now on top of the global changes right that's just overarching through the whole world we also have local tectonic processes okay so this is all about relative sea level um what i mean by this is hey one of these ways that we can look at sea level is here right an active plate margin in california our land is slowly rising up so a person that may claim that sea level is not rising and that global warming isn't a thing um which would probably say hey check it out uh in this area we can see that sea level has actually decreased what they're using is the fact that the land is rising up sea level isn't decreasing okay their land is moving up so now you know one of the ways in which they're manipulating the science to effectively communicate what they want their message to be okay this is why i need you to be critical thinkers this is why the world could be a better place and everyone could understand each other more if we all educate ourselves which is what you are doing right that's what being a college student is is educating yourself to be able to think critically i'm not saying one way is right or the other i just want you to be able to think through it all okay hopefully you get some sort of ability to think critically through all of these topics so active plate margin that would cause um land to slowly lift up therefore causing a relative sea level change that would be going down it makes it look like sea level is going down another way that you could have things to look different would be if you loaded a plate with a bunch of ice that's actually going to push that plate down right therefore making sea level look like it's rising um relative to what the land is so maybe global sea level changes aren't happening at the current time and therefore all this ice you're pushing that plate down and it makes sea level look like it's rising up hopefully you understand that this is all kind of like analogy would be you take a a big ice cube and you jump on that ice cube you're going to push that ice cube down and it's going to make it look like the water is rising on either side that would be like ice loading okay a tectonic plate but then if you jumped off of the ice cube and the ice cube rose it would make it look like the water around it would be slowly but surely decreasing right or lowering that would be like an active plate margin and everything rising back up okay a delta can do the same thing as this ice loading as well as volcanism right it can actually load a plate and put so much weight on it that it will make it sink down or subside causing relative sea level changes that are increasing okay so let's take a look at that okay in the north atlantic coast at acadia national park in maine we actually got something that looks like sea level is lowering okay relative sea level is lowering how come because of glacial rebounds so this whole area used to be covered in ice and now that ice is gone it's melted away and it takes a very long time for this plate this huge tectonic plate to slowly rise back up to where it sits in the mantle and has its it's in isostatic equilibrium okay isostatic equilibrium is a topic that we talk about with regard to loading a plate with ice or loading it with a delta and pushing it down and then um finding equilibrium in that area okay and then slowly but surely ripping that away and it'll rise back up so this is the idea you add a bunch of ice onto a tectonic plate you're going to cause substance in an area and if you remove all that weight you're actually going to cause uplift it just happens over very slow periods of time and look at how the mantle is finding equilibrium right it's flowing out of the way for the substance and now it's flowing back into the area as it's uplifting or rebounding here's another idea of it right here's all that glacial ice causing a bunch of crustal subsidence here and then if that melts away we end up with crustal rebound and it's going to rise back up this would make sea level look like it's rising this would make sea level look like it's lowering if you got questions let me know email me okay so this is what the world look like 20 000 years ago during our last glacial maximum look at that look at all that ice up here ice here ice through this area as well in south america a bunch of ice right now there's not much ice left right so this area like hudson bay and stuff is slowly rising up all this area that used to be covered in ice right this whole area that used to be covered in ice is experiencing glacial rebound which therefore makes it look like sea level is actually lowering right which would be a great piece of evidence for somebody that's trying to combat the idea of global warming or sea level rise all right so features in shorelines let's just talk a little bit about a couple of these questions okay i want you this might be something to ask you on a test right can you put an a a g or a p next to each one of these numbers right so we've talked about all these this is from this lecture as well as last lecture can you tell me where you would find these things right marine terraces drown river valleys barrier islands emergent coasts sea stacks and arches delta's glacial rebound we just talked about the atlantic and the gulf coast last lecture we talked a lot about the pacific at the beginning of this lecture we talked about the pacific so try and do that you could pause it here okay there you go this is what you got marine terraces we talked about that that's in the pacific right those are those spots where a giant could sit on his bench or use it as a staircase right drowned river valleys that's in the atlantic that's because that sea level is rising right barrier islands those are both in the atlantic and the gulf the gulf is where we've got all those sea turtles um atlantic you could think about um okra coqui right um we also got emergent coasts meaning the coast is rising up okay that's in the pacific because of our active margin with the san andreas fault and all those faults i showed you from last lecture uh sea stacks and arch is common that's the pacific again you could see all of those at sunset cliffs which happens to be open currently you could go take a look um deltas we saw that video that happens that happens in the gulf why there's no waves right the gulf has very few waves i mean they do get waves from time to time but it's rare okay and then glacial rebound we just talked about that's in the atlantic we got that going on all right so that's the coastlines at all three of these locations all right what is the purpose of hard stabilization can you answer this one is it to decelerate coastal winds uh nothing to do with winds right is it to increase biodiversity along the coast well i'll tell you right now it doesn't increase the biodiversity along the coast all right see to protect the coast from erosion uh yeah yeah that's exactly i mean that's what we were talking about right is it it's a socio-economic thing as well but it does save homes if you have the money to build it right and then to be used as an alternative to growing fields well growing fields are a part of hard starvalization so don't get confused there it's to protect the coast from erosion but you know the whole story now okay now was an alternative to hard stabilization uh would it be a sea wall break water the use of rip wrap or beach nourishment well if i look at um the lecture i would see that well all this hard stabilization a sea wall is hard stabilization a break water is hard stabilization use of riprap that's what you use to make a sea wall or break water or a jetty or a groin so all of these are hard stabilization so d beach nourishment exactly i know you know it i know you know it alright that's the end of the chapter i hope that you are doing really well um and i look forward to the rest of this semester um let's finish strong