 Sarah Vanhoef, I'm one of the trustees of the Woodbury Community Library, and we have Mirna Miranda-O'Neal, who is our library director, and I just want to welcome you tonight and thank the folks from ORCA who are a Montpelier Public Television there in the back, and thank the Conservation Commission for working with us to set this up, and I'm going to let Paul Council introduce George tonight. Thanks, Sarah. Great. Well, thanks for breathing the cold and coming out. This is nothing compared to what we were experiencing 13,000 years ago. Good point. Good point. George is a friend that I've known for quite a while. He's a research assistant professor at the Geologic Department in Norwich, and he's a charter member of the Upper Winooski Field Naturalists in Hartfield, and we've been poking around together with some other naturalists down that way for, jeez, I don't know, 25 years now? Oh, more like 30, yes. I've come to recognize George as a real font of knowledge, and we're lucky to have him here tonight to talk about the glaciers and what they left behind, and George has probably dug more holes in Woodbury than all of us here combined, and has a pretty good idea of what's happening under the soil and among the rocks, so we'll let him tell us about how it got to be that way. Thanks a lot, George. Okay. Thank you, Paul. Yeah. So, how's the level sounding? You hear me? Okay. Great. Thank you, folks. I want to make sure you understand this is meant to be an informal talk. If you have a question along the way, just raise your hand. I want to make sure things are understandable to you. I do tend to talk as a scientist a lot, but hopefully we can keep it fun and interesting. Okay. So, before we start with the slides, I want to ask you folks a couple of questions. I'm curious. Let's see. Are most of you from Woodbury, and everybody from Woodbury here? Okay. All right. Moves. Moves. These two guys are interlovers. Okay. We have to have these very close from. The house, that's okay. Is this really okay? It is. If there's a handstop right there on the line. I want another reason, instead it's okay, is a lot of my work has been done making a geologic map of the Woodbury Quadrangle, a photographic map, and callous makes up a large part of that map, but it all connects together. But another question is how many of you have a garden around here, or a garden somewhere? Okay. And how many of you, when you dig a hole in your garden, you'll get a lot of stones around your garden. Well, it might not be true, but you probably live on what's called glacial till, and you'll hear more about that. And how many of you get nice sand or silt or something like that in the natural soil where you have your garden? Okay. Sometimes nobody's hand is up, but that's good. All right. That could be something other than glacial till. It might be glacial lake deposits. In a sense, we'll let these books get settled. You all have already been making observations on what's called surfacial geology. That's the study of the deposits that are on top of the bedrock. So you all have seen some surfacial geology already. Anytime you dig a hole around you. Looks like we've got enough chairs to close. Right. So we'll see all those slides on that first one once we get going. Can we dim some of the lights without making it pitch dark in here? Is there a way? We can work with this if we need to. Is that okay? What works? Okay. If it's too dark, say so and we'll do something else. I don't want much of that. Because my slides will vary. Okay. So we're not going to go through all this stuff here on this slide. This is a slide that shows you the geologic time scale. With the age of the earth at 4.5 billion years at the bottom and the present up at the top. And the only part that we're going to talk about here in this presentation tonight is the very top. The last 1.8 million years or so. Because that's called the quaternary period. And it's subdivided into the Pleistocene, the time of glaciation. And the Holocene, which is the modern time. And the word Anthropocene is being used to describe the most recent time where humans are heavily influencing the course of the earth's history. So we're going to ignore all of this. And that means we're not going to talk about what the bedrock is like in various places. The rock types and all the events that went into plate tectonics in the formation of Vermont. So pretend you're not interested in dinosaurs or marine fossils or the evolution of life on earth or anything like that. Pretend you don't care about that. We don't have time. So just the top. Okay. So I'm going to talk a little bit more about how the glaciation came about. But suffice it to say that 18 to 25,000 years ago, all of the northern parts of the world were heavily influenced by glacial ice. There were huge ice caps over North America, Greenland, Europe, parts of Northern Asia. And the earth was in across Antarctica. The ice was much more extensive than it is now. So there was a very cold time coming to the end of a couple million years worth of cold periods punctuated by warm periods. So the earth was starting to warm up and the ice was melting and starting to leave behind the deposits that we see in Vermont today. We'll talk a little bit more about that in a moment. But sometimes I'm going to show you graphs and I'll try and point out what the different directions mean. And this is a good first one. This is years before the present going from 16,000 years ago, like 14,000 BC to 10,000 years before the present. And this is a graph of global temperature. And when it's down below this line, it's much cooler. And when it's above this line, it's much warmer. And down here we're going from the end of the glacial time when the ice sheets were widespread across the earth. And there was a warming and a little blip of the cooling and a warming and a pretty good cooling. And then it cooled a bunch and then it warmed abruptly in a matter of decades. This is what they keep binding as they dive into it into the beginning of our modern Holocene time. And the glaciers melted like crazy in this time here from 12,000 on through 10,000 years ago. All of Vermont was ice free before we reached the right-hand end of that graph, but parts of northern Quebec still had an ice cap on them. So it's just a measure of how an abrupt climate change occurred on that. So that was a graph that showed one thing plotted on another. Now we've got a map of New England with Connecticut, Rhode Island, Massachusetts. Here's Cape Cod. Here's Long Island down here. Going up into Maine. Here's Vermont, Quebec, border, Quebec. And this shows where the glacial ice was at different times. So between 28,000 and 23,000 years ago, the ice was down at Long Island. Long Island is there because it's built of glacial moraines. Glacial deposits formed out at the limits of where the glaciers got from. It could have been. There would have been a good name for it. However, when it formed, this was not ocean because the waters were all locked up in the ice and the sea level was vastly lower, much lower. Over 100 meters, 140 meters lower than the present day. So change was coming. The climate was warming like I showed you on that graph. There's dramatic warming. And this was even before the dramatic warming. So the ice progressively retreated through Connecticut and Massachusetts and Southern