hope you think they are very cool by the end of my presentation and I will talk about our future somehow this research applies to what we will apply in the future. Let's start by orienting ourselves in time and I will start with the geologic timescale here and you can see that the Pliocene is circled in red and I will  blow that up for you. We will talk about this period the Pliocene between 5.3 and  about 2.6 million years ago and more specifically I will be talking about the age of the Pliocene and I will focus  right at about 3 million years ago. At the end of the Pliocene that's when we started having the ice age so this is  the period before the Ice Age started. 3 million years ago seems like a really long time ago so when you put it into the perspective of the history of the planet, you can see it's really not that long ago so appeared of time I'll talk about it where that red scar is so pretty recent. So recent that the continent is about in the same position that they are today and they look really familiar and that means the circulation was very similar to what it is today. Interesting very important part to me is that the micro fossils I studied most of the species that were alive in the Pliocene owner  still alive today that means I can compare today's species and how they like to live to the Pliocene.  Let me if anyone is interested in the Pliocene , let me talk to you through this slide because it looks kind of scary. This is time along the bottom and the seer is now undergoing back 1 million years, Tomblin years, 3 million years and the top panel is the isotope so what is showing is the different isotopes and oxygen which are trapped in the micro fossils from the ocean floor and with that records is how much ice there is on the planet so I like to incorporate oxygen and they are more available in the ocean so what this is showing you is actually how much ice is on the planet so we use it as a measure for temperature of the planet so this is our moderate level of oxygen this black line and anything that's above here is warmer and anything below is colder so that's like the global temperature. You can see you have to go back 3 million years to get to a period of time where we have a planet that's as warm as it is today. This bottom panel is showing the carbon dioxide and all these different colors are different toxins that measure paly of carbon dioxide and chemicals in summer measuring different carbon and some are actually looking at plant leaves and moss that are on the plant leaves because density. Even though there is a lot of play in these records you can see you have to go back about 3 million years before we get to a time where the carbon dioxide in the atmosphere is to what it is today. This black line here was our modern level in 2011 but I just checked and the average was for 15 so we have gone up that much since 2011. That is why the Pliocene because it is warmer than it is today and the carbon dioxide is about the same  as it is today. So we recognize this about 30 years ago so that when the USGS  project started and I started working at USGS  about four years ago so I was not there but it's the Pliocene research interpretation and mapping in the goal of this project is to reconstruct past conditions  that might give us an idea of what our future looks like. That way we are going to do this is systematic leave document research the temperature and distribution of vegetation on the planet, more recently we have added the distribution of soils and paly geography and what that looks like so that the elevation of the mountains and the symmetry in the ocean and what the ice sheets look like so these are the reconstructions that I will show you today. So everything I will show you has is a product of many different people, over 30 years so this is a good portion of them but I'm not sure everybody is included. These are all the collaborators,  are USGS folks and collaborators from  all around the world. We get together occasionally and have sprints for the Pliocene dinner  and we get together couple of years ago and in the last 25 years Gary has been the PRISM project leader . Let's talk about me for a minute. I'm a geologist and I'm more specifically a Marine micro paleontologist which means I study very small things from the ocean. I work at the USGS  in Western Virginia is about 30 minutes west of Washington DC which is -- and I work  in the geoscience center. This was the first female geologist hired by the USGS when she was  [Indiscernible] and she is responsible for a lot of the USGS maps in the Northeast.  I spend most of my time at the microscope so there's pictures with me on the microscope with my cup of coffee and I study [Indiscernible - muffled]. They are plankton so they surface in the ocean at the top of the water and they are very small they are single cell produce which means they're not plant from animal they are more live animals because they will make their own food, they have to eat and they don't make their own energy to have to eat other foods to make energy. They secrete Coliseum carbonate shells much like what we call [Indiscernible - muffled] which are C cells are created by the animals so they are very small. Each one of these is about the size of a grain of sand so look at them from the microscope and I like to show them this day because it is what they look like to me when I look through my scope microscope. I'm showing you five different species we tell them apart by the way their [Indiscernible] looks. These are easy I think to tell