Welcome back for another lecture this
one on earth's oceans it's kind of a
long one. We'll kind of zip through it
a little bit but it does cover quite a bit
of content so this is really kind of
like your full-on crash course into
Oceanography the other videos I posted I
introduced really the fundamentals of
coastlines some of the features looking
at the difference of waves and tides and
currents so this one's going to be a
little more about how do we understand
the oceans how do we see the oceans and
what are the different attributes and
levels so let's just jump in so the vast
world ocean so there's really just one
ocean right so we've got our identified
as the blue planet about 71% about
three-quarters or so of our planet is
covered by oceans by one ocean or four
ocean basins oceanography utilizes
geology chemistry physics biology all
that to study the oceans a lot of people
take oceanography as a course in Iran
what I'm going to talk about all the the
dolphins and the whales and it's like
that's more of a marine biology course
oceanography has really been
understanding the fishbowl and all of
its contents and how it works and the
chemical composition so it's a little
more complex than just the animals that
get to play around in it so we have four
ocean basins we've got the Pacific the
Atlantic at the Indian and the Arctic
beyond that we do have other regions
that we identifying a seas and stuff
like that but these are the big four
so the Pacific is the largest as the
greatest depths it covers about 30% of
our planet the Atlantic is about half
the size of that and only covers about
20% the Indian Ocean is a largely
southern hemisphere body and
significantly smaller than the Atlantic
and then the Arctic is the smallest it's
only about one and a half times the size
of the United States so it's actually
the smallest ocean that we have but
again we have these four ocean basins so
how do we map it well you know we know
way more about space than we do our
oceans which I think says a lot with
just how we look at TV right there's so
many different television shows that
deal with space and the frontier
we don't only have a lot of seat well
okay we've got one of the sharks is stop
sharknado but those aren't real
scientific videos and television shows
but looking at mapping the ocean floor
so we use bathymetry which is a
measurement of ocean depths and
topography we use sonar satellites
submersibles they allow us to study the
ocean floor more efficiently we really
didn't know a lot about what was
underneath the oceans until World War
two when we started using sonar and
looking at the ocean floor by looking at
the ocean floor then it allowed us to
understand that we have divergent zones
we've got these rifts and that when
that's when the whole the information
that was needed to prove the theory of
plate tectonics was then developed
because then we had you know that last
nail in the coffin we can now prove
beyond a reasonable doubt this is how
the bigger picture works so we look at
all these different things so what I did
is I just chose a photo of you a map
itself of the of the world and showing
all the different continents and then
the ocean floor so let's talk about some
of the ways that we map it and produce
this bathymetry which is these beautiful
maps that show what the ocean floor
looks like and a great example of this
would be looking at Google Earth and
flying over the oceans and seeing all
the depth the the you know looking at
the volcanic arcs and looking at all the
different attributes so the first one is
looking at sonar which I don't know if
you I didn't know there's the sonar is
an acronym for sound navigation and
ranging so it's a transmission of sound
waves towards the ocean floors the way
that is essentially done is they send
down a sound and then the sound bounces
off the floor and comes back up like an
echo right and but based on how long it
takes that echo to come back gives us a
calculation of the depth of the ocean
floor so then we're able to then you
know read that so this is the way it was
done we still do this a little bit now
we do a lot more of the digital scanning
that's able to get us down there looking
at satellite imagery so it measures
small differences using microwaves so
this provided that not all worship
floors are flat themselves so looking at
satellite imagery not just photography
but looking at again the different waves
that are sent back and forth looking at
color imagery and looking at depth that
way so there's lots of different
attributes that we can look at but these
are all different ways that we can
visualize the ocean floor so here we
have a satellite in orbit outgoing radar
pulses and then they bounce back here we
have the elevation to see the surface
height ocean floor and return the pulses
from the sea surface so I think it's
this kind of you've probably you've seen
this before at some point but let's talk
about the margins this is really
important for us because you know we are
surrounded by margins around our
continents so the Continental margin is
a zone between the continents and the
ocean base and being really looking at
the continental crust moving into the
oceanic crust and the margin itself is
that transition zone if you notice on
width on top of this we have a shelf
this shelf is material that's been
deposited out into that transition zone
so in the Atlantic thick layers of
sediment cover cottageville margins low
volcanic and limited earthquake activity
so we have all of this going on in the
Atlantic the Pacific we have a very
short continental shelf because we have
a margin looking more at the Atlantic
they have a much longer shelf what's
interesting also about the margin itself
looking at places such as Florida we can
see that this is where because it's very
shallow where a lot of their coral reefs
were developed because coral develops
well in shallow warm water so it usually
develops here on a margin itself on the
shelf looking here at this deep sea fan
this that's interesting this is really
