



S1: and that last question th- i know i told the T-A to, be really easy on the on the terrains question. you know that very last one. 
S2: i have a question [S1: sure ] about the um, the one question um, where we had to find the coordinates of the Atlantic Ocean. if we have the longitude and latitude mixed up 
S1: oh that's a small [S2: just one point off. ] yeah. i mean i think the total, [S2: just the right numbers. ] for that question was something like five points. [S2: oh okay. ] and uh (four was implicitly suited for) 
S1: what?
S3: is this, is that a mistake?
S1: thirty-two points?
S3: yeah. 
S1: like a mistype doesn't it. probably meant three, so <LAUGH> 
S3: it was one of the ones i didn't know and i was like, uh'oh. 
S1: i didn't catch that. <LAUGH> 
S4: are the tests graded yet? 
S1: they're graded but i haven't checked over with 'em yet. uh, i d- i wanna do that before i hand 'em back.
S4: and are they curved? are you gonna curve? 
S1: oh yeah. well, i never know what people mean when they say curved you know. 
S4: adjusted to the rest of the class? 
S1: yeah, it's a_ yes. that's true. but i- it's not to the extent that i say okay, Gaussian distribution tells me that the- there's there's a, thirty, thirty-two percent, one standard deviation, above and below the means. 
S4: curves always should push up grades. they should never bring 'em down. 
S1: i beg your pardon? 
S4: curves should always push up grades (and help those who are on the edge) 
S1: that's right. [S4: (good) ] pretty hard to, do it that way yeah. it's uh... generally what i do, and this is why it's hard to, say what the final grades are gonna be, uh till you actually do the averaging, now i put the, B-C boundary somewhere, near the median. but what i always do is look for, breaks in the distribution cuz there's never a perfect, Gaussian distribution. so i try to put, put uh, the letter boundaries, where there's a little, little gap. so that there's not, a lot of, people affected by this boundary problem. and then by having the extra points available always it's always for that for those one or two people that are, close to the boundary, it gives them a chance to hop over it. 
S4: are we having a quiz today? 
S1: yeah. actually. <SS LAUGH> we wouldn't want you to get out of shape. <LAUGH> it's a real short one uh, multiple choice. real easy. 
S5: the last one was multiple choice too, but it was, twelve, multiple choices. [S1: <LAUGH> that's right. ] is this a real multiple choice? 
S1: well this is only three. you got a better shot at this one. 
S6: is it based on the reading or the notes? 
S1: the reading. you did do the reading? right? 
S6: (i didn't want to) 
S1: <LAUGH> it'll it's comparatively easy... and remember it doesn't count against you. just a chance to, make some points. 
S4: it counts against you if everybody else gets it right. 
S1: yeah, well. if everybody else is right i mean, the letter grades are determined before i add in the points so it doesn't_ it's not a competitive, sort of thing. the tests are competitive. but, but not the actual points. <P :11> i, i wanna talk a little bit about the movie before we start on the other thing. and uh 
S7: it needs a better plot. 
S1: pardon? 
S7: it needs a better plot. it needs a better plot. 
S1: it needs a better plot yeah. well it's too it was too, this way and that, right? well they were that's, one of the reasons i wanna go over it. is there were a couple of key points, made that i wanna emphasize. uh for instance. now we it focused primarily_ it told you there was a lot of geochemistry going on. but it really didn't, go into great detail there. they just said it's it's cool stuff. and it's building these big, polymetallic sulfide chimneys, that are... if it was cheap to get 'em, <LAUGH> and get 'em back they might even be economically important. but it's not. so, if you go by the_ just say, okay geochemistry is interesting it's building these big chimneys, there are sulfide deposits, fine. now the, geology and geophysics part, the w- guy that uh Ken McDonald, the chief scientist's husband, his his main point, was what? do you remember what he, he said about, exploring the deep and, all that sort of stuff? he showed that little model of what the area looked like. what [S6: miles ] was his main point? what? 
S7: if you can do fifty miles you can do the rest of it, pretty much. 
S1: you what? 
S7: if you did a fifty mile, stretch you can do the rest of the four thousand. 
S1: well he he said that was a very special area. that he could predict, that this was gonna be an active area just by, how it looked. you know it was, it was slowing up, it was uh higher than stuff around it. and there weren't any real central valleys in it it was just one big, warp, in the ridge. and so he predicted that this was gonna be an active area. so. this is_ being able to predict in science is a, is, one of the great things. being able_ that means you semi understand it. and, understanding is the ultimate goal. now from the biology point of view, they said several times in there, the fact that this same this whole community, first of all it was completely decimated, by this eruption of lava. they didn't know that that had happened but when they got there, the first time, it was decimated. wi- i i don't think they used this phrase but it was called the, the tube worm barbecue. i mean everything was <SOUND EFFECT> and then, what seemed to really, surprise them, was that within two and a bit years, everything was back. complete community the s- tube worms the, dandelions the crabs the fish de da de da de da. this whole community living off of bacteria, had completely reestablished itself. ninety percent. but what he didn't go into, was why was this surprising? 
