hey everyone let's go over chapter eight waves and water dynamics [Music] when blowing across the surface of the ocean generates most waves uh we call this a disturbing force okay so atmospheric circulation uh transfers about two percent of the energy towards the surface of the ocean and that's what generates these wind-blown waves so but anytime you have an interface of fluids with different densities that can also or their interaction can generate waves as well so uh when we have the air ocean interface that would be like as if you're on a boat on the surface of the ocean the atmosphere and the ocean are in contact that's the interface ocean waves are generated right you can have atmospheric waves so giant air masses uh with different densities kind of uh making their way uh in the atmosphere can generate atmospheric waves that affects our day-to-day weather and then um inside of the ocean so think of below the surface there are also large masses of ocean water with varying density and when those masses of ocean water with differences in density interact with one another on their interface that generates internal waves internal waves are associated with if we go back remember the picnic line okay so there's a low density surficial or surface water that kind of sits on the surface of the ocean and down to about 100 meters um that's the surface mixed zone that's where most uh wind generated waves are created below that then you run into the peak neckline okay um so here actually you have an image right here you can see this here so here's the low density water sitting on top of the higher density water okay so when you have fluids with different densities this is their uh interface of you know exchange where uh one sits on top of another and this is where internal waves can be created and that's associated with the peak nuclei remember that's the ocean layer where you have the rapid uh changing density with depth okay these waves are huge okay now here are your surface waves generated on the surface of the ocean these are your internal waves internal waves can be really big they're much larger than surface waves think of the best way to think of internal waves have you ever seen a desktop ocean where it's kind of like this rectangular um kind of pivoting uh container that contains two liquids one blue one white and it sloshes back and forth and it shows you kind of waves bouncing off back and forth from the surface or like a lava lamp okay lava lamp has a number of liquids of different densities with different colors um being heated up and so it kind of moves around within the vessel that's the interaction those are the waves that are created some of these internal waves can get as large as 100 meters which is 330 feet so think of a wave the size of 33 basketball hoops stacked on top of each other that's pretty big tides or turbidity currents even large ships passing through certain areas can generate internal waves and internal waves can be hazardous for submarines if say you have a submarine deep underwater at depth right and if it gets swept up by a wave that's kind of passing through that area at that depth it can actually push the submarine or kind of pull it down to depths and pressures that the submarine can't withstand and then it gets crushed essentially and many submarines have been lost in this fashion okay so waves one of the best ways to think to think about waves is simply just energy transferring through a medium okay medium being like a substance right and that substance in this case is the ocean the ocean is uh a massive area filled with salt water okay and energy's passing through that medium that's essentially what a wave is and the water particles in the ocean are the result or their motion is the result of transferring that energy to the next particle next to it and then that energy kind of traverses through the medium as it uh goes along its way okay so the particles in the ocean as energy is kind of moving through it can either move up and down back and forth or in orbital fashion so like circular fashion around and around this graph here on the right shows us the kind of global distribution of energy in ocean waves so these are the different types of ocean waves with a varying wave periods we'll talk about what that is in a second but most wind genera generated waves occur uh in within this range okay and then this is the average amount of wave energy uh that's produced per year essentially so there are a lot of wind generated waves that that produces the most energy rate right around here tsunamis earthquake volcanic landslides those are waves which with much long period times okay but they still have um they occur infrequently but they um release a lot of energy okay into the ocean water and then ocean tides are are more like as predictable and um they occur at specific times every 12 to 24 hours i guess depending on where you are um but it's either once or twice daily uh and these are the the two peaks of energy um for that type of wave okay here are the principal causes for these different types of waves here's the gravitational pull of moon and sun which we'll talk about in the next lecture and then really what generates most waves on the surface of the ocean is the wind progressive waves oscillate uniformly and they kind of progress through the water without breaking there are three types longitudinal traverse and orbital longitudinal the best example of this is compression and expansion okay um much like hands clamping uh clapping or thumping on a table um this transmits energy and then uh like when you clap you're compressing air between your palms of your hands and then you make that kind of clap sound and as this type of wave passes through the medium whether it be air or whether it be the water the water molecules will compress and expand a transverse wave the best way to kind of visualize this one is imagine you're at the gym and you see one of those guys doing that like rope exercise where it's like tied to the wall and they're like swinging it up and down screaming loudly yeah that workout is like a transverse wave so it has this kind of s shape where it makes particles move kind of up and down okay and then orbital waves are where water particles move um in a circular fashion so they don't look really travel very far they just kind of bob up and down and that's the kind of direction of the the water molecules as the wave passes through it okay and that's one thing to understand is that um again thinking uh waves kind of moving their wind generated waves moving their way through the ocean they don't take the water along with it with that ride they just kind of transfer that energy to the next water molecule and so the water molecules found here just kind of move in a circular fashion and they kind of remain in a similar spot to where they were beforehand longitudinal