now when it comes to barrier islands and hurricanes uh this is one way in which that speed at which this migration is occurring gets increased exponentially so here we are on this is in north carolina okay i don't know if any of you are from north carolina you know this area a lot better than i do um here's your barrier island out here and we're going to talk a little bit later about ocracoke i've been told that it's called ocracoke but i could be wrong i don't know what the pronunciation of it is but here's the path of this hurricane okay so this is hurricane isabel and it hits north carolina and it makes its way right through the barrier island so let's take a look at what this part of the barrier island would look like okay as well as the isabel inlet and isabelle beach check it out this is the impacts of this hurricane okay it ripped out this whole portion okay and it deposited it back here guess what happens that is a quicker migration than it was gonna happen over time so therefore these hurricanes actually increase the rate at which these barrier islands are making their way inland last semester i had a couple friends that actually had not friends with students and friends right you're all my friends i mean that's kind of how i was feeling before we all got stuck in this position but you know i'm hoping that we're all friends anyway um this whole area a lot of people end up with these four wheel drive atvs because they got to go over this kind of stuff to get to places um with supplies so this is a really interesting picture uh if you ask me of how a hurricane can actually increase the rate at which these barrier islands are moving and causing new inlets right in itself so another fun-filled fact about barrier islands here we are in palmico sound okay so here's paul miko's sound here's a close-up of palmiko's sound and we've got the oregon inlet over here this is cape hatteras out here and then here's okra cokey again and there's a interesting story here um i don't know if you ever heard of yeah this is the direction of the longshore drift um but i don't know if you've ever heard about blackbeard right he was an actual pirate guy right so blackbeard he's been made famous in some movies but he was an actual pirate um and what he found is that because that there are these limited inlets what he would do is he would hang out because they knew that ship shipping uh shipping industry is going to bring things in through these inlets and deliver them to the mainland well because it's this small area he would use that as his way to be able to steal a lot of those shipments right and then make a lot of money therefore he's a pirate just thought i'd give you some context into blackbeard just for fun okay okay now we're getting into the gulf coast that was the east coast let's talk about the gulf coast for a second okay so here i want you to focus on this padre island national seashore okay so here's padre island right here it's a very unique area because it has very high salinity lagoon so if you look here what's the average salinity of the of the water yeah hopefully you know that if you don't you might want to go back right go back make sure you know that it's it's an important thing to keep into consideration so if you look at the salinity here look at this this is over 50 parts per thousand it's insane how salty that is right so it has a lot of things have a hard time living here which leads to a very nice area for creatures to live on this area right along this barrier island so that nothing can get to them so what do we have we have the kemp's ridley right sea turtle this is one of the five threatened and endangered sea turtle species in padre island national seashore and this uh sea this national seashore here at padre island hosts actually five of the world's seven sea turtles okay so this area very important you wouldn't even know what's there it's this long skinny thing but it's all because of this very salty lagoon back here we're very very few predators can live and they can actually survive out there and have a nice home to stay all right another thing about the gulf coast we're going to talk a little bit about deltas and if you remember anything about what i talked about deltas it's the fact that deltas right they form where there are very little where there's little wave activity so if you take a look right this is this this section here it's cut off just a little bit but this is you know a huge uh area right i mean tens 20s maybe 30 miles 40 miles 50 miles across it's huge okay so this is a giant delta okay this is the river coming through and the mississippi river delta here's the river here it's compaction of sediments causes this whole zone right because it's slowly but surely subsiding it's adding more and more material causing so much weight on the plate that it's actually making the whole plate sink down or subside remember substance means sinking so the this is all happening because there's a very small tidal range in this area and there's very low wave energy so let's talk a little bit about deltas and why they occur and why they don't i'm going to let you take a look at this video once again it goes into the any audi belly button analogy so take a look the world is divided into two kinds of people those with any belly buttons and those with audis rivers also have innies and outies not belly buttons but mouths where rivers flow into the sea the land either pokes out or bends inward but rivers don't have umbilical cords so why do they have innies and audis well coasts are the front lines between two opposing forces land and water in order for the ocean to invade the land sea level either has to come up or the land has to sink down or be eroded away and in order for the land to advance into the ocean sea level either has to drop or the land has to build or be lifted up obviously if sea level drops and then rises back again there's no net gain on either side but things get more complicated when a river joins the battle for example during the last ice age sea levels fell by over 120 meters and rivers cut deeper and deeper valleys to reach the falling seas then about 18 000 years ago warming temperatures began to melt the ice and the now rising seas flooded river valleys around the world creating giant estuaries and giving us the any riddled coastlines we have today but when the steady landward march of the seas finally began to slow about 7000 years ago the coastlines around the mouths of some rivers began to gain back some ground the key factor was the sediments that rivers drop as their current slow at the entrance to the sea where the sediment supply was big enough and the ocean was calm enough the dropped dirt piled up eventually forming new land that both lengthened the river and divided it in two dirt would continue to drop out and build up at the mouths of both channels splitting the river again and again and again creating a new lobe of land advancing slowly into the sea thus the world's great audi river mouths the fertile deltas like the nile and the yangtze that have helped foster human civilization since its birth all came into being at just about the same time the same can't be said for all of the world's audi belly buttons what can be said though is that innies and audis for both rivers and people are a small record of how we came to be okay so hopefully you liked that video and now you know how estuaries and deltas form right and um once again deltas equals pretty much no waves therefore i haven't seen many deltas in my life isn't it amazing that all of these deltas right they formed right around 7 000 years ago did you see that part of the video i hope you did and what that leads to is a talk in global changes in sea level okay or you static changes in sea level global and eu static mean the same thing right when it comes to sea level so the ice volume in the world it changes up to 120 meters so about 400 feet okay so if you've got an ice age then sea level goes down 400 feet because all that ocean water is locked up in ice the opposite is true if you melt all the ice away then sea level will rise worldwide about 400 feet that's how much ice that's how much water gets locked up in ice okay our last glacial maximum this x-axis is thousands of years before present so here's present day we got 10 000 years ago 20 30 000 years ago and then this is sea level um and this is present level right at zero okay because we don't have much ice in the world right now so twenty thousand years ago approximately we were about 120 meters or 400 feet below what we are today and that would really change the scheme of what the coastline look like now another thing to think about when it comes to changes in sea level is that there's thermal expansion and contraction of seawater so as temperatures rise water actually expands and this contributes a larger percentage not a larger percentage but a very significant percentage of sea level rise this thermal expansion okay as water temperatures continue to get warmer and warmer sea level will actually get larger or taller and taller okay um also changes in seafloor spreading rates that can contribute so all three of these i need you to know as to why global sea level changes okay ice volume thermal expansion and contraction of seawater and changes in seafloor spreading rates changes in seafloor spreading rates is an interesting one um if you have a fast spreading ridge at a divergent plate right so we're talking about mid-ocean ridges if it's spreading really fast that means you have a lot of heat underneath you have a large magma chamber that large magma chamber actually lifts up the sea floor in that area therefore displacing the water around the world leading to increased sea levels does that make sense it's almost as if you had a bathtub and you marked where the water was on the side of the bathtub and then at the bottom you decided to place a large say a large substance like let's say like a bunch of bricks it's because they sink and they sit at the bottom so if you put a bunch of bricks at the bottom and you looked at your current sea level or the bathtub now it would be above the mark right because you displaced that water well this is the same idea except it's just the bottom of the bathtub or the bottom of the sea floor rising up a little bit okay and therefore causing a change in sea level so c4 spreading rates so the faster it's spreading the larger the magma chamber the more that sea level on the bottom uh would push the sea floor up causing sea level to rise