Barrier Islands
Dr. Jesse Reimink: [00:00:00] I'm recording.
Chris Bolhuis: So am I. All right, let me get my radio voice on. You ready, Kermit?
Dr. Jesse Reimink: I'm, I'm ready. Kermit.
Chris Bolhuis: we go.
Dr. Jesse Reimink: I I forgot that Jenny called me Kermit. That's so [00:00:30] funny.
Chris Bolhuis: She did. We actually listened to a couple podcasts on the way back. We, uh, just got back from Louisiana on a spring break trip, and we listened to some podcasts and she's like, oh, Kermit.
Dr. Jesse Reimink: Kermit's back.
Chris Bolhuis: yeah, there he is. There he is. Missed that little guy. Yeah. Somehow I, I don't buy it. How you doing, Jesse?
Dr. Jesse Reimink: I'm good man. Hey, this is a timely episode because you just got back from spring break, your high school spring break in Michigan, and this is a time when a lot of people from the Midwest [00:01:00] migrate down to barrier islands and spend vacations on, around or near barrier islands. And Chris, you, you guys go to Louisiana, right?
Chris Bolhuis: We do.
Dr. Jesse Reimink: Did you see a barrier island at all, or were you mostly around Lake Pontchartrain?
Chris Bolhuis: Yeah. We were on the north side of Lake Poncho train and so we did not. Sea barrier islands, but I've spent a lot of spring breaks on barrier islands before. You know, like for instance, you know, Tybee Island in, in Georgia, , near Savannah,[00:01:30] , is a barrier island. And it's just, it's, they're awesome. So, Jesse, give us a quick rundown on where we're going today. What are we gonna talk about?
Dr. Jesse Reimink: Yeah, we're talking about barrier islands. We're gonna sort of briefly intro what they are, what we're talking about here. we're gonna then move into the things you need to form a barrier island. And really the, the theme of this episode is what are they geologically and why are they relevant as usual. And so we're gonna talk about like the things you need to form a barrier island. We're gonna talk about. [00:02:00] Models for how they form and how they then therefore evolve and, and these things evolve on human time skills. So that's a big topic. And then we're gonna sort of end by talking about the human functionality, like the why we care about barrier Islands and why you should care about Barrier Islands.
Chris Bolhuis: and we should care about Berry Island. This is,
Dr. Jesse Reimink: totally.
Chris Bolhuis: I think this is a really cool episode idea because it's relevant. I mean, , it was really relevant during hurricane season, this past [00:02:30] fall, with what happened in Florida and, you know, which is basically surrounded by barrier islands. So, yeah, this is, it is timely,
Dr. Jesse Reimink: It's a great one. Kristen, and you just brought up a really good point, and I think we should start there, is what are these things, why are they called barrier islands and they serve as a barrier. It's an island that is a barrier from, you know, ocean wave activity to the mainland, and so they're ubiquitous. Around the Gulf Coast in, north America, they're very prevalent along the Atlantic [00:03:00] seaboard of North America as well, at least the Southern Atlantic seaboard. And these things are, are all over the world as well. They don't always occur right on coastlines. They sometimes occur out, , away and, serve islands as well, but they're very common globally and really important because they protect the mainland from wave action and storm.
Chris Bolhuis: All right. Jesse, let me interrupt you a second. Let's give a description of what barrier islands look like. We want everybody to, to be able to picture these things because like you said, dropping big words, ubiquitous. [00:03:30] they're, they're very ubiquitous in the eastern part of the United States, and they're all around the Gulf Coast and so on. There we go. So anyway, These are just these sand deposits that basically they're disconnected. It's not a con, it's not this continuous chain of islands that's out away from the mainland shore, but they're parallel, disconnected deposits of sand. That's what these barrier islands are. So, Jesse, have you been, what barrier islands have you [00:04:00] been to that are fairly well known?
Dr. Jesse Reimink: oh man. I've been to a lot of like the smaller ones, uh, around really on the Gulf side and the Gulf of of Mexico. you know, Destin's on one, Navar, there's a barrier island there. I forget the names of the actual island, but these are little towns, little sort of vacation towns on barrier islands. It, But, but they're sort of all over and there's lots of little towns and I always, get confused about what the name of the island is versus the little town we're in that's on the island. You know what I mean?