waves like i said they're also called push-pull waves they compress and expand okay um think of uh a coiled spring or i don't know if you guys know what a slinky is uh but a slinky if you attach it to a wall and give it like a hadouken right it'll compress and expand and that would travel along the slinky to the wall and then reflect back to you okay longitudinal waves are pretty cool they can travel through any medium solids liquids or even gases transverse waves those are the side to side workout waves with the rope energy travels at right angles to the moving particles so these only transmit through solids and not through liquids and then orbital waves uh the best example of these are waves on the ocean surface where you have the orbital circular movement of the water particles all right let's go through some wave terminology um so you can kind of understand it here's a cross section uh this is the ocean surface okay and then this is the ocean at depth okay so it's kind of like a little cross section the crest of the wave is the top of the wave here so if you're floating out in the water and then you hit you kind of bob upwards and you feel like the highest peak of a wave that's passing by you that's the crest the trough is the lowest part of the wave that's down here okay so this is the crest and this is the trough of the wave um the still water level is a kind of like a theoretical level where as if the ocean had zero energy passing through it the water would lay still at this level it's typically halfway between the crest and trough so it's also called the zero energy level the wave height is the distance between the crest and the trough so that would be right here you can see it here this distance wave height okay to the crest and from the trough and then the wavelength is the distance between the one crest all the way to the next crest that would be the one wavelength okay uh we talked about the stillwater level i don't know why it's repeated here um but here this shows you see these circles here this all shows you the orbital path of the water as the wave kind of as the energy passes through the medium here and the reason why these orbital circles are larger here is because there's more energy moving those particles closer to the surface as as these water particles move okay they'll move the particles below them where the ones below them also move in that orbital fashion but if you notice the circles are smaller that represents the amount of energy diminishes the deeper and deeper you go okay and we call this here the wave base the wave base is essentially the distance from the surface to which water particles are affected by the wave energy okay the the steepness of a wave um that's uh defined as the height of the wave so from trough to crest divided by the wavelength and then there's this magical ratio the one-seventh ratio okay so um if you have if the wave steepness is greater than one-seventh so meaning that if the height is larger than 1 7 the wavelength the wave will break okay so you'll have rough seas and then you'll have a wave that starts to have like white caps at the top of it okay terrible drawing but those are white caps i guess okay all right i mentioned the wave period the wave period this is uh the in time or t that's the time for one wavelength okay so crest to crest to pass a fixed point so think of it as you're anchored on a boat in the open ocean and a wave hits the side of the boat right it's the amount of seconds it takes for the next wave crest to strike the boat or like if you're at a pier and you're standing on the edge of the pier it could be anywhere once a wave strikes the pier then the next crest of the wave hitting that pier you could determine the wave period okay and that's important because um that lets you know how much uh or how you can use that to find out wave speed um and and it's also important for i guess surfers as well uh care about this kind of information so that they can kind of time to ride the best wave from an incoming swell wave frequency is the inverse of uh the wave period or one over the wave period that's what the inverse is and what that essentially means is just asking you in a fixed amount of time let's say you say a minute right how many wave crests will pass by that fixed location per unit time in this case we'll say a minute so you you know every wave crest that strikes the pier you count how many times it happens in a certain given unit of time that's the wave frequency right that's how often are waves frequenting your area essentially um here are the this is an explanation of the wave base okay the wave base which is right here is highlighted in green that's the extent to which the energy from the wave that's moving in this direction interacts with the water molecules in the ocean so it's a depth from the surface okay and what's pretty cool is that the wave base can be calculated based on the wavelength right l is the wavelength right so say your wavelength is 10 feet that means the wave base is 5 feet okay that means that wave will interact with particles 5 feet beneath the surface okay beyond five feet below the wave base wave base uh those ocean water particles are unaffected okay so when waves kind of pass through a given area the water particles move in a circle okay so it's really just the wave form or the energy that travels forward and it leaves behind the water molecules as it kind of goes through and this is best kind of shown via the rubber duckies let's say you were taking a bath and you created some you know massive waves in your bathtub the rubber ducky if you look at its like um as it's floating in the water as a wave kind of passes through it now the wave moves in this direction the the duck will kind of ride up to the crest of the wave hit the crest and then fall back down as the wave continues to move forward and if you track its path you can see that it moves in an orbital pattern much like the water molecules that are interacting with that wave so the wave energy advances and move moves forward ultimately many waves as you well know because most of us whenever we go to the ocean we don't actually go way out into the open ocean we're either in the coastal waters or on the beach that's where the wave energy is dispersed is when waves crash onto land okay so there's the wave base that's the orbital movement of the water particles stop and so if you have water depth that is greater than the wave base okay so remember say you have a 10 foot a wave with 10 feet wavelength right which means its wave base is 5 feet okay so if you're in very shallow water right and if it's um deeper than five feet then that wave would be considered a deep water wave okay because that wave is passing passing through the ocean and not affecting uh or not being affected by the friction of the bottom of the sea floor so we refer to those