New Hampshire and Vermont. And by the time we got up to us around here, we were right about 14,000 years ago. So that was before that truly big, abrupt warming that basically destroyed most of the rest of the ice that was blanketing North America. What did they think caused that? There's several combined causes. The best explanation comes from a set of changes in the Earth's orbit. And I have a slide where I can talk about that at the end. But how elongate the Earth's orbit is, how much the hole is tilted from the plane of the Earth's orbit and how much it's spinning around like a top. So those three factors go together to explain a lot of this change. So we had glacial ice retreating and leaving evidence, which we'll talk about. And that is a major factor. That ice retreat is a major factor in influencing the sufficient deposits, the sand and gravel and clay and other materials left behind in Woodbury. I wanted to start, I'm sort of going to come from Woodbury and talking about Vermont in general. But here's a topographic map of Woodbury. Here's South Woodbury, Sabin Pond, Greenwood Lake, Group 14 going through here. Here's Hardwick up here. And so you'll see these maps again and again of different forms. This is your basic topographic map with contour lines that give us a good sense of relative elevations. And for years, geologists would work with maps like this, like the USGS topographic maps you might use for hiking, hunting, that sort of thing. And they tell us a lot. It's essential to have some sort of an accurate map in order to do my work to map one site relative to another. Where's the sand? Where's the gravel? Where's the limit to a lake deposit? But increasingly, we're using newer maps these days. And this is a map native from razor topographic data that we have for all of Vermont. And what it shows you beyond showing the lakes in the same way, here's Sabin Pond, Greenwood Lake, Group 14 winded through here, County Road comes up through here. Beyond that, it shows us with huge incredible detail areas that are fairly flat and they're showed as white and areas that are steep and they're showed as dark. You can't see much on this one, but I'll zoom in on another map and you can start to see this incredible detail. Like, okay, here's Sabin Pond. Group 14, I just drove up Group 14 and wound around. I drove over that little flat white area, that's the delta from this brook that comes in here. There's a wet one there. Group 14 going up this way. All of this stuff on the map that's lined up here is ridges of bedrock. And ridges as small as, say, three or four feet high and 10, 20 feet long. I can easily see them on this sort of map. So it gives me incredible information. For one thing, it tells me that Whitbury is a rough place to farming. Every time you see a little dark line on here, it means there's a steep ridge that you'd either have to clamor over or climb over. It's really showing things, you know, the size of this table and upward show up on these maps. So that's one of the tools we use these days when we start to puzzle out the geology. I actually didn't have maps like this available to me in 2015 when we were doing our geologic mapping here. But we had to get along without it. And then here a little further north, here's, I'm sorry, I'm using the official names as opposed to the names that a lot of people use. So I forget, there's Greenwood Lake, there's Valley Lake, and what do we call Valley Lake? Valley Lake, yeah, we get confused. And here's Buck Lake over here. And if you've ever, for example, hiked around Buck Lake at all, this dark line down here, that's those big cliffs there. And this dark line along here, that's those cliffs over on that side. And here's the Cabinet Road. And this is the quarry, where the granite quarry shows up like a sore thumb. So anyway, so it's a powerful tool we have to look at the landscape. Now this, I'm going to move away from this in a second. This is what we get when we make a surfacial geologic map. It's too messy to really go through right now, but I'm going to start to explain what these maps show. So this is the area around Saban Pond and Forest Lake, what's that called? That's Dark Pond? Nelson Pond. Nelson Pond. And number 10 pond. Yeah. And there's Dark Pond. And then we do agree on Greenwood Lake. Is there an old name for that one too? No. Pretty much Greenwood. Way back when it was called Long Pond. West Long Pond. Oh, I didn't know that. Well, anyway, so there they are for orientation. And then these different colors are the different types of surfacial materials that we encountered as we did this mapping. And I'll zoom in on that and I'll show you that on other simpler maps. And all these red arrows are glacial striations that are scratches made in the rocks as the glacial ice passed over them. And it tells us which way the glacial ice was moving. And those are very important. But again, other maps will show it better. For example, this map, I took away all those, most of the colors. And you can still see glacial ice moving from sort of north to south or sometimes from northwest to southeast. And we'll talk about that in a minute. Then there's this area out on the blue with a kind of a greenish hint to it. These are glacial lake deposits. And we'll definitely talk more about that. And then down through here, there's a set of purple lines, short purple lines from Dog Pond down through Saban. Yeah, Saban. These purple lines are escar deposits, ESKER. Those are glacial stream deposits. We'll get back to that, but they tell us the way the meltwater was flowing near the edge of the ice as it was melting away about 14,000 years ago. So these different things I'm showing on the maps are clues to the glacial history. Can you tell which direction the ice is traveling when you see that on the map? I don't have a photo that'll show that perfectly. No, actually I do have. I'll get to that in just a moment. I think a couple slides along. So now I put the colors on and left out most of the other stuff. This kind of, whatever you call that color, yellowish, mustard, whatever that color. This dominant color on the map is glacial till. So that's this mix of gravel and sand and boulders that underlies most of Woodbury, most of central Vermont, most of Vermont overall is glacial till or bedrock. And there's bedrock scattered all through here. We're not even trying to show it on a map like this. And then these purple deposits are what are called ice contact deposits. Sand and gravel that was deposited basically right up against the glacial ice without being moved much. And then there's some blue things that aren't lakes in here that are glacial lake deposits. And those are anything from sands to silts and clays formed in lakes that temporarily filled our valleys. So we'll get back to that too. And here's a close up around Sabin Pond. I had to change the coding but this red line is the upper limit of what we know about where the glacial lake came to. There's a little hint of it up here but basically we have the escar, the glacial stream deposits coming down into Sabin Pond and getting in a wider zone of sand and gravel deposited adjacent to the ice. This was formed as the glacial ice margin was right about here retreating into here. So these deposits record the last days of the ice. And this blue is an arm of the big glacial lake that