SU-M: where did it come from also? 
S1: that's why it's surprising. where the hell did it come from? i mean these things are, except for the fish, which are following the, the uh, tube worms the tube worms don't, sorta hike up and march off you know. they're stuck there they're they're what we call benthic, organisms. they're screwed into the bottom. they're attached, to the rock. so how, the surprising thing, is how, did they get there? i mean... i mean this_ we're leaping way ahead in the course here because, oceanography's all tied up and it's hard to teach anything in a sequential order without jumping back and forth occasionally. and here we've leapt into the biology part of the course. but, it's a primary question. yes. 
S8: could it happen (in a series disaster don't they_ the) only thing i can think of is kinda, maybe how plants have seeds but i don't know if 
S1: that's not a bad idea. she's talking about seeds well, i mean we talk about the dan- dandelion for instance right? i mean we knew how the dandelion reproduces. affects our lawn and even they've got it, what they call an analogy in the, in the film. dandelion puts out seeds that, are picked up by, the wind, and blow to your neighbor's lawn. that's how it works. and so, your suggestion i take it is that the, these organisms must do something similar. the logical_ anything it i- i- unlike dandelions, where, they reproduce by, putting out these, seed floaters, uh but if you've ever, done the battle with dandelions you know that it's also, uh they have roots that will just, if you don't get 'em out will just, regenerate, no matter what. now tube worms don't have that advantage. they don't have any roots. you, you wipe those guys out and they're gone unless they re- in e- in essence reseed. and so that, is really the, the working hypothesis that there is some s- sort of way of, reinfecting, this area. and if you think about it this is a, this is a interesting process here. here we are in the di- deep ocean, with this long linear feature, where there are, hydrothermal springs spaced out, at some distance apart. sort of like little oasises(sic) in the desert. spewing out hot water and bacteria that can, form the base of the food chain, the organisms that other organisms eat. and somehow, these other organisms the ones that feed on the bacteria find, these hot springs, and colonize them, in a, in two years... and that's, really what is surprising. because, our vision of the deep sea is a place that is, dark, cold, and relatively still. it's not like thinking about the dandelions where, a good strong wind like, we've had in the past, few days i understand, can pick those things up and spread 'em all over the place. in the deep ocean we think about currents, in general, being very slow. you re- you remember the films, you saw the the bacterial snow, it was coming down very gently right? there wasn't like it was <SOUND EFFECT> in a blizzard, a a current. so, whatever motion's down there is not real fast motion... well i i'm not claiming uh that they know everything about the biology but, your hypothesis, that somehow, these benthic organisms are, just throwing seeds, little s- eggs and gametes and, immature organisms out into the water, and hope that some, portion of 'em, land in a place that's suitable. not on the asphalt not on the sidewalk, but on somebody else's lawn. that is a that is a a a biological strategy, for recolonizing, places or just colonizing places that are suitable. and you think about that that's, that's terribly inefficient. i mean that means that if you're gonna be really successful you've gotta produce one hell of a lot of seeds. and then you've gotta be prepared to keep those things coming. because any moment, your colony may be wiped out. but you can infect or establish another colony. interesting problem. now that's one of the reasons it was so surprising it was trying to find out, i mean and they still, have not totally worked this out. for instance they don't, know for sure how long, how much variation there is in, the age of a particular colony. how long will one last? i mean that was one of the th- questions they left unanswered. will it be here next year? or the year after. in the same place or will it, everything quiet down, the spring sort of die back, and the supply of food diminish, and the colony sort of, die off? it's one of these questions we really, are still investigating. very expensive, to go down there and look for these things. they can't do it year after year after year. any other questions about the movie? what'd you think of it? did you like it? should i show it again next time? yeah i, i sorta liked it. there's so much covered in it though it's real worth talking about it. geology geophysics predictability at the ridge crests what's going on. geochemistry that you can actually see the, the development of these uh, chimneys and the water, spewing out. uh, the metal oxides and iron and manganese mainly, uh turning the smokers black in places. and then all that biology. yeah. 
S4: what was the temperature inside that? the smoker or whatever. 
S1: the- they said it was three hundred fifty degrees centigrade. 