as deep water waves all right so all j wind generated waves in the open ocean are deep water waves why because our ocean is very deep on average and and the the energy that's uh that's kind of moving air masses above the ocean cannot transfer enough energy uh into the ocean to create um shallow water waves that shallow water waves are the other type of waves so essentially all wind generated waves even if it's like a category five hurricane blowing winds whipping winds back and forth through a huge area if it's in the open ocean it's going to be a deep water wave where there's negligible water movement below half the wavelength of the waves being generated okay the wave speed which in this case should be called solarity which is used with the c indication that is the wavelength divided by the wave period okay and you can use this really handy dandy chart to determine [Music] the solarity of a wave if you know um uh essentially just one thing if you know the wavelength um okay so this line here uh is the are the wave periods in seconds now this is an ideal situations in the open ocean so if you're in coastal waters they may not make the same because coastal waters are shallower so those waves might interact with the ocean bottom and actually slow down so it's not the same but if you're in the open ocean and if you're able to calculate the wavelength in meters let's say you calculated a hundred meters so you just draw a straight line up until it intersects this graph here and so the wave period is eight and because the wave period is eight you can now draw a line straight across this graph and calculate the wave speed in meters per second so somewhere around 12 or 13 meters per second with a wave with a wavelength of 100 meters and that's true for anything you just go straight up where it intersects and you go across and that's the wave speed in meters per second [Music] shallow water waves on the other hand this is when the wave depth or d is less than one twentieth uh the uh wave length so essentially what's happening here is the quote-unquote water feels the sea floor okay so these are are big waves that kind of will pass through the entire depth of the ocean and under those circumstances to calculate the solarity or velocity of the wave we use a different equation okay so that's shown here but this shows you how shallow water waves interact with ocean water notice that the orbital these are orbital paths of the water but notice that they're kind of flattened downwards and that's because of the interaction of these water molecules with the ocean floor so essentially the ocean floor interferes with the orbital motion and it causes them to be flattened so some shallow water waves that would be the case for wind-generated waves in shallow areas okay tsunamis okay the uh are tides and then um those are examples of shallow water waves that would make as they kind of move through areas of the ocean they would interact with the water that way okay so how are wind generated well waves developed well they initially start off as capillary waves think of you're holding let's say your morning cup of coffee and it's a little too hot so you blow on the surface to cool it down a bit you're essentially creating wind generated capillary waves in your coffee okay so the wind generates stress on the sea surface and i'll show you in the next image but you create v-shaped troughs okay low-lying areas of the wave and the wavelengths are really small okay less than one point centimeters okay that's like uh 0.7 inches so smaller than an inch okay once uh like say the wind continues to blow stronger and stronger and for longer periods of time these capillary waves will their wavelengths more and more energy will be transferred to these uh small waves that they'll get larger and then they become gravity waves okay so once the wavelength exceeds 1.74 centimeters then you have increased wave energy and now you get pointed crests and then the rounded truss instead of the v-shaped traps like this you get the rounded troughs okay so here's an image showing you the area where you have capillary waves but if you have wind continually blows for longer periods of time transferring that energy then you'll get gravity waves and the reason why they're they're called gravity waves is because see if i were to draw the still water level i know that's hard to do because these waves are kind of small so what happens is uh the water or as the waves traveling through the water um it hits a height that's high enough that when um the wave kind of comes down to its trough it passes the still water level and gravity aids in that because the force of gravity pulls that water downwards and it pulls it past the still water level and then it adds energy to it so that the wave continues to move forward or the waveform continues to move forward so that's why it's called the gravity wave this gravity is kind of aiding in the kind of transfer of this energy through the water okay so yeah think of capillary waves as ripples in a pond you throw up you just kind of throw a pebble into a pond and you see ripples kind of just radiate outwards okay um and then uh when we refer to as the sea that's there's a lot of meanings to this but um the sea is an area where wind driven waves are generated so out in the open ocean we've got prevailing winds like the trade winds or the westerlies or the polar easterlies right those prevailing winds are blowing across the surface of the ocean that's where wind driven waves would be generated and that area is also called a sea area okay so some of the factors that affect wave energy obviously wind speed right if you have higher velocity winds that's more and more energy that's going to be transferred to the surface of the ocean generating those waves if you have wind duration that's long meaning like prevailing winds or sustained winds at high velocities that's going to even add more energy to the surface of the ocean and then the fetch that's defined as the distance over which the wind blows okay so in this image here this is a storm so we've got something atmospheric going on here the prevailing winds are blowing in this direction okay the fetch is the area in which those sustained winds at high velocity are blowing over the the sea right and that is critical in terms of developing really strong waves okay and so a lot of times with storms like this a lot of the larger high energy waves move faster than the storm itself so the waves begin to advance ahead of the storm and that creates a swell okay and that's where um you see this here uh all these uh longer wavelength waves moving ahead of a storm and that's what creates a swell and that's why surfers like a lot of times especially here in florida when there's an approaching hurricane or a low pressure system or some sort of storm surfers often will go to the ocean um hour