filled the Winooski Valley in its tributaries. I'll talk more about that. Moving towards the striations that you mentioned. But first, here's another way we take the data and look at it. Now I've made a slice through the landscape. I'll try not to stand in front of you too much. I kind of like to point at it rather than use the mouse. This dark black line is the land surface. And that's what your topography looks like. It's actually quite exaggerated. So it's probably a couple miles across from the left to the right. And it's only a few hundred feet. The land surface only goes from maybe 900 feet to 1400 feet above sea level. So 500 feet in elevation. So if I don't put any exaggeration on the land, it basically looks like just a little dip and I can't show you the different surficial deposits. But underneath SAVEN pond, based on water wells and other observations, we think there's pretty thick deposits on the order of as much as 100 feet thick in places, but then rapidly thinning to the sides. In most of our hills across Vermont, you can't even show the thickness of the glacial till because it's probably 10 feet or less. Anywhere where you can actually see a ledge sticking up, there isn't any surficial. So I think this is the last of the surficial geologies. Yeah, what I did is I wanted to show you these escar deposits, these glacial stream deposits are seen in several places from Valley Lake and they're gone down all the way to SAVEN ponds sporadically. So this is an example of some glacial striations. These are scratches in the rock. And many times we can see the rock has been scratched, but it's also been shaped. In this case here, this is a big ledge of bedrock in here. To the ice, that's the north side, this is the south side. It's very gentle on the north side and it's very steep and abrupt on the south side. You can't even tell how abrupt, it just drops right off there. And the glacial ice moved from north to south, plucking away at the south side as it went. What happens is the pressure of the ice is really high at the north side and as it passes over the rock and moves past, the pressure is a lot lower. And there's water at the bottom of the glacial ice. The glacier is flowing on a bed of water under great pressure. And under pressure it stays liquid, but when it reaches a zone of low pressure, like down here, it freezes and it cracks the rock apart. And then it gets torn away. And we see these formations called Roche-Moutonais all over the state. And if you look at Camelshump, it has a steep south face and a very gentle north face. It's basically a very large scale version of one of these, indicating the overall direction of motion. And there's some fine scale features that we can see how quartz veins and other things get abraded or not. There's several other ways we can tell the direction of ice motion. That's part of the reason we look at them so closely. And this crazy map, all those red arrows are places where we have data on how the glacial ice moved. And this goes all the way from Bradford to St. John's Ferry to Hardwick. This is your quadrangle. There's Woodbury Mountain. Saban Pond. And the Wunewski River Valley, Waterbury, Montpelier, Berry, Northfield. No, sorry, Northfield, Watesfield. And we've got thousands of glacial ice measurements. And they show various patterns that mean various things. Most of the glacial ice for most of the Pleistocene was moving from the northwest to the southeast, carrying ice out of Canada, out of Quebec, down through our region. If you go other ways, it sweeps around in a different fashion. There's another slide coming up that shows the big picture. I'm not sure what happened to that. And then as the ice was really wasting away, because the climate was warming, the ice was getting thinner, it was still being pushed down from Canada for a long time because it was still cold up there. Snow fell in Canada every year, accumulated, got thicker and thicker, pushed outward, and made this ice keep moving down here in Vermont. But it was thinner, and it was more and more controlled by where the valleys were, so that we had late stages of ice that was streaming down through the Winooski Valley and getting turned by the north-south grain of a lot of our valleys. So the ice started moving more into the Woodbury area, more from north to south, just right down the Kingsbury Bridge, as opposed to heading over George Bradford quite so much or a barge under some ground. So there already were hills and valleys. It wasn't that the glaciers shaped all of those. They partially shaped, but it was already shaped there. Yeah, yeah. When you look at the big topography of Vermont before three million years ago, before the climate had even started to cool very much from the warm times in the earlier years, you would recognize the shape of Vermont. The hills and valleys were roughly where they were. The glaciers definitely shaped our landscape, but when you think what streams did over the previous, oh, just the previous 50 million years before the glaciers came along, the streams working on the landscape are what really shaped it. And then the glaciers are kind of polishing and sandpapering. But the streams operate over such a longer time period that they're what give us the main shape of everything. Not that the Lake Willoughby notch wasn't scoured out by glacier ice coming through it, things like that. Where the Green Mountains were and all, that goes back along before. That's a really good point. So this is glacial tilt. It's a typical example. That's an excavation. It's a sandy gravel pit over in Groton State Forest. I'm looking at the material there. It's sandy material by the mix of stones of every size up to boulders, I don't know. Many times, they're as big as this room or larger, but certainly full of a wide range of grain sizes. And that material is directly the result of melting of glacial ice that had stopped moving and the climate was too warm that the ice stopped moving and it melted in place. And when you melt a half a mile of ice or whatever at the thickest, it was a mile thick and more in places. It melted a half a mile of ice and some of it's going to flow off, but some of it just sort of, the material just settles down in place and then you get this sort of unsorted material like that. It doesn't have lots and lots of big layers of all the boulders in one layer, all the cobbles in another. There are other settings where we get those layers. Here's some over in West Topson area. Again, there's pebbles and very fine sand all mixed together. That's a characteristic of glacial till deposits, not river deposits or lake deposits. That's about a 25 foot high exposure stream bank landslide on Great Brook and Plainfield. Have any of you driven up the Brook Road in Plainfield? Yeah, there's landslides all along there. The reasons are there's a whole other talk on why there are landslides on Great Brook and what their characteristics are, but they're among the most dramatic in the state. And this glacial till is sometimes so sandy, the ones I showed you before, you can reach your fingers in and sort of pull some out easily. This stuff has a lot of silt in it and it's very dense. And these chunks here are not boulders. They're pieces of the till that had broken off in the May 2011 flood and some of them were swept downstream quite a ways and not destroyed. They're rounded up a bit, made into boulders by being rolled along by the stream. These are real boulders. These are rocks, hard stuff. You could hit with a hammer and they'd still be, that's basically a gravel bar. But this glacial till is so strong in some places, so hard that even in stream it doesn't break down right away. And here's an excavation over at Susan and Dave Sawyer's. They were putting in a foundation for their son's place. And that's typical glacial till. It's silty, sandy material with a wide range of cobbles or pebbles, cobbles, boulders in there. And then of course our landscape is studded with boulders. 