essentially you have a submarine canyon
and all that material the submarine
canyon is where all of the sand that's
along the beach line will drain out into
and then create this this fan shape down
here into the the rise and then the
abyssal plain the abyss is out in the
middle no or just super super super far
out there so now we have these margins
if you remember from one of our
activities we cut out the the different
continents and we took them as as they
look today including the shelf and then
we had to merge them back together to
replicate Gondwana
you know looking at one of our tectonic
spooning events and in doing that you
you had to use the shelf as part of that
seam to put these back together so maybe
that new brings back some memories so
some of the ocean floor features we've
got there the continental shelf
submarine canyons and then turbidity
currents so I'll take a moment to
introduce each one of those so again the
continental shelf is a gently sloped
submerged surface that extends from the
shore line outward into the ocean it can
contain important mineral deposits oil
natural gas and gravel that being said
within the continental shelf that's
where they do a lot of offshore drilling
in Florida in particular that's where
they get a lot of their natural gas
reserves for us and on the Pacific in
California that's where we get a lot of
our oil reserves
these submarine canyons are seaward
extensions of a canyon that's been
carved into the outer continental shelf
in which the longshore current brings
material along the beach hits a
submarine canyon and takes that material
out into the ocean and beyond and then a
turbidity current is a downslope
movement of sediment Laden water so it
means that's you've got it's like mud
and that's caused when the sand and mud
of the continental shelf or dislodged
and become suspended so imagine really a
turbidity current is like a landslide of
material that then breaks off of the
shelf goes out into you know beyond into
the abyss but all of that
turbidity just means it is muddy and
murky because all that material has been
resuspended and will then have to be
laid out and deposited so looking at
some of these things I guess I found
this diagram I thought it was quite
helpful so here we have our submarine
canyons here we have this material that
builds up and here they give an example
of a turbidity current what's
interesting about these they can also be
graded bedding so looking at what we
consider sedimentology which is in the
geology family is that then they would
look at these different layers and see
these are different events we find that
generally the coarser grain material
will develop well sorry well deposit
first because it's heaviest and then you
kind of work through your different
layers
of grain size so you need a lot of
energy live material to move bigger
grain stuff then you have you know
medium very you know then maybe very
fine
you know coarse medium fine coarse
medium fine so in this particular image
they're giving us we have for visual
turbidity currents that have deposited
on these fans this also can give us some
information about some of the local
geology looking at the different
material that had been deposited within
the shelf over time so again this is
this doesn't have to just be sand I can
you know maybe there's been you know
volcanic events you know on the land or
maybe nearby that it put an ash may be
looking at different broken bits of
coral reef so it's different ways that
we can look at the local hist reality so
here's three more we have content rise
the abyssal Plains and sea mounts the
content will rise as a gently sloping
surface at the base of the slope because
it's rising up the abyssal plain is a
very large area of deep ocean floor
that's why I keep referencing it's the
abyss it's way out there and this is
very very vast and then sea mounts
they're isolated volcanic Peaks that
rise at least a thousand meters above
the ocean floor so meaning that these
sea males are essentially volcanic
mountains that these volcanic mountain
ranges that exist very very deep beneath
the ocean so like we like to think in
California you know that we have Mount
Whitney which is like our Everest at
over fourteen thousand five hundred
eight feet from zero upward but if we
were to then look at the landscape and
remove all the ocean water and look at
some of the mountain ranges that exist
on the oceanic crust and their height
that's actually some the tallest
mountains and some of the deepest holes
in the world are found out in the oceans
because you have to take from their
surface to their peak which is pretty
impressive so here's a diagram this is
windy this is using a scan so what
they've been able to do here is we can
see down below this is your oceanic
crust this is your volcanic peak these
are all different deposits this is
sedimentary geology right here it's best
different layers and material so what
this scan was able to do
it was able to then obtain and read this
harder igneous rock and then all and be
able to distinguish the densities and
thicknesses of all these other
sedimentary layers that lie on top this
is important because it gives us a
better image to understand what's
underneath because if you were just
scanning the top you see this one
volcanic peak and not understand there's
so much more oceanic crust that's not
been observed because it's been covered
by all of this material so what about
some of those sediments so here we
mentioned there's different sediments
here but what are those well here's some
different types of sediments you have
bio genius sediments which consists of
skeletal remains remains of marine
animals and algae you have calcareous
which is like a thick news from the
dissolving calcium of carbonate shells
you have salacious ooze which is silica
based it's a news composed of silica
based single-celled organisms and algae
and then you have a hydrogenous sediment
which is the mineral crystallization
from the ocean waters through chemical
reactions so these are four very common