or i mean like half a day or a day before the storm arrives because that's when the increased or larger waves will be arriving on the coastline it's kind of an indication of a storm coming so they like to surf that especially here in florida because a lot of the waves here aren't surfable let's say or so when there is a storm there's added energy so it makes for better waves okay the the wave height is directly related to the wave energy meaning that if you have like taller waves obviously then you'll have more energy associated with that wave front but most waves are are typically less than about 2 meters which is 6.6 feet but if they break if you see waves break especially in the open ocean we call those white caps and and that's uh when those ocean when they break uh that means the waves steepness has exceeded uh one seventh the wave height versus the wave length okay that's typically when you'd see white caps then there's the the beaufort wind scale and that describes uh what the appearance of the sea surface would be like in situations where you have a storm or a lot of wind blowing in page 258 of your book they show you with pictures what hurricane wind speed and the open ocean would look like if you were out there this is a satellite image of wave heights globally and if you look at blue areas or purple areas um these are areas with wave heights that are kind of small okay so uh you can see that all here pacific ocean close to the equator wave heights in in the red um here are in uh five five to six meters okay um so those are really big waves and so you can see that over here if you notice in the southern hemisphere we've talked about this area before the circumpolar currents remember there's not much land down at these latitudes in the southern hemisphere this is the area here where there's some land at these latitudes but these currents kind of encircle the entire globe unimpeded so they can just keep going and there's prevailing westerlies that blow in this direction so that contributes to the kind of really high wave heights here so these are really dangerous areas to be in the open ocean at these latitudes [Music] here's the beaufort windscale you can see that in your book as well it actually has pictures in the book which is which is very helpful but you can reference that in case you wanted to see what uh what being in the open ocean would be like if you're under hurricane conditions so with wind speed in excess of 73 miles an hour sustained winds the air would be filled with foam and spray c completely white and driving spray visibility greatly reduced you don't want to be out in the middle of the ocean during the storm okay so there used to be kind of a theoretical maximum uh to what what scientists used to think the largest waves could possibly be and they thought that waves couldn't exceed 60 feet although that 60-foot rule was kind of proved wrong by the uss ramapo okay they in 1933 they observed out in the open ocean a 500 foot approximately that long ship caught waves are estimated that it had been through waves that were 112 feet high so almost twice that 60 foot rule which is incredible the way they measured that was the captains at the bridge of the ship their eye level uh was right at the crest of this wave and so they knew that the bridge down towards the trough or the stern of the ship was about 112 feet so that kind of proved a lot of people wrong about that 60 foot rule and the reason for this is is because certain areas of the ocean have these enormous waves because of special conditions kind of like what we see in the southern ocean in the southern hemisphere and what that kind of leads to is the understanding of of a fully developed sea okay um that's an area of the ocean where for a given wind speed um it it's the minimum amount of fetch and duration of the wind where the waves cannot grow any larger essentially this is a picture of the us ramapo after it had gone through this rough sea which was actually it was a typhoon in the pacific and this is an aircraft carrier so this is reinforced steel that was bent uh down downwards i'm sorry not this is not the uss ramapo the uss ramapo was undamaged other ones like this is the bennington in 1945. this uh went through a typhoon and this is the damage from it so the ocean um those waves and the energy passing through the ocean can be extremely strong and what's what's really crazy um is that in the ocean uh approximately 10 large ships like container ships or big tanker ships are lost at sea without a trace every year about ten just boom disappeared combination of of uh the ocean being so big and inaccessible as these ships are so far away from being able to communicate uh with anybody but the fact that uh the ocean can have storms and waves and and waves generate not necessarily when there are major storms but that just can completely overtake a really large craft which is pretty crazy so here's the third that fully developed c term that i was that i was talking about essentially is waves can't grow any further in a fully developed sea because they'll lose as much energy breaking uh they'll pass that one-seventh rule and get too high up and they'll start white-capping under the force of gravity um and so they they kind of they can't grow any further so it's really like an equilibrium condition and when you have a storm or a fully developed sea out in front of it you'll generate a swell those are uniform or symmetrical waves that travel outward in front of a stormy area and the waves that move through here have the fastest velocity so they have really long wavelengths and long crests and that helps transport energy from the storm and the prevailing winds out long distances to areas that are unaffected by the storm at least temporarily okay here are the are the different variables for a fully developed sea essentially it's showing you the different conditions necessary to create a fully developed sea which is something you don't want to be into if you're on a cruise ship or any other vessel you would not want to be in an area that has become a fully developed sea where the waves are at their maximum uh height [Music] so so these are different conditions increasing wind speed increasing fetch the duration of the wind speed the average height of the waves itself and the wave period okay swells so they're longer wavelengths those waves travel faster and out distance other waves so typically with a storm you'll have a swell arrive on the coastline with waves with really long wavelengths okay so the frequency is a little bit longer like also fewer waves hit a fixed point at a certain amount of time and then once the swell passes and the storm arrives you get more of uh choppy wave action all right and swells are are usually created by what we refer to as a wave train now this is an ideal scenario as if a swell was moving in undisturbed