5, 10, 15, 20 feet across. Name the size and I can find you one. And we've got plenty in Woodbury. It's just my boulder pictures happen to not be from Woodbury. But that one is in the town of Woodbury, I think. It's over on the west side of East Long Pond, so I think you get that one. Dramatically large pieces of granite plucked off with ropes and up to the north, probably, would be my guess. And now we're back to these escurs. They're really crazy features. Sometimes it's very hard to photograph. Like the Woodbury ones, I don't really have a good photo just because they're in the woods and it's always kind of tight. But it's basically in a long gate, serpentine, ridge of sand and gravel. Either they're often 10 to 20 feet or more high and they can be thousands of feet long in places. There's ones up in northern Quebec that go for miles, any of them, miles and miles. The ones around here tend to stop and start. Yeah, I wanted to get back to this map to remind you where they are. We found a line of them. Didn't find any up at Grainwood Lake, and we missed things. There could be a piece up in here. And all the way down as far as Sape and Pond, we found discontinuous pieces of ridges, a sanding gravel ridge. In some places it's been pretty mined out for sanding gravel because it was a good source. There's really nothing there to see sometimes, except maybe on old maps. And this tells us that... I may have another map that comes along, but this will do. This tells us that when these ridges form, they only form under the glacial ice. What happens is there's a stream flowing under the ice, making up a cavity. It's flowing water. It's getting concentrated in from the sides. The ice margin was down here at the southern end of Sape and Pond. And this water was pouring out of the glacial system. There were probably other ones off to the west and east, taking the water, melting out under the ice and bringing out into glacial Lake Manuski. Let's see this more in a couple of slides. Has anyone ever seen one of these ridges before? Does it sound familiar? Absolutely. And where did you see them? You can just call out. Southwood Bird? Southwood, yeah. Massachusetts. Oh, yeah. There's lots going on through Massachusetts. There's a big one around Lindenville. Oh, yes. Yeah, the Posamsik Valley, Barnett, St. Johnsbury, Lindenville. That's one of the most dramatic escrow systems in the state. Yeah, yeah. So this is something we're starting to put together. In the next year, we're trying to summarize all of this information for central Vermont from St. Johnsbury over to Richmond in one big map. And it's quite exciting. And among other things, there'll be a map of all the escrow systems put together. Not just one little piece. And there's a little gap in Sabin Pond. That's viewed from the sort of eastern. East-looking west, I think. So that little gap that you can vote through there, it's escrow on either side. Sandy Gravel Ridge. I think there might be some up around just southeast of Green River Reservoir. Yeah, yeah. There's some big escrow deposits up there. Up around Norton, up in the Far Northeast Kingdom. Over in Stowe, there's a spectacular escrow in the Miller Brook Valley. There's dozens of them scattered around Vermont. As you expect in any area where you had a lot of glacial meltwater going on. And this doesn't show it really well, but a lot of our swampy lowlands, like the big peatlands over near Lanesboro and Groton State Forest, they're boulder-floored former channels that the glacial meltwater was flowing on at the surface. And here's a couple of swales that have vernal pools in them now that are unconnected with any stream systems, but they once had large amounts of glacial meltwater flowing through them. There's thousands of those scattered around Vermont. Here's a steep one coming down from a hillside above East Long Pond. It's a very bouldery swale coming down like this. And that was a very brief, short-lived glacial meltwater route as well. And here's one south of Buck Lake. It's just a big swampy area now, but based on the overall pattern of it, it's evidence of where the glacial ice was waters were draining away. And in this photo over in Barnett, over near the Connecticut River, I'm standing in a big hollow in the bedrock formed by glacial meltwaters flowing over this gap in the ridge and making a whirlpool and upgrading this rock with boulders and cobbles and pebbles being swirled around. It was basically a plunge pool type spot. That's at least 100 feet above the Pesumpsic River today. There's no streams flowing through it anymore. There wasn't at one time. And George, this was happening under and within the ice? That one could have been out beyond the ice margin or under, I don't know. But the meltwater channels are often right near the edge. The Oscars are out underneath the ice. Back in a little ways. So when you're talking about ice margin, you're talking about like the lowest south that the glacier ever got? Or that it was at a certain time. Remember that map I showed of New England showing the wiggly lines across it? So it was down at the bottom in Long Island over 20,000 years ago and then retreating up to Vermont by 14,000 years ago and Northern Quebec by like 8,000 years ago. So on this map here, again you can see Sabin Pond, you can see these segments of Esker here in purple. And in red down here, I didn't tell you that, but that's a delta from a stream that had been flowing into an arm of Glacial Lake Manuski. We had our Glacial Lake coming up into here and that Esker shows us that the Glacial Ice was melting and pouring out the waters from the melting under the ice was pouring out through here. Then it probably went back up to here and this piece of Esker was feeding it and then back up into here year by year. Who knows, maybe it was one year, two year, three years or 10 years, 20 years, 30 years but the ice was gradually retreating up from south to north because it wasn't being fed from up above but from up to the north anymore. You need a 3D animation on this and I don't really have it yet. That's my missing map anymore that you've seen before but maybe the colors are starting to make a little bit of sense on this. I wanted to show you a few more features. These lumpy ridges out in the open there are what are called canes. They're sand and gravel lumps the Glacial Ice was stagnating and melting the water's sediment wasn't deposited by flowing very much it was basically stagnating around these areas and wasting away. It's an indicator of a somewhat stagnant ice situation. These are just North and Nichols Plains. We have a whole bunch of those on our property much bigger than that. Really? Where is that? Bottom of Woodbury Gulf. Sounds