sediments that we observe on oceanic
floors bio genius calcareous salacious
and then hydro genius the one that I
think is the most interesting is the
calcareous ooze yes because it's kind of
fun to say but even though giving the
bio genius sediments the consist of
skeletal marines of marine animals algae
perhaps you've seen chalk got a
chalkboard that's usually bio genius
sediments looking at chalk because it's
broken up skeletal Marines in ocean so
looking at the White Cliffs of Dover as
part of that material breaktime
okay that's a couple more slides so that
was really crash course in understanding
the Earth's oceans how we very quickly
look at it again this is the compliment
a lot of the material that you have in
the course so let's look more at the
seawater
so we've now very briefly looked at what
we see on the ocean floor but what about
the oceanic water well let's first speak
about salinity
or salt so we know that salt exists on
our planet it's a natural mineral it
comes from rock we know that if you've
ever boiled water and you forgot about
it and you come back and there's just
white powder and the bottom of the pan
that is because the water can evaporate
and it can go away but it cannot take
the minerals behind and those minerals
that are left behind are called
evaporates right because you've
evaporated all the water leaving those
minerals behind so what can change
salinity in the ocean so if you want to
decrease the salt and the water in the
ocean
you either have advanced or progressed
precipitation you have sea ice and
icebergs melt or you have more runoff so
essentially to decrease the salinity of
the ocean what do you need to do you
need to add water to the ocean there was
a saying a long time ago it's not true
but it said it was the solution to
pollution is dilution right that's not
true but they used to think that because
if you complete you know if you continue
to dilute that it's slowly it'll become
so small that you tarly even notice that
it's there but it never really goes away
so it'd be kind of like getting I don't
know like a glass of water and putting a
little bit of salt in it and then trying
to add more and more water to it to try
and flesh out the salt but you can never
really get rid of the salt it's just you
add more water to it which makes it a
lot weaker well how do you increase
salinity well by advanced evaporation or
by glaciations so by maybe the ocean
waters getting a lot warmer by more
radiation being absorbed by the oceans
and planet creating warmer air can
increase evaporation rates so taking
water out leaving the salt behind and
become saltier glaciation so again water
is being pulled out of the oceans and
being stored in the landscape leaving
more salt behind right so imagine maybe
you are making a Top Ramen you know the
square in salt powder and you put it on
there but you forget about you boil it
after you've added the salt and most of
the water has gone away you'll notice
that it's almost like a syrup it's so
dick you know right because that salt
you have to add more water to it well
that's what happens here
by evaporating that excess water it
becomes a lot more intense looking at
salinity so there are measurable
proportions of dissolved material in
water and that can be expressed as parts
per thousands so what we can do is we
look at water and try to see what's in
it
so obviously within the ocean we have
water and salt are there other things
yes there's lots of other things there's
nitrogen and carbon all kinds of other
elements that have been absorbed within
it but think about just like your
drinking water right in your bottled
water that you buy at the store think of
all the things that have been added to
it you can't see it but it's there and
you know it's there because if you're
like me you know there's a definite
difference in taste between Dasani and
Aquafina I can't stand either those but
if I had to drink 100 Aquafina I don't
know why I think the song is terrible
but there are then measurable
proportions of dissolved material in
that water that gives it the flavor that
you want right think about it something
different food Coke and Pepsi
some people like Coke some people like
Pepsi and there's people who do not like
them and do not like Pepsi it's because
there's something in that solution that
either you like or you dislike we can't
see we just can't like pick it out of
there right most of the sodium chloride
whooshes table salt sources include
rocks and chemical weathering of the
rocks and mineral that's where it comes
from
you should be the saying that when
you're out if you're ever stuck in the
desert and you're dehydrated to just
grab some rocks on stuck on a rock
because there's usually salt on the
rocks themselves it will help you help
make your mouth water so you can try to
retain some of that moisture I'm not
saying you should go suck rocks I'm just
saying it was a thing well because of
this composition of seawater this kind
of reflects on an earlier presentation
we can create density so changes based
of salinity and temperature can create
densities so saltier and colder water
have a greater density and are able to
sink so this is really looking at these
current systems so we have deep current
cold salty water that can mix with
shallow warm water as we have this cycle
which water can travel this is really
important for really the whole bio
system
system in our landscape right because by
having this constantly moving water
you're moving temperature around so
you're taking warm water mixing with
cold water and making cool water you're
also taking all of the material
so usually plankton final plank and
stuff like that then able to be able to
mix some of that around but then you're
also allowing corridors for animals and
other things to kind of take a freeway
system that they can jump into to
migrate so looking into that this is a
diagram showing then looking at
temperature so ocean surface temperature
varies because of solar radiation so
this third my client is oceanic water