Chris Bolhuis: Yeah. And, and you're right about that too. It's a cool thing is you often get these quaint [00:04:30] little, like popups on these islands that are just so cool, you know, with the, tiki bars set up and restaurants and just, they're often very quaint, cool environments there. Um, I've been to Tybee Island. In Georgia many, many times. I love that. I've been to Skidaway Island. There's a state park there that is absolutely one of my favorite places on the planet. , the one that made, you know, headlines big time this past fall with the hurricane season was Sandoval Island in [00:05:00] Florida. just absolutely devastated this fall, Miami Beach, Atlantic City. These are barrier islands, and these are just some of the famous ones there. There are literally hundreds, if not thousands of barrier islands up and down the coastline of the east in the Gulf of Mexico.
Dr. Jesse Reimink: Yeah, Kristen, these aren't just a us uh, phenomenon in Australia. Morton Bay is a big one, , bribe Bay. There's also in New Zealand and in Europe, there are massive barrier islands that are really important [00:05:30] ones. Importantly, there's some in the Baltic Sea and the Wadden Islands stretched from the Netherlands to Denmark. So these are really kind of important things globally from a geoscience perspective. And, uh, they often exist. Somewhat pretty areas and, around big cities because they often protect like harbors and things like that. , So Chris, I think this is a good time now to transition into how these things form or how we think these things form. and so where do you wanna start with that process? Because this is, again, [00:06:00] could be a lengthy discussion. I think so. So you frame it for us.
Chris Bolhuis: it seems like a dumb thing to say that we don't really have, a consensus on barrier island formation, but that's, that's okay. One, I wanna say that that's okay, but two, not all barrier islands are the same, and so there are gonna be little nuances in the formation of different, you know, the Geology is gonna determine. Individual barrier islands conform. So
Dr. Jesse Reimink: Yeah, and I think, let me just step in there really quick, Chris, because I, this was [00:06:30] an interesting episode to put together from my perspective because I always assumed that Bayer Islands were relatively straightforward geologically, and I had one of the ideas. One of these three scenarios in my head as the one that's like universally accepted. I think you might have had a different one in your head as thinking universally accepted and then, you know, and building this and learning about, it's like, oh wait, there's actually a decent amount of debate about this. So it was kind of a, a fun thing to learn about, uh, just putting this episode together. So, uh, just a side point, sorry to interrupt [00:07:00] you there.
Chris Bolhuis: no, no, that's good. That's good. The thing that we do know, we need three basic things to form a barrier island. All right. We need to have sand. We gotta have a sand supply, and we have to have a broad, gentle sloping coastline, which we cut in Geology. We call that like a passive continental margin, right? Or in other words, the trailing edge of a continent. And that's why the east coast of the United States is ripe for [00:07:30] barrier island formation because. The North American continent is moving in the Southwest direction, which means the East coast and the Gulf Coast are the trailing edge of the plate. All the actions on the West coast, very little, geologic, tectonic activities going on in the east. And so you get this broad, gently sloping coastline. So that's the second thing that we need. And then the third thing that we. We need waves, we need tidal currents, but, and they have to be strong [00:08:00] enough to move a substantial amount of sand. Then there is a, like a sub-bullet to this too, that we need it to be a wave dominated environment and rather than a title dominated environment.
Dr. Jesse Reimink: Yeah, and I think Chris, we need to just, just touch on this a little bit and we'll come back to this point, but sand is the key component here. Like this is not berry islands are not mud, they're sand. This is sand dunes. These are sandy beaches. Part of the reason they're so beautiful and people build little cities on them and, and big cities is [00:08:30] because they're so beautiful. the sand, that's a higher energy movement of water that you need to move a sand grain than you do to move a mud particle. So sand, we consider sand as, as sort of a moderately high energy water will move. Sand and low energy. Water will not move sand around. So that's why we have to have this sort of wave dominated. area because we need the waves to be high energy enough to move sand around like that. That's fundamentally what's going on is we're moving sand up and down to do this. So I just [00:09:00] wanted to, to sort of touch on
Chris Bolhuis: No, that's. that's. a really good point. I mean, to just maybe reiterate this, the three common rocks that are made up of these like classed particle sizes. You have shale, which is made up of, clay size or mud sized particles. Then you have sand, which you just described, which is a moderate moderate to higher energy deposit waves and rivers that have a good swift current to 'em and so on. And then you have conglomerate, which is made up of gravel sized pieces, which is much, much higher [00:09:30] energy. So the, the particle size that make up the rocks is really indicative geologically of the environment in which formed. So that's a, that's a really good point to make. All right, Jesse, here we go. Let's get into the three ideas, the three ways in which barrier Islands can form. So can, I'm gonna start off with the first one because this is more of like an older school and you know, you always rip on me for being older guy, and
Dr. Jesse Reimink: Chris.