S4: why doesn't that boil? i mean
S1: why doesn't it boil? [S4: yeah. ] it's sort o- it's because of the tremendous pressure, down there you know when you i- you ever been camping at at high, altitude? and you know how, it's really hard to get the damn thing to, water to boil? [S4: yeah ] well it'll boil at a lower temperature because the pressure's lower, but the the heat conduction is, is not as good either. so, down there, under those pressures, the water has to be a lot hotter to really, vaporize, to overcome the pressure, problem. it doesn't usually happen. and there's some, there's a tremendous amount of debate a- as to what, the up- upper limit of temperature in which bacteria can live. the conventional wisdom right now is somewhere around a hundred and twenty degrees centigrade. um, but, not being a biologist and not being, constrained by, conventional wisdom, um, it's not gonna surprise me if they come back in a few years and say well we found 'em at a hundred and fifty or two hundred. i mean i don't think there's anything magic about a hundred and twenty frankly. anyway. speculation. now what we've uh, what we were c- covering, after we finished the, sort of plate tectonics which, is a tremendous... subject and i could spend the whole course on it but of course they won't let me do that, if i'm teaching, introductory oceanography. take out a piece of paper put, your name on it real quick, and you've got, exactly one minute, to give me an answer to a three-part multiple choice, question. <P :08> y'all ready? okay. of the three basic types of_ oops i didn't, deep sea sediments or, sediments of the deep ocean, which accumulates accumulates most slowly on the sea floor. which type, accumulates most slowly in general. now they discuss, examples of each of this in each of these types in your reading. the uh biogenous sediment which comes from the skeleton skeletal material of organims- isms that live in the deep sea, the terrigenous sediment that comes off, of uh land, one way or another, and the hydrogenous sediment, that is sediment that is actually precipitated from sea water as a chemical precipitant. and occurs not just at ridge crests but, throughout, many parts of the oceans. okay go. one minute. <P :21> all you need to write is your name, I-D number, and either A B or C or you can, write the whole word out if you want. <P :32>
S9: is that it or? were you joking about the six-part thing?
S1: i'm sorry? 
S9: were you serious about the six-part thing (or not?) 
S1: well i mean there's, three choices. that's what i meant. 
S9: but at first you said we had a six-part multiple choices. 
S1: no three-part i meant to_ just, three choices. 
S9: i thought it had six different questions. 
S1: no no no this is just one question. three choices. okay pass 'em over. <P :07> i'll do the best i can. <P :07> why don't you (give it) that way. let me get it over here. i already got yours? 
SU-F: yep. 
S1: have i got everyone's? one more over there. (i'll just) run around... okay that's everybody's the answer is... A. hydrogenous. some of these uh, manganese nodules and such accumulate at uh, you know a millimeter per thousand years it's very very slow. we'll go over that in lecture. <P :07> okay... sediments of the oceans. now why, before we, go into distribution and names and stuff like that, you remember, when we were talking about plate tectonics that one of the, interesting things about the sediments of the ocean when we started figuring out how thick they were, was that they weren't very thick. and so the oceans, could only have been accumulating sediment over a relatively short period of time... and so therefore the ocean basins had to be young compared to the continents. but these sediments, they come from the land they come from the ocean, they're blown in by the winds they're carried by currents... and they're laid down on the sea floor, layer by layer by layer by layer, and always, i mean this, <LAUGH> is a, a big principle of geology is the oldest stuff is always on the bottom. i mean this is, pretty self-evident. but, it's uh called the Law of Superposition. it means, stuff on top is younger than stuff underneath. not hard to, not hard to buy. but all this stuff coming in see is, is it's it's like a record. it's keeping track, of what was coming off the continents what was coming down from the ocean what was coming out of the atmosphere, as time, went, by, ever so slowly. it's a, a way of exploring the past is to look at these sediments. so when we, talk about the various types of sediments and how fast they accumulate, you can s- sort of translate that into thinking well now what could i learn from these sediments? if they're coming down very slowly that means m- my time resolution is gonna not be very high because that means, each millimeter only, uh represents a thousand years... it's gonna be hard to get much detail, out of that record. but if it's coming down fast, so that each millimeter represents a few years, then you can, get a lot of detail. so let's, look at the various types. <P :06> and first by, by source, and these are the ones we talked about, this is a fourth type here. not very important. but you have to include it to be complete. terrigenous s- stuff that's carried, to the oceans by rivers and and the wind, biogenous shells of organisms that live in the ocean, they die, and their shells fall to the sea floor, hydrogenous minerals that precipitate, on the sea