interesting. See because sometimes I go and look at these ridges and it turns out I dig in them and it's bedrock there. It just hit ledge. It's more interesting when I find the sand and gravel deposits. Here's an example of a kennel hole. This is over at the Neil Farm in South Woodbury. It's a place where there was a block of glacial tail or glacial ice surrounded by sand and gravel. That's over on the right is the sand and gravel and where the pond is now was a block of glacial ice that largely melted away leaving a hollow and because it was on the groundwater table it becomes a pond. So you've got kettles scattered all over them through the valley portions of the woodbury. Do you have any ponds like that on your property? Not really. I've seen a whole bunch of those down in southeastern Massachusetts. You would have. There were thousands. What towns are you thinking of there? These were in the town of Plymouth. Oh yeah. Plenty of kennel holes down there. That's glacial geology central down there. So here's some sand and gravel deposits over in Walden. And these deposits are layered which means that the waters were flowing and changing in their energy. So some sort of glacial stream and very small pond deposits. I'm not going to get into details on it but quite thick. I mean that's a 50-flood high bank there. Sand and gravel. Here's a slightly closer view of the material. That was Devlin who was my field assistant back in 2016. He loved digging. Okay. So I just want to talk a little bit about glacial lakes here. But also let's see how we do it on time. Let's see. Time changes. Well if people are okay I'm going to go through a bit more and take you on a little tour of our glacial lakes in Vermont. There's a whole bunch of them. And what happened is that story that I've been repeating about the glacial ice retreating from the south to the north over several thousand years. There was a glacial lake in the Connecticut River Valley on the eastern side of the state that is quite extensive and this map doesn't show it all. That lake formed because of a damming of the valley down at Rocky Hill, Connecticut. So the waters of the Connecticut River Valley were dammed by some glacial deposits. And at first the lake was very short only taking up part of the Connecticut portion. But then the ice retreated up into Massachusetts and the lake got longer and the dam largely held and the ice kept retreating up through Vermont and it was still held for something I don't see in 3,000 years or so. And we have some very interesting ways of dating the deposits. We're not really going to go into it but there's some very precise analysis done of how long some of these lakes lasted. So Lake Hitchcock so-called after an early geologist over in the Connecticut River Valley is our longest lived one in Vermont. And then there's a series of lakes that formed over in the Champlain Valley and then a very large lake in the Winooski River Valley that actually connected through stove up into the Lamoille River Valley. And there's some others in other places that just aren't shown yet because we haven't made the maps. That's what we're working on. So that's the map view of glacial lakes. And this is a funny chart that we're trying to show that there were different lakes in the Champlain Valley, the Winooski River Valley and its tributaries and over in the Connecticut River Valley. And Lake Hitchcock was the earliest I think that's 1,300 to 1,400 in Vermont. Just in the Vermont range. And then we had a series of lakes that formed in the Winooski Valley and I'll explain that. I've got some slides that show that pretty well. And then the Glacial Lake and what's called the Champlain Sea that filled the Champlain Valley that there's an interesting pattern with those talk about in a minute. But all of them were relatively short-lived except for Lake Hitchcock. And then I have Lake Champlain taking up a lot of space at the top. That's after the end of all this glacial stuff. So what is a glacial lake? Anyone done to Alaska? Paul's been, I know. Anywhere where there's a glacier coming down into an area that might get restricted in some fashion where the drainage might get restricted a glacial lake can form. So here's a glacier in the background on the Kenai Peninsula. It's flowing this way. This ice is moving day by day. If you put some flags out on that ice in the summer and watch them they'll be in a different position the next day, the next week, the next month. So that ice is moving and melting out here at the outer parts with icebergs breaking off. Well, there's some sort of glacial marine out here that blocked it. That's an end deposit of a glacier and then there's a barrier beach made by shore processes by the drift of the currents depositing sand that's blocking up that lake there. There's no way to form a glacier lake. Another way is here. I showed you a picture of here's the glacier, here's the lake and I showed you a picture showing the barrier beach down here. Well, up glacier always in a little side valley there's this. That's a lake that is dammed up by the glacier ice because it goes up behind there and waters are pouring in from the melting ice and maybe from rain and snow melt on the sides and that stuff in front here that's glacial ice. What it often looks like. It looks like dirt because it's carrying a lot of dirt. It's probably more ice than dirt but I'm sure it's messy stuff. So what's happening there is that lake is building up periodically and getting so high that it breaks out and it looks like a little thing but it's causing floods down in the lower lake down in the bottom down here. So I don't think they let people go in that lake anymore because the glacial surges are too dangerous they don't know what's going to come roaring down through there as far as big blocks of ice masses of thousands of cubic yards worth of water pouring through at a dramatic rate. So that's a tiny glacial lake. We have bigger ones. Vermont hit some pretty good size ones. And here in Woodbury, here's this map running to be the last time, Sabin Pond Greenwood Lake and we had an arm of glacial lake Winooski coming up into here somewhere around here, not getting up into Central Woodbury and then because the lake went all the way around through Stowe and came up through the Memorial River Valley it extended on up through the gulf part way up the gulf not all the way to Greenwood Lake and there are so small deposits of silk clay the best one you had to be there you have a dollar general everybody knows the dollar general when they put it in they dug out the bank behind there and there's a beautiful glacial lake deposits there, a few days a friend of mine called me and they drove up and I got to take some pictures of it and then it's gone never be seen again maybe the blast over or whatever so that's the life of a geologist you don't move when you've got the exposure you may not have it photos to prove it but why I didn't show it I don't know I got that photo somewhere so we'll take a little better tour of these glacial lakes in the Winooski Valley and I think it's probably going to wrap up after showing the glacial lake tour I think okay so this is in a bleak view showing where's Camelshump here's the Winooski Valley here's Williamstown and Northfield the Dog River Valley Montpelier Berry Woodbury yeah Woodbury there's Woodbury