between three hundred meters and a
thousand meters in depth where the
dramatic temperature changes with depth
so it creates a barrier essentially a
marine life so what I have a I told to
this diagram on its side so we can look
at then these are latitudes going across
and then we can see temperature and
salinity the temperature is observed in
the red salt is observed in the blue
line so we can see at the equator which
is where it's usually the warmest and
most consistent the water is much warmer
right but because it's warmer we also
find that it's less dense that's weird
why would you think that I'll give you a
minute well what happens in these areas
it rains a lot right so you're gonna
find that there's a flux in that amount
of precipitation exchanging the solidity
look at places where it doesn't rain as
much you know we can look at areas like
this 40 north 40 south we can see that
the water is starting to cool down we
have this another barrier that builds in
here see these barriers that exist so
anyway just another diagram to kind of
put it in perspective so let's talk
about the diversity of life this is as
far as we're gonna go into life again
marine biology is of course you would
take to learn about it but we like as
oceanographers to look at the diversity
some rate organisms are classified
really by their location and their
motion we find that it's very easy to
classify things like that another thing
that we classify a very similar would be
clouds we're looking at atmosphere we
classify clouds based on their altitude
and the way that they look their shape
so we can really do a lot with this
elements so we have the plankton nekton
and bentos so plankton are all organisms
animals and bacteria they just drift
they can't they have no control over
where they're going they're just
floating around they don't have the
ability to really be able to control
their location right nekton are all
animals capable moving independently so
they have fins they can they can control
exactly where they're gonna go
and then bent those are the ones that
live on the floor so these are the your
crabs your sponge and stuff like that
that live on the bottom so you know I
don't know I don't know how if it made
help but looking at plankton connected
and benthos there's often a comparison
with SpongeBob SquarePants you know who
would be what right who would be video
plankton who would be considered and
nekton versus who'd be a benthos so
looking also with diversity of life we
have these zones we have the pelagic
zone the benthic and the abyssal zone
so the pehle jayegi zone is of any depth
where animals are able to move freely
and swim around the benthic or sea
bottom surfaces regardless of distance
to shore and in the abyssal zone is a
subdivision of the benthic benthic
excuse me it's extremely high pressure
very low temperatures and low oxygen and
very limited to no sunlight there's too
many commas there exactly
so think about with in the news all the
time I don't know why always happens to
be somewhere near Russia but it always
seems to be in Russia where they come up
and say look we found these these fish
or this marine life that we've never
ever seen before and it's usually
observed and picked up out of a place
under the abyssal range because it's
really really high pressure very very
dark very very very cold so it requires
a lot of work usually I mean it's very
rare that you'd send a person down to
this type of zone because it's just not
safe because you know they could get the
bends on the way up and also because
it's very hard to control all that
pressure and it's very expensive but
usually sends some form of robotic down
there to capture these things so the
logic the benthic and the abyssal zone
which brings us to this diagram this is
that that classic what I like
get together so how can we see
everything together again so we can see
all these different zones here's the
benthic the abyssal then you can also
see the pelagic zone are there other
things on here absolutely I wasn't going
to try to photoshop everything out of
here but I think that this really helps
put things together here we have our
continental shelf here you have your
high tide mark low tide mark your Beach
your coastline so you can start seeing
how all of this somewhat merges together
with the previous presentation that I've
posted so diversity of life what's
interesting here sunlight the sunlight
is you know backtracking a little bit
the Sun gives off visible light the
visible light itself is not hot it's
very it's a shortwave radiation of
visible light what ends up happening is
that surfaces are able to absorb that
light and then you know transform that
energy into long wave radiation which is
identified as sensible heat which means
you can touch it so as you can see it's
a very small area of the ocean on the
top that's able to absorb that sunlight
right the ocean reflects a lot of it but
it's able to absorb a little bit and in
doing so but they're calling the photo
exone that's gonna be your warmer waters
that's gonna be the areas especially
over here where you're gonna to be able
to develop coral reefs what's
interesting about this is that maybe
you've experienced this very bad example
but like in a pool like someone's a big
backyard pool where the water is really
warm right here in the shallow end and
all of a sudden you go to the deep end
it's freezing well that's essentially
the same idea is that the Sun is only
able to reach and go through a certain
depth of that pool and then everything
else below it just gets really really
cold because cold dense water right
brings us all back to that alright well
I know that was a lot of information and
I know I speak fast but I just wanted to
kind of jump through this to give you an
idea of what really Earth's oceans are
about how we look at it the words that
we use the different types that we do
looking at the different diversity of
life looking at those three families
trying to break things up them to
categories such as that I hope you
enjoyed and we'll talk soon