floor, and then cosmogenous dust and stuff, from outer space. <P :05> pretty easy. now the other, way of classifying sediment is, where do they come from. uh where are they deposited. and so if they're deposited close to shore, they're called neritic and of course close to shore means close to continents and so most of that stuff is terrigenous, but it will have some biogenic components. that is, bits and pieces of things that were actually created by organisms. hemipelagic means sort of pelagic so let's just skip down to pelagic. pelagic, ar- i- the word pelagic is from the Greek and it means, of the oceans. and so this is where you have your biogen- biogenous oozes that is the, very fine-grained sediments composed of microfossils from, diatoms and, other, uh plants and animals that have shells. deep-sea clays which are the wind-borne dust and the hydrogenous sediments, and then hydrogenous crust and nodules. solid pieces, of uh chemical precipitants that formed in the ocean. hemipelagic, means a mix of terrigenous material and these other types of material... now here the varying, rates at which <BREAK IN RECORDING> here are the here are the rates at which things come down. on average. cl- the terrigenous stuff comes in various sizes all the way from very fine glain- grained clay all the way to sands, and it comes in at various rates. five centimeters which is about two inches, two inches, per thousand years, up to, a lot more than that. per thousand years. biogenous oozes generally, are one to two two centimeters per thousand years. but can get as high as ten centimeters per thousand years, in areas, that are very biologically productive. that is in which, it's_ the waters are rich, with planktonic organisms. and we'll s- see where those ar- areas are. and what they call red clay, come down at fractions of a centimeter per thousand years. red clay is, is just a s- mostly the s- hydrogenous and windblorn blown sediments. and the hydrogenous uh a millimeter or less. so the average is somewhere, from point-two to two centimeters per thousand years. that's not very fast. and so you can see, if it were say one centimeter per thousand years, somewhere in the middle there, if the oldest part of the ocean is like two hundred million years old, uh a thousand years is ten-to-the-third, a million is ten-to-the-sixth, so it'd be one times ten-to-the-third, centimeters thick, on the oldest part of the ocean. that's not very thick... so u- usually on the average you expect to f- find, a few hundred meters, of sediment. and that is indeed what you do find. now let's talk a little bit about, each of these types of sediment. and we'll start with the terrigenous, stuff. <P :09> it's very difficult... to carry sediment, out into the ocean very far. if you think about it, what happens? the the rivers flow down to the ocean right? in general in most places not every place but in most places, as you come down, from the mountains down through the hills down through the coastal plain, the level or the or the um, the steepness of the slope of the river gets lower and lower, and then when it hits the ocean, in a way it's like, hitting a s- a rock wall i mean that it can't go any deeper than that, and so the flow, stops, in terms of river flow. and other processes take over. currents, tidal flushing in and out, longshore currents, wave generated currents, things like that, will then take that sediment that's delivered by the rivers, and move it around a little bit. but it's hard to get it out, out, far into the ocean. so the terrigenous sediment just tends to pile up around the edges. unless it's carried by the winds. and, of course dust, in the in the atmosphere, can go a long long way. in fact, uh, people have traced dust storms uh via satellite, well clear across the Atlantic. they can pick up, Saharan dust, dust from the Sahara desert, in the uh Caribbean. over clear across the Atlantic in the, islands of the Caribbean. they can track dust sto- storms coming off of the Tibetan plateau easily to Hawaii. so this dust it may not be a lot of it and it may be very fine grained but it goes a long way. i'll show you some, patterns of its distribution later. so, terrigenous sediment dominate the nearshore areas where the rivers empty, and where there's no river near shore, then you get other stuff. you get carbonate reefs in tropical regions, because carbonate uh the reef growing, animals, don't like m- murky water they depend on sunlight, to, as part of their, plant animal interaction. and so they don't like muddy water, and they'll grow where there's not in tropical areas, where there's not a lot of, river water coming in. shell debris things like, clams and scallops and mussels and stuff like that. sea urchins. all sorts of, animals that live in the oceans, that produce hard shells, can accumulate, and actually, make sand and other debris like for instance the, the sand on the Bermuda islands a- a- any of you ever been to Bermuda? [SU-F: yes. ] nice place isn't it? [SU-F: yeah ] they're famous for their pink sand b- beaches and they're all made out of, shell fragments. Bermuda's an old, coral reef sticking up there, off of, North Carolina. and uh most and and it's, the weathering of the of the ancient corals and of the, various other mo- mollusk and sea shells, that actually creates the sand on those beaches. glacial debris, that's debris carried out by, mountain glaciers, such as those, in uh the Rockies