Chris Bolhuis: wrong, [00:10:00] but
Dr. Jesse Reimink: and so I mean, yes. Why don't you take the first one, the old school, Chris, going back to the 1930s bringing us scientific theories from the thirties.
Here
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Chris Bolhuis: All right. That's right. That's right. this idea which, which does happen. I think it's important to, again, reiterate that all three of these do come into play. this used to be the common idea here's the idea, let me describe it and then, then I'll, I'll go with where I was gonna go. This theory is [00:10:30] basically it's Beach Ridge Submergence. In other words, where we have these barrier islands, this is where the old shoreline was during times when sea level was lower. Okay? Like for instance, during the last, ice age, at the peak of the last ice age, there was so much water locked up in ice, that sea level lower dramatically. and so the rivers were bringing their sand. To where that older shoreline was forming Deltas [00:11:00] and dunes, these beach ridges. Right. And they would be, you know, the shape of them would be basically parallel to where the shoreline is today, just offshore from where we have it now. So it makes a lot of sense. , if you look at a map of barrier islands, you're like, oh, well yeah, I can see where sea level would be lower, dunes would form here. Deltas would form here. Lots of sediment supply because of the, ending of the last ice age. It was very wet and you know, rivers were [00:11:30] rigorous and moving a lot of stuff. And then since that time when sea level rises, all of this deposit just gets reworked into these barrier islands. So that's the basic gist of this theory
Dr. Jesse Reimink: Chris, but I think this is a, this is a good point. Let me just interject real quick there and say, you know, as you noted this, is that you still see this in textbooks, right? And this
Chris Bolhuis: Oh, sure. It's, it's in mine. It's, It's, still in mine.
Dr. Jesse Reimink: Yeah. And, and it kind of points to this really unfortunate [00:12:00] lag that we have between modern thinking at the deep levels of topics and what's represented in the textbook still. Cuz like textbooks, you know, even though they get rewritten, the, the ideas don't change necessarily that much in the textbook view Anyway. All right. Number.
Chris Bolhuis: All right, go ahead Jesse. This is okay. New school here.
Dr. Jesse Reimink: New, new school. So this is, uh, the
Chris Bolhuis: new, but.
Dr. Jesse Reimink: area, I guess. Yeah. Uh, the offshore bar three. This is the second scenario, , that you can form barrier islands with. And [00:12:30] basically the way this works is as waves sort of move into shallow water. They start to churn up sand. We talked about this energy in that wave action can really move sand , quite a lot. And so when the waves break though, they lose energy. So the waves are coming in, they're moving sand, they hit something, , they lose all their energy and they lose the ability to move sand. So the sand gets dumped there and , they can deposit a submarine sandbar, which most people are familiar If you've walked out into the ocean. [00:13:00] Anywhere really. You know that there's a sandbar somewhere, like it gets deep, ? Right. Offshore and then it gets shallower and you can like stand up and waste deep water way out there. That's a sandbar. And if big waves are coming in and they hit that sandbar, they lose energy and they dump sand that grows the sandbar and then this can kind of become an emergent above sea level offshore bar that just sort of grew up.
Chris Bolhuis: Yeah. It's basically you're getting a bunch of sand that's gonna pile up because [00:13:30] as the waves come in and they're moving this sand, it's higher energy. We talked about one of the necessary ingredients being wave dominated, right? It it, because that's the stuff that has the sufficient energy to move these heavier sand grains. When the waves break, they lose energy and deposit the sand, and so as long as sea level remains, you know, stagnant for a while or stationary, then the waves are gonna break fairly consistently at this zone [00:14:00] offshore. And therefore, as they lose energy, sand gets deposited in a fairly consistent place. Okay. Are we good with number
two
Dr. Jesse Reimink: think that's good. Yeah. Pretty simple. Yeah, I think we, I think we nailed it.