apart. A lot of them are not so easy to tell apart. They lived for about one month at a time and then when they die their shells fall down to the seafloor and they collected most of the ocean sediment in the deep-seated deep-sea is make up her micro fossils. So how do we use these? We know there environmental preferences so we know the temperature they can live in and the salinity the lecture living and what I'm showing you on the left is a graphic of four different species and where they occur mostly. These species for example like the northern part of the northern Atlantic and some species like the southern part where it's warmer. And different species they live in different places and we know that because we have a record of where they all live today. They also live at different depths in the water column. Even though the plankton live in the surface water, the surface water could be 200 meters. And they live in different depths. There's also others that live on the ocean floor and we know a lot about their environmental preferences. If we look back in time at the sea and different species and where they live the specific place we can tell what the ocean was like at that time in the past because we know what they like today. When we are doing these reconstructions we look at a lot of --  we don't just look at five Foraminifera.  We look at different micro fossils so we have two different species appear, and we also have --  and they're all different kinds of Marine micro fossils that live in the ocean surface. We can use those to tell different what the environment was like in the past and we also have organisms down here the ones that live on the ocean bottom and something like a shrimp and then we also use big shelves in the tell us a lot about the range of temperature and sometimes we have crossed on those big shelves and they tell us something to. What this graphic is showing you is between the plankton and the benthic organism and now these fall to the bottom and when they fall to the bottom they line up by age like this so this should be a sediment course part of the's ocean floor with the oldest on the bottom and the youngest on the top and we can create re-create what the environment was like in terms of ocean circulation, whether it was of dwelling and how much were the nutrients and what kind of temperatures and salinity and oxygenation of the water column. We can tell a lot about this. We don't just look at micro fossils, we also do geochemistry of some things. For example in the shell they are made of calcium carbonate but sometimes magnesium items can get in there and place of the calcium and it turns out that they replace the calcium is correlated to temperature so we can do geochemistry on that and get an independent measure of what temperature is and we can also look at biomarkers. Biomarkers are biological organic modules that different organisms create when they are alive in the fall to the bottom and get the positive in the sediment. We can also get an idea of what it was like in the past. Will use all these different methods to re-create the environment. I will talk about temperature first and most because it is what I do but it's also because it's the most complete data set of those I showed you earlier. We have a really nice he developed temperature data set so we have pieces of temperature reconstruction from all of these sites I'm showing you here. I actually have a few more than I'm showing here. Before I give you the results of the temperature data set I want to tell you whether where the samples come from. Most of the samples come from the ocean program or an iteration of that in one now it's the international discovery program which has a number of ships. The ship I show you in the top left is the joint resolution and it's an ocean sediment chlorine ship so you see the big drilling apparatus in the middle. You see the drillers which is on the top right and when the come up on the drill they come up on the catwalk and we cut them in half and here's an example of what they look like cut in half so these are the ocean sediment cut in half. The last time I failed was almost 5 years ago. All of our samples don't come from the DC drilling sediment course. Some of them come from on land. There's still Marine sediment but they are on lands now because there from the time when the sea level was much higher. Sometimes we drill in there is a USGS  drill sea level that we dug into to get the sample and this is me right there collecting big shell and other samples so the big shell looks like this one this is the version you state fossil and it's 3 million years old. They get bigger than that. They are really cool. What else am I showing you? This is a drilling late sediment so this is on a Lake where they set up the tripod and they are drilling through the eyes and the go through the water and they are drilling the ocean to the lake sediment at the bottom and in the bottom that's us drilling into a ancient coral reef in Australia. Those are examples of where it comes from. We bring the samples back to the lab and reprocess them and we try to get rid of all the mud and we are left with the micro fossils. With put them through a freeze dryer which is the thing in the top and that helps to break down if it's hard, they're not solid like a rock, there like a hard plate and it breaks down and then we put them in the water and [Indiscernible] very scientific and then re-washed them to get rid of everything except the micro fossils. What I spend a lot of time doing