that feed into, Canada, from Canada and Alaska into the Pacific, or from uh, Norway and Northern Canada into the, North Atlantic. they can j- they carry, terrigenous sediments, to the ocean but, once they get there you see it's it- they can go, a little bit further than the rivers cuz the ice doesn't melt right away. and it floats off into the ocean, drifts around the ocean until it melts and as it melts it gradually drops, the sediment that it's picked up along the way when it flo- flowed down the mountains and across the continent area... now a, couple of years ag- back i took a, took a cruise out of San Diego. headed for Hawaii. and just for the fun of it i measured, the maximum, sediment thickness as i headed away from, the coast, and plotted it up here for your, amusement. now, what it shows is, that when you're very close to shore... the sediment is comparatively thick, and then it's very_ it's uneven because remember there there're lots of sea mounts and ridges and fractures on it and stuff like that, it's uneven in it's distribution but i- every, set, bit of distance i would i would take another reading and then i plotted it up and you see a general, it's sort of an exponential decay. that it drops off rapidly at first and once we get about a thousand kilometers, out from shore, then it sort of flattens out. flattens out at about, maximum sediment thickness of only about, ten meters. even though, the crust here, close to shore is younger than the crust out here. in other words, the crust close to shore has been around a shorter of amount of time, than the, ocean crust that exists, two and a half or two thousand five hundred, kilometers offshore. so it's been there a long time, could have collected more sediment. but because it has always been far from, shore, it hasn't. it's actually collected less sediment. because all this terrigenous material just couldn't get out there. <P :20> this is a map, of uh, of a particular mineral, called quartz. you guys ever heard of quartz? yeah it's it's pretty common. it's what most beach sands are made out of. not Bermuda but. very resistant, makes these bur- beautiful clear crystals you know. see 'em for sale sometimes. very resistant to uh, chemical, weathering. uh very r- hard mineral. and it's a common, mineral, in, continental rocks but a very uncommon mineral, in the crustal rocks of the ocean. the crustal rocks of the oceans have a, very very different chemistry, and practically no quartz, in those crustal rocks. so if you go out into the sediments, of the ocean, and measure the amount of quartz, in those sediments, you're looking at stuff, that a- almost certainly came from the continents... so then if you s- if you do that and then look at look at it as a percent of the total sediment that is, a percentage of uh, quartz in the sediment on in terms of weight, then you see patterns, of, quartz, distribution, that are very far from, sort of even and they're very far from, from just exponential decay from the continents like i showed in total sediment thickness. and in general, here's what you see. you see, a big band across, the north, the northern oceans here, in the c- in the uh, North Pacific, and in the Atlantic. and these, this band of quartz is delivered, from the continents to the oceans, by the winds that blow from west, to east. picking up dust and taking it out over the ocean. here are the trade winds. they're blowing off, offshore from the east out into the ocean and the Pacific and they carry a little bit of, dust, that are, that is uh, dominantly quartz. and you see a similar sort of pattern, in the South Pacific but not as clear. here's the Saharan dust coming off the S- Sahara over here. this is off of Mexico this is off Peru, Ecuador. now you do see some river influences here. here's the Ganges Brahmaputra, flowing into the Bay of Bengal, carrying a lot of quartz from the Himalayas. here the_ some winds coming off the Arabian desert carrying quartz that way. so it's not all windblown some of it comes from rivers. but most of that, is windblown, material. so, right away you can think, well, if i go out there and sample, take a vertical, pipe, and drive it into the sediment, at some place... say i do it, out here... and i look, at the amount of quartz, and in the size of the quartz grains, back in time, what's that gonna tell me? <P :07> see i'm developing a history of quartz. now how would i interpret that? i've got, going down, the the sediment through the sediment back into time and i'll see, variation in both the relative amount of quartz, collecting at at time and, the size of the quartz grains themselves whether they're, very very small or just small. what would i, deduce from that? 
S5: would that give you a measure of the wind, direction and the strength over time? 
S1: direction and what? 
S5: the the, velocity or? 
S1: yeah. the size will give you an idea, of how vigorous the wind was. faster the wind the bigger the size. right away that tells you something about past climates. how how much, activity the wind had. now what would the abundance tell you? yes. 
S3: like if a continent_ how close was that spot to the continent, as the as it progressed because, because, when the continent was closer to that particular part of the, the sea, larger grains could get there because it was a shorter distance and then as, it moved away smaller grains could collect, [S1: mhm ] because they were carried by the wind. 