Chris Bolhuis: alright Jesse, let's get in then to number three. The third idea, we know this happens too, like I said before, all three of these do play a role here. This one's called the Spit Extension Theory, and we need to define [00:14:30] this cuz this is, uh, what is a spit? What
Dr. Jesse Reimink: Right.
Chris Bolhuis: have some terms that we need to
Dr. Jesse Reimink: Oh, geology's full of stupid terms and, spit is just
Chris Bolhuis: know, but I do kind of like this one. I. It is silly, but I like it. This is very difficult to do in a podcast format because it's very, you know, shoreline features are very visual. But imagine a, a shoreline that has a bay or a, like a lagoon. Okay. In other words, an indent toward the [00:15:00] mainland of the shore. . What happens when water enters into that? The water's dispersed and it loses energy. And just as we said before, whenever water loses energy deposition is a result of this. Okay, well this is one part in terms of how you get spits. It's the sandbar that extends partway across a bay or a lagoon kind of area, of a shoreline. Okay, so that's the first thing. Now, we also though, can [00:15:30] determine what's called the longshore current by looking at the geometry of the spit. ? So Jesse, I'm gonna leave it to you cuz I've been doing a lot of talking. What is Longshore current
Dr. Jesse Reimink: Longshore current is this really interesting phenomenon. and you can watch this if you ever go sit at a beach and it's wavy, just watch this happen. The waves very rarely hit the beach head
Chris Bolhuis: I'm gonna interrupt you for a second. I'm gonna interrupt you. Sorry. Keep your train of thought, but I do wanna say [00:16:00] sitting on a beach and watching this kind of stuff to me is amazing. Watching Geology on a shoreline is, it's better than a campfire. Okay. It's, it's,
Dr. Jesse Reimink: I I agree, Chris. It's a great point. I mean, the best is to have campfire and watch longshore current going on, so a beach campfire going on. But , I think you're right. This is one of the few phenomenon in Geology that. Happens in human time scales and you can actually watch it happen. And so Longshore current is what? What's happening here is the waves [00:16:30] rarely ever hit the beach head on. So they rarely like come at the beach and hit it square. They're usually hitting it at a slight angle. And you can often see this as a breaker, right? The wave is not breaking all at once. It kind of rolls across the horizon in one direction or the other. That's the wave energy hitting at an angle. And so what happens when wave energy hits at an angle is it'll wash sand grains up at that angle. So as the wave hits the shore, it washes sand grains. At an angle. So [00:17:00] not straight up the beach, but slightly to the left or slightly to the right, but then as the wave recedes, it's just gravity, so it just moves straight down the face. So what you get is a sand grain that is brought up at an angle and then straight down and then up at an angle. Straight down, it's a zigzag. And this, you can watch this happen if you just find one sandin or one little shell and watch that get moved up and down. You'll see it migrate down shore into the left or to the right as you're sitting there. And if you add that movement [00:17:30] up billions and billions of times and billions and billions of sand grains, and they're moving meters per day sometimes, depending on the wave energy. That's a lot of movement, that's a lot of sand being moved in one direction or the other. And because weather patterns change, it'll vary day to day, but there will be a consistent trajectory or consistent trend of waves hitting at an angle on average in one angle different than another. So sending the sand grains to the right or to the left more frequently than to the other direction basically. So [00:18:00] we get this on average yearly directionality.
Chris Bolhuis: The bottom line is that you generate this current that runs in the direction parallel to the shore in the direction that the sand is moving in that kind of zigzag fashion. Okay. It, it is very cool. It is very cool. Well, and so what happens then is sand will move down the shoreline in the direction of Longshore current. And when it moves across this bay or or lagoon or whatever, [00:18:30] then it loses energy and it stops moving and it gets deposited then. And that deposit then that comes partway across the lagoon is called a spit. And what it'll do is it'll actually form a little hook that kind of curves into the lagoon. That's that hook on the end of the spit is just a classic, oh, that's a spit. Like every Geology 1 0 1 student, is looking for that classic little hook that extends into the lagoon or the.[00:19:00] All right, Jesse. We've defined what a spit is. We've defined what Longshore current is. Finish this theory off.