at my microscope is using a paintbrush and a one inch by three inch slide with grids on it and I take the Michael fossils and I put them by species in the different boxes. One question you might have is how do you know that all the samples you have are the same age? That's a little bit tricky. There's different ways we figure out how to correlate all our samples and how to make sure that the samples are the same age. On the far right -- and that is  an example of how [Indiscernible]. We know through studying the whole world when different species evolve and when they go extinct and we have ages for these events and we make that based on that progress a look at a sample and I see I got these three species I can narrow it down to know that it's within this page of age. That's one way to make sure over on the left side the black and white column, that is a geomagnetic layer that switches every now and then in the North Pole and South Pole and when that happens it happens simultaneously across the planet very good age 2nd get in age by looking at that and lining those up but the best method we have is oxygen isotope stratigraphy. This is that same line I showed you earlier which is the record of ice on the planet and that the global record so wherever you look on the planet that record looks very similar and we can map that up to a composite record which is what this is, a composite record to match all of our records and we can get really specific ages. That's how we line them up to make sure they're all the same age. These are the results from the C search temperature. They are what you would expect, the red is the warmest around the equator and the blue is the coldest up at the high latitude but that's not really what you want to know. What you want to know is how it differs in Pliocene from today and that's what this is  in this is the temperature anomaly maps if you look at the scale along the bottom the 0 is in the white means the temperature are the same in the Pliocene as they are today  and if it read their warmer in the Pliocene than they are today  and this is slightly cooler in the Pliocene than they are today.  What you see as the equator was pretty much like it is today but the higher latitudes were much warmer in the Pliocene.  Warmer globally if you average all the temperature on the whole planet it it was much more [Indiscernible] today but specific at the higher latitudes are much warmer so we have a reduced north-south gradient which means there is a smaller difference between equator and the poll and we that is due to enhance oceanic key transport so the currents are taking more warmer water to the poll. He also see a reduced gradient talking about the specific ocean around the equator and you see the Western Pacific very similar to the temperatures today than in the eastern Pacific and also where have dwellings it is cooler here now. In the Pliocene that  was much more related to today. What this is showing you is what I'm Pliocene and climate dynamics so you  show you is how strong this temperature signal is. We have latitude on the bottom so this is the North Atlantic, this is the equator and this is going higher into latitude so looking at up through here and this is the difference temperature so higher temperature means that it was much warmer in the Pliocene.  In 1992 one of the first PRISM publications was  in science and it showed the gradient which is the black line with the stars on it and it shows exactly what I was talking about how it was the same in the tropics and the equator but it got much warmer. We just now reproduced using this new data high-resolution data across these improved techniques much better each control and with much more knowledge now on how to do this than we had in 1992 because in 1992 we were figuring out this for the first time and we found that it's the same gradient. What that shows us is that not that we were amazing in 1992 but the temperature differences really not that strong. Now let me go through those other data sets I talked about. We have deep ocean temperatures are in the top right it shows you the different locations around the globe where we have bottom water temperature so we use some of those organisms to figure out what the border water temperature was and the red dots means it was more warmer and the blue dots is colder and the size tells you how much warmer or how much colder it was. And there is for my panels along the bottom our cross-sections so if you look at B for example, this is the North Pole and this is the thought South Pole. So this is Iceland -- this is Greenland and here is  the eastern part of the South America and this is an article. That's how that works so there are cross-sections from pole to pole. The black lines on those plots are modern temperatures and we took the sea surface temperature that we already had and you knew bottom water temperature and we extracted the difference to create a deep ocean data set. What we found from doing that was that the North Atlantic deep water was warmer and there was more of it so with Atlantic Deepwater forms up here cold salty water sinking and it was warmer in the Pliocene and there was more of it circulating through and  intermediate water or near Antarctica so it's not bottom water it's intermediate depth was also warmer. So that is the ocean and we also try to re-create conditions on land by looking at different vegetation and how it was the should be did across the continent and in the Pliocene in this work was led by  the University of Cambria and he