S1: it's all, very very logical, and um, but not quite right. n- no points off. <LAUGH> no it's a good idea. and if you just if you get very close to land it's absolutely right on. if you're within a thousand kilometers within that, band of where terrigenous sediments can come in by rivers too, what you say is correct that the, the size and the uh and the rate, is uh, very dependent on the vigor, of the stuff, and the proximity to a c- uh vigor of the transport and the proximity to continent. but if you get this far out out in the middle of the ocean, the dust that gets out that far has to be injected, very high up, into the atmosphere. and so by the time it starts going out, over the ocean, the the very coarse stuff falls out very fast. and so it's it it mixes in the atmosphere and has almost a constant grain size, of the finer end, except it is influenced by how vigorously it was thrown up to start with. so if there're big dust storms throwing lots of stuff up, you'll get a little coarser material, out here in the middle. now what about the abundance with time, what's that gonna tell you? if it's only, from the wind... you were close. what what we think it tells us, is that, the more dust you get, it must mean something about how arid, the source of that dust was. i mean if it was, lush forests, everywhere it's hard to get dust right? but if it's like a desert like the Gobi desert or something out there it's easy to get dust. and so the more dust in general, per unit time, you can think of it being the more arid, the climate. generally. there are some, exceptions to that but, in general, the size tells you about the vigor, and the relative rate at which it comes in tells you something about the aridity of the climate. <P :06> interesting thing about the dust record up here, is that, both the s- size and the accumulation rate, is very low up until about, eight million years ago. and then it kicks up, and goes back down again and then it, kicks up again about two and a half no about three and half four million years ago. and, this was very puzzling why it should do that. why there should be big changes. and what we think it is, is that, it's all tied up into the... how'd i get this thing on backwards? no wonder i couldn't tell what was going on. we think it has to do with the creation of the Tibetan plateau when, when uh India plowed into the southern Asia it lifted up, the Himalayas lifted up, the Tibetan plateau, and it created, all this high altitude, dry area behind the Himalayas. that just, generated the Gobi desert was created, and it was an area where you got lots of dust, and vigorous winds. and we'll come back to that when we talk about atmospheric circulation. but what we think that dust record is out here in the Nor- North Pacific, is a record of the development, of the Himalayan and Tibetan, plateau. so it's a history of, how plate tectonics the movements of continents, has changed climate. interesting history. <P :05> now here's a uh, figure from your, from your text. and it shows in a very general way, the distribution of, calcareous sediments. red clay, hydrogenous sediments, and silicious oozes. calcareous and silicious lets talk about for a minute here, these jargon terms again. anybody know what, silicious is? you know what does that, what does that mean. 
S6: silicate? 
S1: pardon? 
S6: silica or silicate? 
S1: yeah s- it's got silica in it. you know the element silica silicious, there are a lot of organisms that that sh- that live in the ocean, they live in lakes too for that matter but, that actually precipitate, S-I-O-two, sili- silica dioxide, as a shell. sometimes it's called opaline silica, because it doesn't have a real crystal structure. it's like glass. like window glass. it's no- window glass is not a crystal, it's S-I-O-two, that has cooled rapidly from a melt, of sand and a few other little chemicals, and created this perfectly clear pane, almost pure S-I-O-two, and organisms build their sh- shells, out of much the same material. calcareous. what does that, you know what the chemistry of that is? anyone who yes sir. 
SU-M: calcium. 
S1: calcium. primary, positive side of the, of the equation. it's calcium carbonate that is C-A, C-O-three. calcium carbonate and that's what you always see when you see a clam shell. or a, a mollusk of any type. what you see when you see coral reefs. there're a lot a lot of organisms that build their shells out of calcium carbonate. and there are a lot of organisms that are planktonic that is single cell floaters that just, live out in the upper layers of the ocean all over the world, and produce their little teeny, one millimeter and less sized shells, out of calcium carbonate. now if you look, at this distribution you'll see, there's a lot of calcium carbonate in the Atlantic. there's a little bit of red ca- clay. red clay is usually defined, where there's not much calcium carbonate and there's not much, bioge- biogenic silica, in the sediment, that's all that's left. so, calcium carbonate all over here, all over there, all over the South Pacific but not much in the North Pacific. we'll come back to this. mostly red clay there. now here th- look where the silicious oozes are. there's a bit up here, in the far North Pacific, and it dominates, the Antarctic region. <P :06> we're gonna explore, in the, next lecture, what controls these distributions. but let me just make, it clear about one thing. what this is, is it's telling you what the dominant sediment type is. it doesn't mean to say there's no biogenic silica, in this blue area, it's just that it's mostly, calcium carbonate. it doesn't say there's not any, clay, in this gray area, it's mostly silicious oo- oozes. so it's what dominates. that's what this map shows. now it also shows manganese nodules, which are hydrogenous, sediments. and they usually occur, where, sedi- because they precipitate very slowly, they usually occur in red clay areas, or on bare rock, where other things are, accumulating very slowly as well. it's hard for them to accumulate, if