Dr. Jesse Reimink: It gets really easy from where you've gotten us from a spit. Okay, this, all this sand is moving . Let's say it's moving down a shore. The shore is straight, it's moving down the shore. If you're looking at a map, view hits some bay, forms a little spit. You get this hook going out. It's really easy to see how if you just continue this, you build the spit bigger and bigger and bigger and bigger, and eventually it's going. Break off. There's, you know, big, storm comes in [00:19:30] and cuts through the spit a little bit and then all of a sudden it's an island, it's a barrier island and it's just sand moving in the longshore current direction. And so you can see how this would get extended for great distances. Fairly rapidly on a geologic time scale, fairly rapidly just by building these big spits. And then they get broken by wave action. Or a big storm comes in and just cuts through that spit and now it's an island. And so I, think it's a relatively simple thing to understand.
Chris Bolhuis: uh, I don't know. We've introduced a lot of [00:20:00] terms though, Jesse. Um, so, but where these are really common is in an estuary environment and an, so here we go with an introduction of a new term. An estuary is a flooded or drowned river. , think of the, I think the most famous one in the United States is the Chesapeake Bay in Virginia. And, and so what happens then is rising sea level can flood this river mouth and leaving this [00:20:30] spit really stranded quite a long ways away from the main. And like you said, then as these hurricanes and these events come in and they really just dissect that linear geologic feature called a spit. So that's the third way that you get barrier islands.
Dr. Jesse Reimink: Yeah, and Chris, this is the way that I am more familiar with, and I think, you know, before putting this episode together, I would've said, oh, this is the dominant way, like Longshore current dominated [00:21:00] processes generate barrier islands. Now, one exercise that's totally fun to do is to look at the Google Earth image of especially Eastern North America and then you can view spits and barrier islands and see how these things kind of interact and see where these three models make sense and sometimes don't make sense for how a particular barrier island, , formed for.
Chris Bolhuis: because I would disagree a little bit with you on that. I would say that that the offshore bar, theory [00:21:30] number two that we described is I think the most common. When you look at Google Earth and you look at the map, you don't see all these estuaries that are leading to barrier islands. You just see, relatively straightforward parallel shoreline, and then these barrier islands off from it, you know? And so you can like look at it and, and see which one plays kind of bigger into that. ge.
Dr. Jesse Reimink: Yeah, that brings up a really good [00:22:00] point, Chris, and this is an interesting discussion to, that I think is, is useful for understanding why. There's a bit of debate about barrier islands is, you know, , the sand supply for instance, you think of Cape Cod or like Martha's Vineyard or these types of things that have a, a lot of sort of barrier islands or, or they, them are themselves barrier islands. A lot of that sand is like glacial sand that was deposited by the glaciers and actually why there's very few barrier islands up in Maine. There's not a lot of sand. It was all moved south by the glaciers. And so, we can [00:22:30] have at least the way I, I sort of learned it and I think the way I would have interpreted this before this episode at least, is that the glacial sand got dumped there and then it was moved around by Longshore current. And it doesn't need to be right near a river mouth to form this, but like you pointed out, there's a bunch of other ideas to, how these things form. and these three processes all play a different role, different proportions in formation of any given barrier island probably. So I think, we got those three kind of [00:23:00] across Chris, but I think the last part of this episode we wanted to focus on like, why are these super important and they're beautiful. We've kind of hit on that, but why are they really important, geologically important? What? What stands out to you in this?
Chris Bolhuis: Um, what stands out to me is the name, I think the name is for once appropriate. They're called Barrier Islands. They act as a natural barrier. For our main coastline. The barrier barrier to what? Well, they take the brunt of [00:23:30] storms. They take the brunt of hurricanes. , because , when these storms, the storm surge slams into these ridges that are off from the mainland, those ridges take the. They're the ones that get reworked and just pounded by these events, and that then protects the mainland from taking the brunt of that energy. So I think geologically from a human standpoint, they're very important. I don't know. [00:24:00] Does
Dr. Jesse Reimink: J Yeah. Just in protecting. I, I agree completely with that. I, I geologically. The best, and you and I have this sort of, well, we always have a confrontational approach to biology, I think. But they are really important for biology too, because they basically do this protection thing, which also protects a whole bunch of, , well habitats behind the barrier island, In the estuaries or in the bays behind the barrier island, between the barrier island in the [00:24:30] mainland. These are like super, super biologically, biologically productive regions.