looked at vegetation records from all of those black sites, the black dots to see how it was different in the Pliocene and he found that  all of the forest shifted North and the tundra up in the northern hemisphere was squeezed up north as well. The forest spread in middle and Eastern Europe and the big deserts were tropicals and woodlands and now have a graphic here helping. The top is temperature estimates based on distribution of vegetation and I found that it's 10 degrees warmer in order latitude than it is today so there's red and orange shades on the top panel. The bottom panel is precipitation. Where it blue it was more red and birds read it was dryer in the Pliocene  so you can see and North Africa for example it was much more red. That panel also looked at lakes and soils showing the snap up here you can see the Lakeside and the S are the soil sites and he also did a distribution of the different kinds of soils and found basically the same thing as the vegetation. It was much warmer and more wet in the Pliocene and the tundra was  restricted to the higher latitude and the grasslands and the savannas and the continental interior of North America and Asia. They also looked at lakes to see the distributions of lakes in the Pliocene so you get  two maps so the top map is the least amount of water and lakes the dryer version and the bottom panel is the layer version of his Lake distribution. You can see that there are some really large lakes during the Pliocene especially  in Africa and Australia and you might notice there is no blue in the Great Lakes and that's because you know that the Great Lakes were a feature of ice ages so they would [Indiscernible]. We did a failure geography reconstruction and this was led by David rally at the University of Chicago and you see the whole part is filled in because those were glacial features that came out through the Pliocene but  this failure geography model is based on model connection and the layer at the top of the surface and underneath that is a very thick layer of partially molten rock like a toothpaste material or consistency and that the man told and we know that the mental [Indiscernible] and we know how the plates move. We have a pretty good idea how that happens and we also understand how glacial isostatic adjustment works so when we had a big glacier or ice sheet on top of the continent it weighs the content down and pushes the mental out into other areas and if you take that ice out, it re-bounces. This failure geography reconstruction is based on those two things. You might Where it is read the elevations higher in words blue elevation is lower and in Greenland and around an article you have a lot of blue so elevation was lower because of the ice has been removed so the ice was really sick. It has not had time to [Indiscernible] because that happened very slowly. Where it's red it's higher today than it was in the Pliocene and one region I want to point out  is Indonesia. Right through here today there is a lot of the Indonesian through flow where warm water comes into the Indian Ocean and there is reason to believe that that was restricted during the Pliocene so there was not  as much warm water coming through. And then there is ice sheet reconstruction and that's a little bit trickier because there is not as many, not as much evidence of ice sheets as there are other things. We do get an idea of the two-dimensional extension of the ice based on debris which is a little rocks dropped from icebergs and from bottom water temperatures we have so we used ice models to help estimate how much ice there was on the planet and give that 3-D estimation of the thickness and we worked with others who are at University. What they found in their eyes model estimation was that the Greenland ice sheet was restricted to the high latitude and you can see it is right here where the Greenland ice sheet is much smaller, only about 25% of what it is today and and are the, Antarctica and the East sheet is smaller. When we look at sea level the ice that is not that results in about 24 meters of sea level rise. Here on the left that red outline is the modern shoreline and the white outline is what it would have been in the Pliocene  24 meter sea level rise and this estimate 24 meters works really well with a lot of the geomorphological evidence we have where sea level was for example in my area of the woods here in Virginia we have a geomorphic feature which is a feature of the shoreline and what it was 3 million years ago and it was about halfway through Virginia and North Carolina and South Carolina like the eastern half would have been underwater and if you're familiar with I-95 it kind of goes up through I-95. This estimate seems to work out pretty well. So what we have talked about so far. Recap of the Pliocene world. We know that it was warmer  globally than it is today and we know that that's mostly because the high latitude were much warmer and we know there's enhanced sea transport up the polar region and there was a reduced gradient in the Pacific ocean. We know that there is some reduced key transport across the Indonesian through flow and that see Porter and the upwelling water was warmer. We also know there is no Great Lakes it was warmer and more wet on land and on of the terrestrial biomes they all shifted northward in the northern hemisphere and the sea level is up 24 meters higher. So what did we actually accomplish? This is an awful lot of work so the one thing we accomplished is that we have reconstructed the planet 3 million