they get buried. so, it you usually find manganese nodules and other sorts of things, that are chemical precipitates like that hydro- uh, hydrogenous sediments, in areas of very low sediment, accumulation. <P :05> now let's, we've now covered the types of sediments and we'll come back to some of 'em in detail but let's start with the terrigenous sediment, first. and remember i said, that this sediment is carried, to the oceans by rivers. but what happens to it next, is, a very interesting part of oceanography... we're gonna talk about waves later on when we talk about physical oceanography, but you all know from going to the beach, that waves, are very energetic things. i mean they've got a lot of energy, associated with them. energy that can, erode beaches and cut into cliffs and carry houses away and, dump your boat upside down. so these are very active agents, in stirring up and eroding sediment. there're also currents, tidal currents in the oceans, moving, moving water, back and forth and anything that's suspended in that water, will go with it... and they will continue to move it about until, whatever's suspended settle out of suspension by gravity. now while the sediment, is in suspension... it actually adds its density to the density of water. and when you know the density of, rock, even in the finest particle clays, is, more than twice as dense as water so if you're adding this suspension of clay to, its density to the density of water you're really creating a fluid, that is denser, than water. muddy water is denser than, clean water. to put it in, very simple terms. so if that's true, then sediments in suspension, may actually flow, as a separate, dense, liquid. and we can observe that happening, uh especially during storms wh- which have, stirred up a lot of water, and a lot of sediment from the bottom, created this muddy water, and this mo- muddy water can flow out, across any- even the gentlest of slopes, across this the outer shelf, over the shelf edge down the slope and out onto the continental rise, as literally, turbid rivers, of water. it's, salt water, it's got clay in it, it's denser than the sea water around it, and it flows, as a separate fluid, carrying this sediment out. and that's how, much of this terre- terrigenous sediment, gets out so far. it can get out, up to about a thousand kilometers away, from the s- from the shore line, and much of this is through these turbid, flows. <P :08> now remember we_ i think earlier on, in these uh courses we talked about, sea level changes right? remember that? and how much did i say that uh sea level could change between a glacial interglacial period? you remember? it'll be on an exam so you better remember eventually. 
S10: could you say the question again? 
S1: huh? 
S10: what's the question again? 
S1: how when we ha- when we had an ice age, twenty thousand years ago how mu- and we took water out of the oceans and put it onto land to form these big ice sheets, how much of that removal of water, from the ocean onto the ice sheets will lower sea level? 
S10: sev- seventy meters? 
S1: Dave? 
SU-M: a hundred and twenty meters? 
S1: spot on. a hundred and twenty meters. right down to the shelf edge. remember? that was a_ that's where we brought it up. why is the shelf edge at, a hundred and thirty meters? well, it might have something to do with the fact that we lowered sea levels, down to a hundred and twenty meters, thirty, uh twenty to a thirty thousand years ago. so let's, let's look at the model, of what happens there. now the this is t- this is a cartoon but it's, pretty accurate, where you view, here's the edge of the continent here in these little blocks, you can think of this continent initially rifting apart with sea floor spreading, starting to subside as it cools, and here the rivers are starting to flow into it, and of course, they start dropping their sediment pretty fast but it does flow out with turbidites and stuff, and it starts building up this pile like this. and this pile, looks like what we see now. here's here's the shelf here's the s- shelf edge there's the slope, and it just builds up and out, as the, edge of the continent gradually cools and subsides. you with me...? up here, here's the beach somewhere it's stirring up the sediment and moving it off a little bit, down the slope. and then we drop sea level, with an ice age... now this is what i was talking about, suddenly the rivers, that were, originally dumping their stuff up here somewhere, are winding their way across this old shelf, and dumping, their load, right out on this steeper slope. and so what happens, is it starts to build out, another bit of shelf here. the part in the dark shading... sea level rises again this floods back, and you get another, area of buildup slowly out to the edge. so if you had repeated sea level, rises and falls which we have over the last few million years, then you'd see this whole thing repeated again and again and again. and you can see a whole, series of, big progradations big, building out, then small packages and then big ones over the top and then another small one and so on, all the way out until, off the east coast of the U-S where this has been going on for, a hundred and forty million years as we calculated, in our exam, the width here, today, is, a hundred miles or so... huge, broad shelf. <P :10> now... you might think, if you've ever had uh, had to try and uh, decant stuff, that is, let very fine grained sediment and muddy water settle out, like if you go camping and the lake water's a little muddy and you'd sorta like to, drink it but you'd prefer it to be uh, something you could see through before you'd put it, down your gullet... then you might sit around, if you didn't have a filter mechanism with you which would be the best way to do it to filter it out you might just let it settle out. to do that, in most lake waters you'd wait quite a while. you could build up a thirst. it takes a long time to settle it out. and the reason i bring that up is you might think that the