Chris Bolhuis: That's right. Let's get into some of these specific habitats then. So these barrier islands, They have a beach side to them, and the beach side of that is the ocean side of the barrier island. In other words, the beach is what takes the full brunt of tropical storms, storms, hurricanes, all of that kind of stuff. That's what gets hit first and, and takes most of the energy [00:25:00] behind the beaches. You get these dun. That have like they're, they're very topographically diverse, right? I mean some of them can be very high. You get a lot of relief and some of 'em are fairly low line and so on, , but what they do, like you just said, is they offer protection. These dunes offer protection and they allow soil to develop on the other side of the island on that protected. The side of the island that faces the mainland. Okay. And [00:25:30] this is, one of the coolest things about these barrier islands, I think is that diversity of flora and fauna that you can get in these very protected environments.
Dr. Jesse Reimink: It's so, so, so, so cool. And I think that the sort of back barrier side, on the mainland side, I guess the back barrier. So you're, you're, you're facing. The mainland, , your back is to the ocean. , storms can wash water and sand over the whole thing, so they can go over the berry [00:26:00] island, wash a ton of crap into that, lagoon there, and disturb the ecosystem. And this is part of this. Dune migration thing. But it really protects. Like you, you don't do that very frequently. You don't do that very often. When it does happen, it's kind of catastrophic, but you know, that's a relatively uncommon phenomenon. And so it's just this protective barrier to all of the biological diversity that really likes the shallow, muddy.
Chris Bolhuis: and on that other side on the mainland side of the Barrier island, you [00:26:30] get one of my favorite places on the planet really, which is the salt marsh environment. Um,
Dr. Jesse Reimink: you do strike me as a salt marshy guy. A little bit. You like waiting
Chris Bolhuis: well, you know what
Dr. Jesse Reimink: marsh or something, don't you?
Chris Bolhuis: I, I love it because you get the smell of it. Have you like, I don't know, I, to me this is comfort food. Honestly. It really is. the time that I spend like in the early, early morning hours going for a walk in the salt marsh is one of my favorite things to do actually. If you're [00:27:00] in, you know, Louisiana or Georgia where I've done a lot of salt marsh walking before, this is where you have. Lots of alligators and, you get snakes and, pelicans and just this huge diversity of exotic life. I mean, I'm from Michigan, okay? This is not, this is not the common kinda stuff, but I, I absolutely, I, I love it. And that's on the mainland side of the beer island where you get this environment. , and you know what else too, Jesse, is that they serve a very geologically important [00:27:30] function too, is that they protect our wetlands on the mainland. Okay? And in other words, these wetlands are, they're, it's made up of loose unconsolidated material as well, just like the Bear Islands itself. And so if, you didn't have the Barrier Island protect. That takes the brunt of the energy. Then our wetlands they would be the ones that get reworked by all of these storms and, and they'd just be rapidly disappearing. , even more so than they already are.
Dr. Jesse Reimink: [00:28:00] Absolutely. And I think, so one thing to kind of close this loop, I think Chris, is to talk about the reason that these things are protecting is because they have this big emergent sandbar. They're a big sand dune that's sticking up above. Sea level and it runs parallel to the mainland. And so the value is that it's sticking up and that it's sand. It's kind of harder to move. It does not mean that they're permanent. These things move all the time. They're really kind of ephemeral. And so I think we should end with talking about [00:28:30] nourishment of these things and maintenance of these things cuz there's two, I would say, categories of risk to barrier islands. Well, maybe three. The first one is kind of natural that they move a lot, and we can touch on that at the end. But the other two, the ones that are like human induced changes to barrier island activity, one would be limiting sand movement and the other one would be sea level rise. Real quickly, how do you view these two?