sea but what a wave train is essentially a group of waves with similar characteristics and they they're moving in the same direction and so what happens is as the wave train moves into an undisturbed area of the ocean the initial wave will die out the leading wave we'll call it wave one will die out and then wave two becomes the leading wave but then a new wave behind it will form okay um and so uh obviously this is energy um being transferred into a uh an energy energy less area of an undisturbed ocean so there's a little bit of energy loss and drop in velocity as the wave train kind of moves through the undisturbed area but it's an interesting way of how waves kind of travel through the ocean and create an ocean that's disturbed and full of energy when it didn't have any okay so basically the waves are dispersing that energy as they're moving through okay and then the decay distance is the distance over which waves can change from choppy to a uniform swell okay so what happens is the wave train speed is slower half the speed of one of the individual leading waves so here it is this is the wave train here's wave one so you have four waves okay moving through an undisturbed part of the ocean so if you notice one wave one dies out but then behind wave 5 wave 6 emerges not as energetic as the first wave but it emerges and now you still have four waves moving through the area wave 2 dies out and it kind of repeats itself okay [Music] this this is under ideal conditions i mean in the ocean in reality if there's a swell kind of moving through an area there might be another swell moving in an opposite door area so opposite direction and then some coastal currents that affect the wave trains interacting with one another so it's a bit more complex okay and that's what leads us to wave interference patterns this is when you have waves coming in from different directions and how they interact with one another it's essentially a collision of energy and when you have uh two or more systems interacting with one another there's that kind of collision and you can have two things occur or three things really well many things can occur but these are some of the things you can have constructive interference and that's when two swells or waves that are in phase kind of run into each other so they have very similar wavelengths and so then what happens is it's this option up here so you have two waves that that hit each other and they're in phase but the result is you'll have constructive interference meaning that the wave heights will get larger and the wavelengths will get larger as well so this generates stronger wave action um when they just happen to be synchronized okay um but you can also have destructive interference and destructive interference are when you have waves that are out of phase and they essentially cancel each other out so here you go here you have um this one looks like the the wave frequencies a little lower than this one here right they're out of phase so when they collide and interact with one another they actually cancel each other out and the ocean becomes calmer as a result okay but in reality it's not so simple as destructive and constructive essentially what's happening is that they're both occurring at the same time so what you get is a mixed interface okay so what you'll have is waves approaching in in phase and out of phase and every once in a while they'll be in phase creating a constructive interference and a very large wave and other times you'll have just choppy waves as they kind of cancel each other out so we call that mixed interference and this is what it looks like here so just imagine here you can see waves coming in at different angles swells coming into different angles and then you get this choppy pattern right here so here's sea surface height which is kind of big it's kind of flat and then you see kind of big constructive interference nothing and then a huge constructive interference wave right there and then it goes back to the normal over here so that's mixed interference where you have two swells two or more swells with different wavelengths kind of moving in and if you notice sometimes when these swells kind of move in and the waves are in phase you'll get something a huge change in sea surface height okay we call those rogue waves those are massive mostly spontaneous solitary ocean waves that occur in the ocean open open ocean and they reach really high heights and they they can essentially sink a lot of ships going back to um you know 10 tanker or container ships container ships like those giant ships that carry uh shipped goods from different parts of the countries for trade those are 40 foot containers and they have hundreds of them on the boat those things are lost let's see about 10 globally disappear without a trace which is crazy it makes you think twice about going into the open ocean because a rogue wave could just occur at any at any time even though the odds are pretty low i think the the calculated odds of running into a catastrophic roadway rogue wave or one in one one in uh 1200 okay i'm sorry one in three hundred thousand uh running into one of those monstrous rogue waves and that was the basis of that the perfect storm uh story i don't know if you saw the movie with um was it george clooney and uh marky mark yeah that's right mark wahlberg right um that was apparently a rogue wave that that sunk their vessel but other luxury liners like the michelangelo was damaged in 1966 from these destructive powerful waves here's an image of that of the michelangelo and this crashes through some storm waves in the north atlantic you can see the damage that occurred on the ship this was pretty intense so rogue waves are really spontaneous and random they're very difficult to forecast it's just known by shipping companies and people who navigate out in the open ocean they know that this can happen but scientists have kind of narrowed down areas where it's more likely to happen than not and that means that they can occur near weather fronts or downwind of islands is where they see that these rogue waves occur more often and if you have strong ocean currents kind of like the ocean currents we're talking about that are around 40 to 60 degrees latitude in the southern ocean those are areas where you could have roadways occur more often all right so let's talk about waves in the surf zone means waves as they approach land okay the surf zone is the zone where waves are breaking near shore okay the reason why this occurs is because you have shoaling water and that means that the water becomes gradually more and more shallow as ocean water approaches land right so deep water waves when they encounter shoaling water that's less than half their wavelength meaning the bottom of their wave base then they start they change from deep water waves into transitional waves and so