very fine grained stuff, even though i've told you it can't go more than a thousand kilometers, you might suspect it could really go further than that, if it ke- kept stirred up in all the waves all the time. but lemme show you what really happens... that's the settling rate, of measured, scientifically measured... of a clay particle... in water. ten-point-five times ten-to-the-minus-four centimeters, every second. now the average depth of the ocean, to the nearest, thousand meters is four thousand meters, or four times ten-to-the-tenth ce- centimeters, and so if we calculate how long it would take, for a clay particle, to settle by normal settling techniques, or normal settling processes, you can figure out, that, that settling rate, divided into four thousand, meters or four times ten-to-the-fifth centimeters, ends up with a, three hundred eighty million seconds, or, equivalent to twelve almost twelve and a half years. to settle out. now most ocean currents, near the edges of continents, we'll talk about later but, let's just say they, a good fast one will be r- moving at, something under a knot but say, say half a knot. that means half a mile an hour. half a nautical mile an hour. you can go a long way at that speed in twelve years. and in fact, you could go across the ocean, no trouble at all, in twelve years. so you would expect, from just this simple calculation, that, a clay particle dumped into the Chesapeake Bay, carried out into the ocean could make it to Spain without any trouble at all. and that when you look at the clay min- uh clays all over the world's ocean, they, they'd be very f- broadly distributed. when in fact they're not. so what's going on? <P :07> it took twelve years for it to sink to the bottom. well it just doesn't happen that way. it doesn't go out there and just float around, and gradually sink down, get stirred up occasionally, gets down to the bottom and gets deposited. what happens is... biology that's what happens... what an uninteresting world this would be if we didn't have biology. biology, sticks its, active nose in almost, every f- part of this world. and this is no different. have what we call filter feeders. you know what a filter feeder is? i bet you can imagine. take a guess. what do you think, Rebecca...? 
SU-F: (xx) sediments (something like that) bottom feeders (xx) 
S1: the- they're nonselective, eaters. it's like my son. anything that comes by 'em, <SOUND EFFECT> they eat it. now there're all sorts of filter feeders. Rebecca, Becca talked about the bottom, filter feeders, which just go in, and just eat mud. anything that's in the mud, that they can digest they digest it, and they excrete the rest. 
S9: are these, like when i was reading today it was saying like something to that extent but wouldn't it also be kinda like, they get a lot of these particles, like that they ate other things or something? like it wouldn't be it wouldn't necessarily be a filter feeder but what if another fish ate another fish, (and then the particle's gone?) 
S1: oh yeah you can you can you can, send it up the food chain, for sure. but down, right above the plants, which is which are, the base of the food chain and the surface ocean, there are a lot of small planktonic or- organisms, who do nothing but, rake through the ocean with these, arms with little hairs on 'em, and grab anything that's there. anything at all. and it's just like the bottom feeders that Rebecca, mentioned, they ingest it, anything they can digest they do anything they can't cannot they excrete. and in fact... i mean uh if it's, if it's really rich, and everything is uh plentiful, they often don't even digest it all. they just eat it and excrete it. pull out a little bit of it. now. what happens then, this clay gets out there and it gets, it gets treated just like it was a diatom, or some other plant, and it's filtered out of the ocean literally filtered out, just like the zebra mussels in the Great Lakes, are filtering the clays out of that we're seeing the bottom of the Great Lakes now, where we've never seen it before. because these are very_ the zebra mussels are very efficient, bottom living filter feeders filtering the water, not the mud, but it's very effective. and what happens? well, filter it out, put it in little turds, and you excrete it as bigger particles and the big particles sink fast... that's why you don't see this clay dispersed all over the world's ocean. the way they prove this, i told you earlier that, that uh war and, and uh, military establishment, often has, side effects that are informative. they discovered this because they started picking up, after the bomb tests of the, fifties and early sixties, they could, pick up, dust particles from these, explosions, that had reached, four thousand meters down to the bottom of the middle of the ocean, within weeks, of the explosion... it was a clear, demonstration, that this dust even though it was very fine, did not settle as individual particles, but settled as little, baggies. of particles. including dust, the remains of organisms that were filtered out, in the upper ocean, and excreted to the bottom. and that way, what we do is preserve patterns in the oceans, that exist, on the sea floor. things that come into the ocean and live in the ocean, and they die, they're usually eaten, or eaten before they die, excreted, and where they live is where you find them on the bottom. where the dust is transported and falls o- into the ocean, go down there's where you'll find it. that's why those patterns of quartz, are clear. they're sharp. they fell into the surface of the ocean, they were filtered out by organisms, excreted to the sea floor. good place to stop. i'll see you folks uh, on, next Tuesday have a nice weekend. 
S4: can i ask a just quick question about that? [S1: sure. ] it would seem like, like so you're saying it would take, a shorter amount of time for stuff to settle? but wouldn't it have to reach the bottom first before the bottom eaters 
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