Chris Bolhuis: Yeah, that's a really good point. First of all, to I think an [00:29:00] appropriate time to bring this in , when you think about how would we have affected the sand supply? Because that's what they need. Right? That's the number one thing that we said that all barrier islands need is a, a sufficient sand supply. How would we have possibly have affected this? Well, think about what we do to rivers almost always is we levy rivers and we levy them out into the ocean. In fact, which means then that the, the wetlands and these [00:29:30] barrier islands, they're not gonna get the gift of the river. Right. and geologically, the gift of the river is sed. And we're directing the river by levying it where to push the sediment. Okay. And so we can then impact the future of barrier islands by maybe diverting the sediment supply from one place to another. I think that's where my mind goes. What do you think?
Dr. Jesse Reimink: Absolutely. I agree completely with the, the sort of sediment supply side. Whenever we put [00:30:00] a big, a pier out, that sand piles up on one side and is depleted on the other side. And that's just a very small representation of what you're describing. Cutting off the sand supply from the river, really all the way out. Along the coast and stand that would eventually be moved over thousands of years, over hundreds of years, maybe even all the way along the coast by this longshore current. So that's definitely, I would say the first human induced sort of sand supply issue. The second one is, is sea level rise. And the, the way to think about [00:30:30] this is that average. Wave energy is super important for the, the movement and maintenance of barrier islands and so where that average wave energy is, like we talked about before, if you raise sea level a little bit or drop it a little bit, you're changing the height of that wave energy. And since sand is so sensitive to where the waves are crashing and how high they're crashing, basically if we just increase sea level a little bit, it'll start pushing sand. In more, more wave energy is crashing higher up on those dunes, which [00:31:00] is moving it, and it's more likely a big storm will come and crest over the barrier island and move a ton of sand towards the mainland. And so these barrier islands are quote unquote retreating away from the Oceanside and towards the mainland side at a decent clip because of sea level rise, even a little bit of sea level.
Chris Bolhuis: And that leads to what you, you mentioned, which again is another term, you said beach nourishment. If we take barrier islands and, and we build on them, then we can't just have the barrier island [00:31:30] migrating and moving like you just described. And, the most important feature of a barrier island to human development is the beach, right? I mean, we, if we don't have a beach, then we don't have anything to have structures on. And so when storms. Take sand and move it. And they can dramatically affect a Bear Island with one event. Okay. I mean, it can be a huge dramatic effect. We saw this, this fall in, in Sandal Island in Florida, , just devastating. , [00:32:00] we need to renourish that sand and, and what we're t really talking about is, is just dredging. With huge pipes and pumps and so on, and taking sand from a little bit further offshore and literally dumping it back onto the, where the beach should be, where we think the beach should be, and then just reworking it with heavy equipment. it's called beach nourishment. We're just, uh, filling the beach back up,
Dr. Jesse Reimink: Yeah, exactly. It's an interesting problem and I think this really points to, [00:32:30] it's, it's a tough one for me because. The barrier island is such a naturally active environment. We as humans kind of wanna force it to do what we want it to do, but it's naturally such an active environment that we kind of have to, we have to work with it a little bit, and we have to figure out this balance of how much do we artificially maintain, how much do we let nature take its course? How much are we inducing by climate change and sea level rise, and how much do we need to worry about that? Moving things around and changing the dynamics of these, it's just a super complicated problem [00:33:00] and. Don't know how best to approach it, so,
Chris Bolhuis: Yeah. I, I don't either. I guess, something that you and I get a little irritated about, I think is, you know, when you think about barrier islands, they are so often, know, they're in the news a lot, especially during storm season, hurricane season. They're often described as these very fragile systems and, and geologically. We look at this and we think, well, not really. , they've been around for thousands of years , and they're really not that fragile. Where does that [00:33:30] come from? Because geologically, you and I agree that, well, they're not really fragile ecosystems.
Dr. Jesse Reimink: They're constantly moving, for sure, and they may be fragile when we think about climate change, like huge global scale changes. If sea level rises, human induced sea level rise, then they become fragile ecosystems, but They're not naturally fragile places. They're moving and , they're sort of ephemeral, but they're not fragile. And so this was summarized really well with a quote, so I'll just read a direct quote. This is from Patrick Lynch here, and I, I kind of paraphrase a little bit, but, [00:34:00] he writes, sand islands are almost as fluidly, changeable as the seas around them. Only when we build fixed structures on these dynamic variable strands do the islands begin to seem frail In reality, it is our buildings, roads, and bridges that are fragile when we construct them on shifting sand. And Chris, I just kind of love that quote, like I think that frames at least my attitude and I think kind of yours as well, a a about.