Mountain yeah so Woodbury right up in here we should have let's start a little earlier this is the imagine this white is the glacial ice it's gotten up to central Vermont well there's a ridge of hills going across here nowadays the white river drains down here the first branch of the white second branch they drain to the south this is Williamstown Gulf this is Rocksbury I'll forget sometimes I call it Rocksbury yeah what's that it goes down through there basically it's it's the different roads Brookfield is below Lake Williamstown that would be Rocksbury Hancock Grandville this one's Grandville and that's well that's Rocksbury Village right there and then that's the next gulf over I forget I forget what that was anyway so in each the ice was to the north and in each of these green valleys that predated the glaciers waters were impounded just like that little glacial lake I showed you they rose up until they were able to spill out and move southward into the white river valley so we had a series of separate glacial lakes that left behind some deposits sand and gravel and silt and clay and then ice melted back further so Montpelier is no longer under the ice but it's under water and the same with Williamstown, Berry Northfield, Whitsfield Warren they're all under water Brookfield well you're still under the ice Plainfield's under the ice probably Marshfield at this stage on this but so you already have a pretty large lake encompassing these valleys that we drive through today and sand and gravel is being deposited on the margin silt and clay in the back and then okay now here's the latest stage glacial ice is retreating over towards the Champlain Valley there's still a lot of ice over there UVM is under water Middlebury's already out from under but Burlington is under the ice still and so these glacial lakes that existed for a little while up in the these north flowing valleys have coalesced into a new lake that is still flowing out through Williamstown Gulf because that's the low spot the other gulfs are higher and so they're not operating anymore waters are still flowing from this huge lake coming in from rain and snow melt and glacial melt waters and pouring out through here Williamstown Gulf has huge amounts of water going through it for some decades to centuries and this is sort of the details of the fact that we look at shoreline deposits special places where we can see identifiable shoreline sand and gravel deposits and they tell us where each of these lakes were and the surface that we get a lake surface that would have been as level as a bathtub surface the day it formed they're now tilted because the land had just been released or was being released from the weight of all this glacial ice and was tremendously pushed down the land was submerged by hundreds of feet and it's been rebounded the same process that's going on today up in northern Canada and Scandinavia places that have been more recently de-glaciated their land surface is measuring is being uplifted so fast it's easy to measure did you have a question? yeah so our landscape has responded to that even today 14,000 years after the glaciers have retreated our landscape here in northern Vermont is we think still going up at a very subtle rate but it's hard to measure the order of 1 to 2 millimeters a year but you gotta have something to compare if a surveyor went out and measured between one point in Woodbury and a point in Calis every year they might be shifting a little differentially but how would you know but the most precise types of GPS positioning that surveyors use now the very best that sort of thing so it's being documented all over the northern regions even rates of a millimeter a year over a decade or two you can start to nail it down this is a photo from Norway I didn't take the photo but I was here it's a spectacular valley in the Ultraman mountains and here's a big lake in a glacially scraped out valley big U shaped valley and streams are coming in at the upper end and the outlets way down here and these are delta deposits streams come down to the lake and they slow down because their gradient has dropped and they drop their deposits and delta deposits like that modern one are exactly what we look at to figure out these little glacial things here's a delta viewed from above that's probably several hundred feet across that field of view formed by a delta at Cotton Brook on the west side of the Waterbury Reservoir where there's a large landslide that was highly active in 2019 it's still active that's a site we're studying but that's one of the most spectacular deltas I've seen in a while the deposits come right down they grade right to the lake level and if Waterbury Reservoir was drained and these and these deposits were vegetated over and didn't erode away you could come back 10,000 years from now and have a very good idea of what the level of Waterbury Reservoir was but they're also very erodical too so they may not be there in 10,000 years and this is this is what some of these glacial lake deposits this is Lake Hitchcock deposits in the upper Connecticut River Valley and this is where the glacial lake level was and these are deposits far out when the these deposits hadn't yet pushed out over them these are in the lake deposits and these are kind of more edge of the lake deposits that are building out over them but it's just an example of how vast some of these glacial lake deposits can be and they've been major sources of sand and gravel for the last century they're all over, quite spectacular at times and I'm going to wrap up on some of the other glacial lake deposits they're a very complicated set of deposits here that we're not going to really dive into but you can see that there's a very strong set of lines that go across here those lines represent layers, planes like leaves in a book like pages in a book stacked one on the other and sometimes those layers can tell us a lot of really useful information okay, dime for scale and you're dying as well in my thumb so those lines represent annual layers in glacial lake Winooski they're on the shore of the Waterbury Reservoir, that's the modern water body there in here but I'll show you another slide but this one works well too there's light colored wet layers and dark layers you see them over and over again and they form a pattern just as tree rings form a pattern where you can look at trees in a region and look at one tree after another and if their growth conditions are the same you can say okay I can figure out what year I'm looking well these layers called VARVES V-A-R-V-E-S it's a Swedish word they can be mapped out it's a very painstaking word work to measure them but if they're measured and compared with other places and put in sequence and order you can figure out the year by year history because what happens is these are deposits that form deep in the glacial lake far away from the edges, far away from those streams that make deltas like those and they gravel deposits I was showing you instead in the summertime out in the middle of the lake fine silt and sand can wash out there are little currents, gentle currents carrying that stuff out into the lake and the waters are just a little bit in motion in keeping finer materials from the clay suspended in them so every one of those light colored layers is a summer layer and then what happens