as waves approach the shore these are the things that that occur the wave speed decreases and that's because the water is interacting with the bottom of the sea floor okay the wavelength decreases kind of like you're compressing uh an accordion so to speak as the wavelength kind of decreases and the the waves kind of scrunch up together a little bit as a result of the the interaction with the sea floor the wave height increases so the wave kind of uh kind of grow upwards in height and when this occurs then the wave steepness increases and when the steepness exceeds that magical ratio 1 7 the wavelength the wave will break and you're familiar with this right breaking waves in the surf zone i'm sure you've been caught up and tumbled around a few times when you've been on been at the beach but here it is so here's the wave base right so here's a deep water wave but then as soon as it starts feeling the bottom changes start to occur okay so the wave energy or waveform is moving in this direction orbital pass but here it starts interacting with the bottom of the sea floor but if so if you notice the water here starts to slow down because of that friction and then the wave kind of tilts forward and as it tilts forward the wave height increases and as it tilts forward the wave height increases steepness increases and then the wave starts to break all the while as soon as the it hits uh the sea floor the velocity decreases so that's what happens when waves approach the shoreline and so that creates three types of breakers spilling plunging and surging and you get these three different types of ways that waves break based on the sea floor essentially um spilling breakers this is where you have ocean that's gently sloping and so what happens here the wave energy is expended over a long distance because it's been interacting with the sea floor so these just kind of break up and just don't really curl as much the water slides the down the front slope of the wave itself not really great for surfing plunging breakers are where the sea floor has more steepness to it moderate steepness these are ideal for kind of curling waves so what happens is the wave steepness it kind of is is much higher and the wave is kind of tilted forward so then it curls over a pocket of air and that's when um surfers love that because i i got my first two bro because they kind of um follow that ride the kind of energy and the wave form as it curls through and they go through those tubes so that's that's best for surfers you have that curling wave crest and that wave energy that's approaching the shoreline is expended over shorter distance and that results in that curving one then there's surging breakers and this happens when you have very steep seafloor and here the energy is spread over the shortest distance and you get good body surfing waves because it's very close to shallow water but not great for surfing uh because essentially the water crashes into the sand directly so uh the waves just break onshore i'm sure many of you have experienced with this all right so surfing is a really crazy sport i don't do it um but i've seen a lot of surfers on the beaches on the east coast west coast not as much um but it's really like riding a gravity operated water sled so to speak you're kind of you're the surfboard is buoyant right so it floats on top of the water um but then you're also uh kind of riding the force of gravity down the wave and you're balancing that kind of buoyancy of the surfboard plus the gravity and surfers really skilled surfers can hit speeds of 25 miles an hour and that's why it's it's such a thrill some really massive waves can be generated i think in the beginning of the chapter they talk about an area in portugal where you see the largest waves form which uh under really crazy conditions once once in a generation man um i'm i'm quoting my inner point break here but uh the world record holders for that those crazy surfers will ride waves they're over 80 feet in height which is insane because if they fall um they're going to be smashed and pushed around by that water and many of them actually died uh or drowned from as a result of interacting with water with that much energy in it okay so ever noticed how you've ever been to the beach that the waves kind of crashed directly in front of you there's a reason for that waves rarely approach a shore at a 90 degree angle so what happens as waves approach the shore they bend okay and then they bend until they're near nearly parallel to the shore so when waves approach a coastline they're rarely like just coming straight at the coastline they usually come in at an angle and then a portion of the wave feels the sea floor first and that slows down that portion of the wave and so then the other side of the wave moves faster until it also hits the seafloor and it slows down and so that causes the wave to kind of bend towards the shoreline okay so different segments of the wave travel at different speeds because of that interaction so here if you notice look the waves are really traveling in this direction right and here's where you would be i'm hanging out it's fun throw the football around right but when you're standing right here the waves are crashing right in front of you and the reason is right here this dash line is where the waves start touching the sea floor and as it does this portion of the wave will slow down but this portion will speed up as a result and when that happens that means it's kind of turning in this direction right so these waves kind of slowly turn and then start facing uh the shoreline we call that wave refraction and it just has to do with portions of the wave kind of velocity slowing down and essentially what happens is the wave starts bending towards the coastline and so what this means is that wave energy is unevenly distributed along the shoreline certain areas of the shoreline will have a lot of wave energy concentrated towards it i know this is not the case in florida we don't have rocky shorelines like this but say on the west coast of the united states california they have a lot of rocky shorelines and so when waves approach the coastline these waves will start interacting with the headlands of a coastline first and then all the wave energy is directed here it'll cause erosion break up these rocks and then the wave energy kind of dies down in these cove areas here and this is where you see the deposition of sand so a lot of the coastlines on the west coast will have nice little coves where people can recreationally enjoy the beach and then these kind of cliffs and headlands that take the brunt of the wave action and storms okay so the take-home message here is more energy is released at the headlands and then energies dissipated into the bays so here's just that angle of showing you how waves incoming waves that are coming in in this direction will