years ago through a lot of time and effort and a lot of people and this has never been done before. Nobody else has ever done this for any time period. But we have actually reconstructed a climate that was in equilibrium from that side it was a very stable time in our history so that is unlike what we have now. That carbon dioxide level is rising so fast now that our climate has not been able to catch up with it so what we have now is not a climate equilibrium so that's on the things we learned and one of the most exciting things what we accomplished here is that we have this huge data set of micro fossils and conditions around the planet and a lot of people including myself are studying the biological diversity and in the warmer time period and now we have records of our species have changed during periods of getting warmer and getting colder. And biological sensitivities so how much and how warm can it get how fast before we allow the species to adapt. We have a huge data set that can answer all these questions and this is really pertinent to all the questions we are asking today how will the fisheries adapt to climate change and will they get will they fall apart or will they get better? These are questions we are trying to answer using these data sets. I have not up to this point talked about climate modeling but in fact, climate modeling has evolved about the same time that this project has been in place. We have worked from the beginning closely with climate modelers so one thing that the PRISM project has supplied is boundary conditions to climate  model. What that means is when climate models start to run an experiment or simulation they have to set it up with certain parameters, parameters like where the continents were, where sea level was in were the outlines of the continent was and what the carbon dioxide content was and what the ice sheets look like so we have these data sets that we supply to the climate modelers and these climate experiments are also aimed at understanding the Pliocene so we work together with them . One really exciting thing that we have done is that we know what the climate looks like in the Pliocene because we have  reconstructed what it looks like so when a climate model can try to simulate a past climate and does a really good job of mapping are ground we have much better confidence in the climate model for projecting future climate and the climate modeling community uses our data set to do that. We also use our data set to get validation points for the climate model so when there is a climate model simulation of the Pliocene they use our data  to compare to theirs and if they agree, that's great but if they disagree, we go back to our data and see if there's something we have done wrong or something we can do better and they go back to their model and see if they need to tweak something. Through this iteration of the past 30 years the data set has gotten better in the model has gotten better and also model model comparison and one that's going on for a while is Pliocene  model into comparison project. These are the leading climate models groups in the world and they all run identical simulations using our boundary conditions and they see how will the model agree with each other so every model is constructed a little bit differently, some of them are better at certain things and some of them are better than others so we are using an array of models to try to get a climate sensitivity and the role of C and the reasons for warming and these model model experiments using our boundary conditions were featured in the intergovernmental panel for climate change report in 2014 and the newest iteration, using a better data set and models will be featured in the sixth assessment report in 2021. So to wrap things up I just want to give you some take-home messages. First of all we have reconstructed the planet 3 million years ago and nobody has done that. It's really cool. Remember that modern climate is not in equilibrium so the Pliocene climate we re-create or reconstructed  may be similar to what we would expect if our carbon dioxide levels stopped right now and the climate had time to catch up but we cannot really say what it's going to look like. I have millions of micro fossils and literally millions of micro fossils and there is an enormous potential for also the future studies based on that. My next thing I'm getting things into his big data visualization because I know there's so much trapped in this data set like cannot get out by just looking at data sheets. Our data and models together have really helped us understand climate and what we have done not only has helped our model to improve but we help the model to improve performance and they provided this example of how to re-create a past period of warmth that our people are using now the study other periods of time. With that I will thank you all for listening and thank you very much. 
>> [Applause] 
>> If you have questions, you can get to the microphone. 
>> Thank you. One of the things he put out that shocked me does everybody is talking now about temperature change grading [Indiscernible - low volume] across the country and you said something about [Indiscernible] degrees warmer in the northern hemisphere. That sounds like a lot for the world. 
>> When people talk about that to the re-difference there giving you a global average temperature. That different from when it's about 10 degrees difference. I'm not sure what that would work out to globally but it is not directly comparable. 