with the lake in northern New England even now when it's winter time when it's the lake too it frees over and that landscape used to freeze up so much that basically stream activity slows down to nil not entirely going through some of the streams but basically the lakes shut down the inputs to them so there's no longer much sediment coming and here's another site here's a good one here's a light colored layer that's a summer layer this darker layer is silt and clay it's the finest stuff it's so fine that you rub if you rub it between your fingers you can feel it a little but it basically gets lost in your fingerprints really tiny stuff the clay is so fine if you get pure clay you can lick it with your tongue and you can't even taste any grit that's good stuff for pots do we have any ceramics folks here and you can tolerate a bit of that silt I think it depends what you're doing you don't want too much sand in there I wouldn't think just the right amount it depends on what you're making it depends on what you're making well this is pretty good pots I don't know about that but it depends again what your requirements are but so these lake deposits have been studied throughout New England starting in the 1920s and we worked out a chronology for the glacial lakes and then using things like radiocarbon dating we've been able to tie those relative ages to absolute ages so that's how we made that map of New England showing the age of when the ice the ice margin was in different positions because these lakes followed the ice the water was pouring off and so basically as the ice melted back the lakes expanded after this was a site that I looked at behind the just behind and to the left of the police station in Montpelier it was another one of those temporary exposures Brett Engstrom called me up he said, George you gotta see this in his best excited way George you gotta get out here and we talked to the owner and he thought we were crazy but I brought my ladder and we had over 200 years worth of glacial lake history and here it is it was raining it was November it was really cold and I wonder rain maybe right when that photo was taken and I volunteered to do the ladder because some of this stuff they just dug it out some of this silt and clay was popping off the face because it wasn't stable they were about to build a retaining wall but we got in there before they did we got two days I think it's five or two every five barbs or years I put in a golf tee to keep track of it I measured the thickness of all the summer and went to the layers and it actually matched up very well with the other sites we had in the in the landscape river valley so that one's gone too never to be seen again and just so you know the next time you go to downtown Montpelier this is out in front of the Kellogg Hubbard Library this is an artificial field of some sort and then I believe some stream deposits and this is our clay silt and clay I couldn't really do anything with it but there's your lake deposits down underneath our feet in the valley bottoms around here so there's cool stuff to be seen there's some clay on U.S. Route 2 a spot that has repeatedly swamped just as in the side there were some pretty large brickyards in much of the Winiskey Valley Waitsfield, Essex and Waterbury those are some of the historic sites but we had them in Plainfield Marshfield, Cabot anything up in Southern Woodbury anybody know of a brickyard in your older history here you might not have one but they're all old okay that makes sense there's one up in Craftsbury I've seen that one I've seen the site I've been shown the site and seen some old bricks there so it was once a widespread cottage in larger industry so we've taken a tour of Woodbury and we haven't explained everything but I think this is probably a good stopping point maybe as you travel around and as you dig in your gardens and all maybe this will give you some background after a minute I will go to a slide that has some references and stuff but wonder if folks have any questions I'll be happy to answer them yes sir rocks strewn about Woodbury how far might they have traveled they just come off the nearby one in my front yard I just got a shear off of the granite quarry or did it travel miles if it's a piece of granite it probably came from the next granite mountain to your north however we have seen boulders not one in a hundred it's probably one in a thousand but they stand out because they're different we see different boulders here and there that clearly come from outside Vermont even there's some nice boulders the metamorphic rock that have been traced back to the pre-Cambrian rocks in Quebec which makes sense so they're called glacial erratics when they've been moved from their local rock onto some new rock up in Craftsbury there's a very particular granite up there the bullseye granite of Craftsbury has anybody ever seen that yeah, yeah it's very distinctive and it occurs as bedrock in a very small area but roughly south of there south and a little bit west I forget the exact direction the boulders are scattered for miles and we know they go back there it's like putting the jigsaw puzzle back they're that color they just go right there to that one spot in Craftsbury so when somebody could find a unique type of boulder and use it as a tracer it's very useful but 99% of the boulders come from within probably 10 miles to your north and immediately to the south of every one of our granite hills like where, yeah, here's the here's the quarries there here's your big granite quarries there's granite boulders all over here and they're from here but you've got other scattered bodies so what part of town are you in? right under the quarry, you just had your thumb on it it's terrible I think we figured that one out and granite seems to be particularly good in making big boulders because at times the fractures that break it up in the bedrock are very widely spaced that's what the quarry people want they want to get they don't want it to finally broken up granite that they get and the upper parts of the rock they want to get down a ways while the glaciers also scoured and plucked at the high peaks this is the exception to saying that streams largely shaped our landscape because the glaciers, yeah, they shaped it they scoured away all any loose soil, any kind of rotten rock that they could get their fingers on the glaciers just plowed it all away and tore away at the bedrock a fair bit too there was an old study and I don't know if it's any good anymore but the thought was that New England had been lowered on average, just average for whatever good averages are for something like 3 feet or so by the glaciers coming and going and I forgot to mention they came and went many times in that last couple million years but anyway I worked that in at the end so other questions yes on an earlier slide you were showing the little purple X's that went from Valley Lake to Savin pond but there wasn't anything connecting Greenwood Lake to Valley Lake or Dog pond and we live on Greenwood Lake and we know that we can kayak across the lake and we can walk on that neck of land from Greenwood Lake to Dog pond and they're really connected so I was kind of surprised that there wasn't any sort of visual connection from Greenwood to Dog pond actually I think there is I live on Dog pond and I've gone