so from here i want you to focus in on wave refraction okay so this can be a bit of a tough thing to uh understand um but what's happening is is if you look out here these these are this is deep water waves okay these waves are traveling at the original speed in deep water and they're making their way from the left-hand side of your screen to the right-hand side of your screen okay and here's the shoreline now remember if there's a cliff here you're not going to want to set up your towel everything next to the cliff right you're going to be out here closer to the water now as you move towards shore you end up starting to turn into a shallow water wave right so you've got a deep water wave changing into a shallow water wave have you ever noticed that when you go to the beach you only see waves generally speaking moving straight into shore it looks like they're all just making their way straight into shore it doesn't seem like they're really coming from the left or to the right yet when i show you where our storms are originating with these way or where our waves are originating with these storms it's always in the north pacific or the south pacific and maybe even hurricanes but it always seems like waves are just coming straight in from the west that's because of refraction so these deep water waves start feeling the bottom turning into shallow water waves and what occurs is since they feel shallow water they start to slow down so that slow down makes them bend okay and this deep water part is actually still moving fast so it starts to accelerate this way and bend towards the coast right so once you are there at the beach looking out into the ocean you're really just seeing waves moving in directly straight in like they're coming from the west if you're on the coast of california but really this would be a swell coming from the north if you were sitting here looking out to sea this would be to the north this would be to the south so this would be a northwest swell yet it looks like it's coming in straight parallel to the beach so it's all because of these transitions between deep water waves and shallow water waves and the big thing to remember here is that waves bend towards shallow water so let's take a look at um once again uh one of the videos that keith meldahl my personal uh oceanography teacher when i was at miracosta college and uh he'll explain this in his own words and hopefully uh between me and him you'll understand a bit more about wave refraction so let's go there okay one of the things we're going to be doing in lab is looking at what's called refraction which is the bending of waves and they're changing direction as they come into shallow water near shore you may know that waves as waves move toward the shore they create an orbital motion in the water and that orbital motion dies out to nothing at a depth that we call the wave base and that depth is equal to one half of the wavelength of the wave and so when waves come into water shallower than their wave base they begin to feel the bottom that orbital motion rushes against the bottom and the waves begin to slow down and that causes the waves to slow down and bend and change direction which is the essence of refraction for example in this animation you can see the waves in deep water are approaching straight but they're going to slow down in the shallow water near the headland here but still go fast in the deep water and the bays on both sides and that causes the waves to bend and wrap and conform somewhat to the shoreline that's what refraction is and one of the things that's interesting about refraction is it's responsible for creating a lot of the famous surfing breaks that we see in southern california and elsewhere for example this is ring con point up near ventura and the swells are approaching here straight from the pacific ocean but they're slowing down in the shallow water near the point but still going fast in the deep water out here and that causes the waves to bend around so by the time they reach here you can see the waves changed its direction by about 90 degrees so that's extreme refraction and it creates a tremendous right break that's a famous surf spot at rincon here's another example these two little islands out near hawaii the waves are coming in from up here and they're approaching the islands and i've drawn the wave crests you can see them a little bit better and look at what happens as these straight waves approach the islands they slow down and drag in the shallow water near the islands but they're still going fast in the deep channels away from the islands and so they change from straight to rather radically bent that's refraction one of the things you'll be doing in lab is drawing what are called refraction diagrams which is your prediction of how waves will bend and change direction as they come into different shapes of coastline and so it's like you're up in an airplane and we give you the starting waves here in deep water and your job is to predict to draw the wave crests showing how you think they're going to bend and refract as they approach the shallow water you're always going to show them slowing down the closer you are to land where the water's shallower but going faster where the water's deeper probably the easiest rule to remember is the waves tend to conform to the shape of the coastline not completely but they tend to wrap to the shape of the coastline well one of the interesting things about and you oh by the way this picture here is a pretty good model to see where the land bulges out like this that looks a lot like rincon doesn't it so you can see it happens in real life right there okay one of the um neat things about refraction is that it can cause waves to bend their energy into one spot to make particularly large waves and a lot of famous surfing waves are created this way if a wave approaches the land straight like the like the hand here its energy is going to be spread out evenly across the coast but if refraction causes the wave to bend concave in the direction that it's traveling like the curved hand here it's going to cause it to focus its energy into one spot and that's going to tend to make a really big wave in just one spot this is shown in this diagram here where you can see an underwater ridge these contour lines show an underwater ridge so it's shallower water here and deeper water here and here and as these swells approach they're going to slow down over that ridge but go faster over here and that's going to tend to focus the energy right over the ridge and create a big wave right there where that x is and this is the kind of situation we see at a lot of famous surfing spots for example this spot some of you may recognize if you know about surfing waves is jaws or piahee in north shore maui and a very large wave forms here just in one spot um during certain northwest swells it's a classic what's called an a-frame where the wave just pops up in the center and is low on both sides so it's kind of like the letter a and um the reason for that is that the waves wrap to an underwater oh yeah here's laird hamilton on the on the jaws on the piahi way um the waves wrap to an underwater ridge it's shallow out here in this area but it's deep over to the sides and that means the waves start out straight but they get more and more bent more and more concave and that focuses their energy into the spot right over the ridge giving you both a left and a right break right over that ridge great so hopefully that helped out um let's take another uh example i know that you just saw this but let's look also at at this one right so for instance you've got um deep water waves out here making their way towards shore right and this is a big headland kind of like point la jolla say so this headland here is going to be shallower further out to sea right so this this uh headland is actually going to create shallower water out here versus at the base it's going to be shallow here but it's going to drop off deeper and deeper so the way that the bottom would look is that it's similar to what the headland looks like right to what the actual coastline looks like so what's occurring here is that the waves are actually feeling the bottom here slowing down a little bit initially here right in front of the headland because the shallower water is here and if you look off to the right or to the left these waves out here the same wave in this location or in this location haven't felt the bottom yet so they're still moving at their original deep water wave speed where this one's starting to slow down because that wave base is starting to feel the bottom since it's feeling the bottom it slows down and makes this refraction it's bending all the way right see that bend and then it actually gets more exaggerated the further you get closer and closer towards the shoreline so in essence at the end of it or at the beginning the beginning all the waves are moving in a straight line nice and parallel but once they get to shore and they feel all those changes in the shallowness or depth of the sea floor they bend and form to exactly what the coastline would look like at the very end of it right see how this looks just like the coastline and here it's a little bit less like the coastline and a little bit less and a little bit less until it's perfectly parallel that's exactly what's occurring it's changing slowly but surely to mimic the coastline now another thing i want you to take from this is that when we talked about point la jolla and we were talking about sediments right we showed that out at point la jolla you found bigger sand grains but then at scripps beach you actually found smaller sand grains because of lack of wave energy what we have here is this point of land here this headland is drawing in wave energy making it um erode away at the coast quicker larger sand grains would be found here right and then this is actually going to be losing swell energy so the bigger waves would be found out here because it's focusing in the waves and then the smaller waves would be found in the bay therefore leading to these big beaches of small sand it's almost as if this would be a summertime beach and this would be a wintertime beach but all at the same season just because of the way the coastline is shaped i hope that makes sense if not please email me like always right