>> You mentioned that your estimating the 3 million years ago to the same animal species today. 3 million years ago we didn't have the evolutionary rates but how can we make sure that the eight same animal 3 million years ago [Indiscernible - low volume] 
>> You're right. We do make an assumption based on that. We have no reason to believe that is different. We have gone back and are comparing the distribution of the different species during Pliocene and today and  they came to work out to like the same subtype of environment and we have no reason to believe that they changed but at the same time that is an assumption that we make. 
>> Great talk. [Indiscernible - low volume] 
>> The Pliocene like I mentioned is a  very stable period of time so it had time to equilibrate the climate one of them is 56 million years ago which I also look at but it was a period of time where we had a very rapid temperature and carbon dioxide increase, the most rapid in the last 65 million years but the -- things were really bad.  The Pliocene is not a direct comparison for that because it was  nice and stable. 
>> So naturally [Indiscernible - low volume] to the Western U.S.. [Indiscernible - low volume] 
>> I was not part of that paper but he went through and looked at different evidence for where lakes were and did a reconstruction. I'm sorry, not really -- 
>>  [Indiscernible - low volume] 
>> [Indiscernible - low volume] 
>> Sure. Yes. Right. The danger is increasing so quickly right now that the cycle is messed up because the responses, the feedback loop is messed up, the earth cannot keep up with what we are putting into the atmosphere and it is cyclical. 
>> [Indiscernible - low volume] 
>> Sure there have been times in the geologic time where it was much much higher. 
>> [Indiscernible - low volume] 
>> I agree with that. 
>> [Indiscernible - low volume] 
>> It was a very stable climate for a long period of geological time in fact that it was the last big warm spell when before we went into the ice age, the last point of equilibrium before it got turned but just because it was the same for a long period of geologic time. 
>> Roughly how long? 
>> Well, let's go back to --  must find out exactly. Let's go back to the very beginning. So it has been since pretty stable for at least this long a time. And it started to get unstable here. 
>> [Indiscernible - low volume] 
>> The ice ages here. 
>> The ice age goes up and down and that's where we see a variation [Indiscernible - low volume] 
>> Thank you for great talk. Could you say something about the there is no practical use for this stuff. This is good but -- 
>>  I would have to disagree with this. 
>>[ laughter ] 
>> How many people in the U.S. actually [Indiscernible - low volume]. 
>> I think good basic sciences with funding and two others only four, working on this and not full time so I would disagree that there is no good use for it. One thing we have done is given all the climate models that a lot of people are listening to around the world a good way to test their ability so there testing the accuracy using our data and if they can do that we have more confidence in the future simulation. 
>> This is not the kind of stuff that Congress is [Indiscernible]. 
>> How the ecology changes and that is completely applicable to what's going on in our fisheries, and our coastal zone, because if the fisheries collapse there is no fish so does have application to what's going on economically in the coastal. 
>> [Indiscernible - low volume] 
>> It should be. The coastal zone managers of small towns actually are city of [Indiscernible] for example storm surges, things like that. The Navy cares. 
>> Great talk. Thank you. [Indiscernible - low volume] 
>> During the Pliocene or  [Indiscernible] I don't know anything about --  
>> [Indiscernible - low volume] 
>> I'm not sure about that. It might have been a different part of the country. I have not run across that around 3 million years. 
>> I just want to know is there any information from your study that shows potentially why the Pliocene stability  changed and [Indiscernible]. 
>> That's a really good question there's a lot of people working on this period of time about 2.7 million years ago that's when the ice started growing in the northern hemisphere and a lot of things seem to have changed 2.7 million years ago. I don't think we have a good idea as to why that happened but we have different atmospheric circulation, that's one idea, the Himalayas got to a point where it disrupted the atmosphere. We know we have colder water that starts up dwelling the Indian Ocean. So many things changed around 2.7 million years ago and there's a lot of people looking about. 
>> All right. Number questions? Thank you all for coming. 
>> [Event concluded]