bend around the coastline and still crash directly in front of you if you were right here okay so these headlands will erode away because they're receiving most of the wave energy and then over here the wave action dies down and you actually have a lot of sediment accumulating in these areas um another cool example of wave refraction and i've seen this if you go to new smyrna beach there's a lot of um surfers that take advantage of of this we call this the wedge but in the inlet there there's a jetty that kind of sticks out and so what happens is when you have incoming waves okay here's an incoming wave um here's the jetty right so that incoming wave will hit the jetty and reflect off of it and then these the and then intersect with the ink another the same incoming wave here and then create larger wave heights in this area here in this wedge area here um it's wedge shape so that's where surfers take advantage of this kind of constructive interference it's pretty dangerous because look how close they are to the jetty you want to go crashing into those rocks but this surfer has taken advantage of the increased wave height from this wedge and it makes it for ideal um excuse me ideal surfing conditions then there are standing waves this is a different type of wave where two waves with the same wavelength are moving in opposite directions this can happen in enclosed basins and particles uh let's say in this closed basin or like a lake kind of slosh back and forth uh think of like water in a bathtub you have a fixed amount of water and it sloshes up and down um so the water particles on each end of the basin will move up and down um let me show you what that looks like so here um you'll have water move down as kind of all the water moves to the other side of the basin we call this an antinode okay the node's in the center and it's essentially motionless so it just kind of swings back and forth like a see-saw here's the maximum water flow and then back to motionless so this just kind of repeats itself as a standing water wave kind of progressive progresses back and forth from each side of the basin then there are tsunamis tsunamis are incredible incredibly dangerous these are seismic sea waves so they originate from earthquakes and sudden seafloor movements of tectonic plates earthquakes are the most common cause of tsunamis but there are other causes there can be underwater landslides remember the continental slope area right off the kind of off a continental margin there can be a massive landslide and a lot of debris kind of goes crashing down into the abyssal plain that can generate a seismic wave volcanoes when they erupt the edifices are very unstable and a whole sector of a volcano can collapse into the ocean that can cause a tsunami a massive underwater eruption uh there's been some major eruptions in the past krakatoa um as one example in 1883 generated a massive uh tsunami from the from that eruption and then also meteorite impacts can create large waves as well so tsunamis um occur earthquakes are very frequent some of these other ones aren't as frequent but tsunamis can be generated in a number of fashions but tsunamis are have very long wavelengths over 125 miles okay and so they behave as shallow water waves right because if you take half of this distance which would be what 62 miles that's way uh larger than the depth of the deepest parts of the ocean so um these waves when generated it it encompasses the entire water column and affects all the water in the ocean if you're in the open ocean and a tsunami passes underneath you you might not even notice it it passes very fast um some speeds are of about 300 uh miles an hour um and they move through the open ocean where tsunamis get dangerous is when they approach the coastline okay so here here's an example of the sea floor we have two tectonic plates kind of moving against each other and then one of them will move above the other and one of them kind of moves down and when this happens when this whole plate moves upwards think of it as like you're in a kiddie pool and a community pool and you're just using your arm and just thrusting huge waves at like a bunch of children that are in the pool right and you're just like sending these giant waves to them that's how that's essentially how they're generated these giant tectonic plates are just kind of moving forward thousands of kilometers generating these huge waves um and so uh and then the trouble exists once these waves approach um a coastline okay so uh let's say there's a uh like the one in when was it 2003 in sumatra this will generate a wave and then it'll propagate outwards uh in all directions and then that tsunami will hit places surrounding say sri lanka thailand and cause a lot of damage they move at really fast speeds you can fall into the rabbit hole of crazy tsunami destruction on youtube if you just google tsunami in sumatra or in japan i have crazy footage of incoming tsunami seismic waves just inundating the area and it's not it's not like the movies a lot of times in the movies it's like this giant wave height you know up like uh 40 stories high they're huge they can be up to 40 meters or 131 feet but most of the time it's kind of like a sheet of water that comes in and just floods the entire area so low-lying areas like this would suffer tremendously loss of life people drowning because they're getting caught up in this very fast moving water hit debris and drown gets swept away and a lot of loss of property as well some uh the tsunamis mostly occur in the pacific and the reason for this is the pacific ring of fire has a lot of convergent plate boundaries where there's a lot of tectonic plates kind of um pushing against each other and uh and that's what generates tsunamis in addition to that there are a lot of volcanoes surrounding these areas so a lot of earthquakes and volcanoes lead to these kind of catastrophic events loss of human life really it damages a lot of the coastal areas here's an example in hawaii about 25 million dollars in damage and 159 deaths in 1946 as a result of a tsunami uh a crocodile as i mentioned was a volcano in indonesia that erupted and created a a absolutely massive tsunami um there was another one 1946 in hawaii uh when there was an earthquake off the aleutian trench which are those volcanic islands kind of off the coast of alaska in papua new guinea in 1998 there was one but most notably and when [Music] kind of tsunamis hit the kind of or were sensationalized by our kind of modern media was uh 2004 that's when it was in sumatra let's see i think i see it here 2004 yeah box day this was the day after christmas at like 9 00 a.m um an earthquake hit um and so that's over here you can't really see there it is sumatra on the other side but this this tsunami propagated outwards and affected india southeast asia and a lot of people died from this one