through that cut lots of times and that the Esker continues just for maybe 100 yards or so into Greenwood Lake I didn't see it I missed something I made a mistake I'm going to show it all the reds on it I don't know so Greenwood there's nothing connecting Dog pond to Greenwood there and I'm kind of surprised about that because I didn't see it there could be something there is one right by where that lowest lobe of Greenwood Lake comes from so you got something I don't know do you know is it on the northwest or southeast it's on the like a ridge of sanding right you get up there and check it out yeah other questions I have a question about the Eskers I've just been confused about whether there's water running I would think it would be washing stuff out it was washing stuff out however it was carrying I didn't bring the right slides for this but imagine a river flowing with a heavy load of sediment in it it's in flood and sand and gravel is just being tumbled along and it's just the water is moving so fast but it's just churning with sediment moving things of all sizes including boulders and imagine you could just shut the water off suddenly and deposit all that stuff and you can't really do that with a stream but with a subglacial stream all you have to do is the ice has to just shift a little bit and it can shut off the source and all that sand and gravel is in motion just stops it's like a kid's game everybody stops, frees and it just goes and so it's a pile of sand and gravel but it's surrounded by ice and if the flow doesn't pick up again and the ice melts it's going to be left as more stuff than the glacial ice around that had sediment in it and the way down and the huge pile of sand and gravel in the middle ends up standing up in relief so we need an animation to see that I'm happy that they have the cartoon version I'm sure that Novo or Nature could do a really good job on this but I don't think they could other questions one of your first slides with the temperatures over ages and ages that midline is that an average of 32 Fahrenheit and then it gets sometimes it's present day average on that one I don't know for sure we're roughly how cold were we talking back when it was the way to answer that is to go to another slide skip a bunch of stuff but I don't show you because I think it would help so alright we're going I'm going to start with this this is like let's start with this this is the last five and a half million years showing global temperature based on the ice core data that they have the Vastak ice core and so five million years to the present and I think this zero is supposed to be some sort of approximately present day average or mid 20th century average is often what they're using and this shows you the temperature was a bit above that until depending on how you decide to count it about three to two and a half million years ago when it started dropping and this is the glaciers coming and going there's over two dozen glacial events that happened largely to a great extent worldwide in the last couple million years so we used to think there were four those the marine records and the ice core records really added a lot to that so the climate fluctuated a lot and then we're down to the present day right down in here somewhere but I've got a more detailed slide to show that to answer your question so that's the one you asked me about and I think that present day average but I don't really know but this one if you ignore all the wiggles and just look at the black line which is the best fit line through here from 12,000 years ago to the present and with a detail for the last 2,000 years because it's impossible to show otherwise this zero line is the mid 20th century average so it was warming there's that 10,000 years before present here's our warming and then fluctuating around and then in the last 2,000 years here's your same black line and fluctuating around that's probably the medieval warm period that's the little ice age and then boom here we are today and we're off and running and that's 114 since then we need a newer graph so does that sort of answer the question so we haven't seen temperatures like we're getting today for a long time we can go back far enough in Earth history so we had temperatures as warm as today but it wasn't really the same Earth the ocean circulation pattern was completely different the continents were in totally different places it was just not the same place no time in the last several million years have we been in time that we seem to be moving towards right now so maybe one last question and I'll be happy to continue after people have a chance to stretch and go on your way if you want I was reading a Susan Sawyer's book that she wrote for this area big for the Land Trust and as she was working on it finished it a few years ago but the she mentioned in there that after the ice left there was no life in this area no plant life no animal life so I was just thinking about that and I said where and then things started to recolonize with the warmer temperatures so was it wind that brought in seeds and things from the south or were there memories that sprung back from before the three million years it was everything and it's not the exact same thing but I was in Iceland looking at glacial moraines right up against the ice and I was my wife and I were standing on a marine recording where the ice was the previous year and that's a maritime climate it's very moist, it's very warm but there was pioneer vegetation on that marine and as life followed the ice back it didn't lag I mean there were there have been seeds dispersing on the ice and in places that are moist enough you go to coastal Alaska that wasn't us but go to coastal Alaska and there's forests growing on some of the glacial ice on some of those glaciers so that takes a moist warm climate to pull that off and a special place to also have a glacier there nothing but so there wouldn't have been forests on the glacial ice here but the landscape probably pretty rapidly got and we have pollen cores recording this I can show you all this stuff I thought it was on the mountain okay Matt Peters shared this slide with me so here he is up in Quebec modern day we went on a backpacking trip up in northern Quebec maybe Paul does have you seen terrain like this? sure, yep okay this is vegetated terrain much more recently deglaciated than us I don't know but probably since it's so far to the north I don't know what the people up there have determined so this is several thousand years worth of revegetation maybe but you've got all sorts of vegetation but the soils are still developing you've got a scattered maybe taiga type vegetation, scattered spruce black spruce jack pine maybe tamarack even but you're not going to have big vast forests and why that area is open and how long it's been open I'm not sure in the first couple thousand years after the ice retreat the landscape would have dramatically vegetated the pollen records and bogs and lakes show that but it did take time because you've got to build up enough of a soil for whatever plant animal communities to get going so we had forest certainly scattered forest within two thousand years but I can't remember exactly how quickly well I think we should probably stop at this point I'd be happy to answer more individual questions thank you Jordan thank you