Chris Bolhuis: I could not. Think of a better [00:34:30] way to end this episode with that quote. I think it stands alone. I'm serious. It, it, it sums it up, about as well as I've ever seen it
Dr. Jesse Reimink: And I think, you know, it, it frames the problem, like it is a complicated problem here to, consider what, what rules should we impose on buildings on Berry Islands? Should we just, you know, outlaw it or, or how should we think about this, right? Like, there's a huge range of scenarios to this. So anyway,
Chris Bolhuis: Hey, real quick. I got one thing that I want to talk about, Jenny [00:35:00] and I went kayaking in the bayou. On Friday and we pulled off along a, um, it was the inside of a bend in the, in the river. And so there's this nice sandy beach there, right? So I pulled the kayak up onto the beach and I'm standing, you know, maybe three or four feet away from the water's edge. And, , I'm on solid, moist sand, right. And then I shifted my feet a little bit, and I noticed that my left foot started to [00:35:30] sink into the sand and was soon covered in this really, really wet mud. And I'm like, Hey, Jenny, get over here. You gotta check this out. So I moved to a different part of the, beach of the shoreline and I'm like, this is what happens with Liquifaction when you take this place that has a very high water table and it's built on loose unconsolidated sand and you put weight on it. Like buildings and structures and things like this, and then an earthquake comes along, [00:36:00] right in a Jenny Bull heist, and you put weight on it and you jiggle the sand. With an earthquake, an earthquake happens, right? And the building sink down into it because the water table rises up. And it was like, so we actually got our phone out and I did a little five minute, um, lesson on Liquifaction on
Dr. Jesse Reimink: the, uh, very cool, uh, very, very cool. That's great. I, yeah, that's a great example just for another term unrelated to Berry Islands, but we'll [00:36:30] just throw another geological term that we've talked about into the
Chris Bolhuis: to totally unrelated, but I, but my point is, is look, Geology is everywhere. Geology makes the world go round.
Dr. Jesse Reimink: Yes, it is everywhere. And, you know, pay attention and you'll see Geology around you. It's totally cool even on vacation. So good. All right, Chris. Hey, that's a wrap. You can follow us on all our social media. We're at Planet Geo Cast. You can, , like, subscribe, support us. You can go to our website, planet geo cast.com, shoot us an [00:37:00] email, planet geo cast gmail.com. And uh, last thing, if you. Learning about Geology, learning the basics. This was kind of a, a basics, thing or kind of a deep dive into barrier islands. But if you wanna learn the basics of geoscience, just Chris, as you teach it in your AP Geology class as I teach it, the first class you'd get in a college level Geology course, , you can. geo.camp courses.com. That is our audio textbook for the geosciences. Check it out. It's free and uh, we would love to have some [00:37:30] feedback.
Chris Bolhuis: I have one question for you, before we sign off. Jesse, one very important question. Are you ready?
Dr. Jesse Reimink: boy. Yes. I'm nervous.
Chris Bolhuis: So who has seen the most rocks their lifetime? Me or you?
Dr. Jesse Reimink: Ooh, loaded question. Uh, we've seen a lot of rocks together.
Chris Bolhuis: Jesse.
Dr. Jesse Reimink: Chris,
Chris Bolhuis: very difficult
question.
Dr. Jesse Reimink: I think it might be, I think it might be me.
Chris Bolhuis: Oh, please, [00:38:00] not true. Okay. I've seen more rocks and you know, as the saying goes, the best geologist is the, is the person that's seen the most rocks. So there we go.
Dr. Jesse Reimink: That's a good one. That actually is a, that is a famous line. Uh, and, uh, we, it's used a lot, especially in the, geological survey circle, so like up in Canada actually, and it's very true. The best geologist I ever met, a woman named Val Jackson. She mapped for like 45 years in the Canadian North every summer looking at [00:38:30] rocks all summer long, and she knew the most about rocks of any. I mean, it's absolutely fit the bill for that one. So I don't know if I'm willing to give up that crown to you, Chris, but it's a great and very reliable quote. All
Chris Bolhuis: All right. That's a wrap.
Dr. Jesse Reimink: peace.