fatalities um 300 000 people okay i don't know if you know but like the orlando and greater area has a population of about 280 000 so imagine everyone in in the orlando and cities surrounding orlando uh perishing as a result of one catastrophic event one wave well it was a series of waves but anyways a magnitude 9.2 earthquake one of the strongest in human history struck uh this area off the coast of uh sumatra so about 1200 kilometers of sea floor moved between two tectonic plates so that basically just pushed a lot of sea water and generated that tsunami this one was the the deadliest one coastal villages in this area of of the world um really suffered because there are a lot of low-lying coastal villages really close to the water um i urge you i can't do this but you can watch these um youtube videos to get a sense of what the tsunami destruction was like another um uh let's see okay so yeah the tsunami that indian ocean uh tsunami the indian ocean is also kind of like a smaller ocean in comparison to the pacific so you have less time to warn people of incoming tsunami but now we have a system of buoys to warn countries after this event which is pretty crazy but it traveled more than 5000 kilometers its wavelength was about 300 miles an estimation of 230 to 300 000 people died in 11 different countries okay so you can watch that video so you could spend half an hour watching different crazy uh videos but here here's just an example of how catastrophic this was here's a low-lying area a town a before and after satellite image of absolute tropical paradise to um nothing there everything being swept away uh it's really tragic another notable tsunami was the um tohoku earthquake tsunami which was march 11 2011 okay that was a magnitude 9 earthquake off the coast of japan in the japan trench this one was the most expensive it affected a lot of japanese towns the initial surge was 49 feet and a lot of these harbor um tsunami walls were toppled over and amplified the local topography a lot of places were flooded watch this video this shows crazy waves coming into the japanese coastline and decimating towns i think here about 20 000 people died and it also i don't know if you remember but the fukushima nuclear power plant which is kind of close to the coastline was inundated by the tsunami and that caused the reactors to melt down and then there was a whole issue with radioactivity in the surrounding areas so it was a big problem in japan and they're still they're still slowly cleaning out the fukushima uh power plant area from its uh meltdown in 2011. still an ongoing issue but since then we've developed a pretty good tsunami warning system uh the pacific tsunami warning center in honolulu hawaii uses seismic waves to forecast tsunamis so after an earthquake occurs they quickly work with the results to try to predict if the tsunami will be generated but then they have a series of buoys a system of buoys that's part of the deep ocean assessment and reporting of tsunami or dart don't touch my dart um and this detects tsunamis passing through a buoy and then that way you can warn people in coastal areas of an of an impending tsunami now the way to get away from tsunami is essentially just go uphill um you have to get to higher ground and when you get to higher ground the the water will reach a certain level and then it'll go back away i mean it'll leave your entire village or house completely destroyed but at least you have your life right most important but that's the way to get away and if you're ever vacationing in any areas where there could be a tsunami one of the telltale signs obviously if there's an earthquake if you feel an earthquake a tsunami could be approaching sometimes it could take five to twenty to half an hour or a couple of hours depending on how far away the earthquake was or uh whatever the the variables are but if there's an earthquake start to find an evacuation route to go uphill um if you if you're by the beach and you see the ocean start being drawn out like it's a really massive low tide you need to get out there fast because that means the water is getting kind of pulled out into the ocean and then it's going to come raging back in okay so this is the tsunami watches is issued for for areas that when there's an earthquake then they'll warn people here are the buoys and they can detect [Music] seismic tsunami waves kind of passing through the area so they they move ships from the harbors most scenarios you do have a lot of time to prepare for an incoming tsunami there's only few times where it's a map it's a matter of minutes okay but but it could be a matter of minutes so you have to take it seriously okay and finally waves can be used as a source of energy there's a lot of energy associated with waves essentially it's just wave energy waveform moving through the water um and uh so essentially but there are a lot of challenges to this because most uh most of the waves that give off a lot of energy or could trans potentially transfer a lot of energy come from storms so you know it's difficult to protect power plants from the storms and um because storms are not uh you know like sustained or continuous um to produce power consistently could be an issue some environmental issues if you build them too close to the shore they can interfere with life and also sediment moving up and down the shoreline here's an example of one okay so you have incoming wave and that oscillation of the wave column will push the air in here and make this turbine spin and that's what generates electricity so they can be as part of a coastline like this again they're they're kind of expensive to maintain they can break down pretty easily because they're getting hit by waves every single day right but it's a way of generating renewable energy so it should be explored the first commercial wave plant was began operating the year 2000 the limpet 500 that was a land installed marine powered energy transformer off the coast of scotland and it generates 500 kilowatts of power under ideal conditions all right this one was a wave farm in portugal created in 2008 and it essentially just kind of sits here in the water and it generates about 50 wave power development projects globally with this new idea so people are exploring this because it's kind of like a an endless amount of energy as just you know wind will always kind of blow on the ocean surface and then that will push waves and that energy can be transformed into electricity but here's a global map showing you the ideal areas where a lot of energy could be generated um and you know some areas are pretty close to land so that can be helpful uh in generating energy but again it can be very expensive and it's sometimes difficult uh um to you know connect electricity to these distant areas and then efficiently transport that generated electricity to cities that need it