Seafloor Spreading
Summary
TLDREl video explica el concepto de la expansión del fondo marino, clave en la tectónica de placas. Comienza con la idea de la deriva continental de Alfred Wegner y presenta las pruebas que surgieron después de su muerte. A través de investigaciones y tecnologías como el sonar, los científicos descubrieron la geología activa del fondo oceánico, apoyando la teoría de Wegner. Las pruebas incluyen fracturas en la litosfera, la edad creciente de las rocas oceánicas, el grosor de los sedimentos y los patrones de magnetismo en el fondo marino, confirmando la expansión del fondo y la tectónica de placas.
Takeaways
- 🌍 Alfred Wegener propuso la idea de la deriva continental, sugiriendo que los continentes se mueven lentamente sobre la superficie terrestre.
- 📊 Tras la muerte de Wegener, la evidencia de la expansión del fondo marino surgió, lo que ayudó a respaldar su teoría de la deriva continental.
- 🌊 En la década de 1950, Marie Tharp y Bruce Heezen crearon el primer mapa batimétrico del océano Atlántico utilizando tecnología de sonar.
- 🏔️ El mapa reveló una cordillera montañosa masiva que atraviesa el Atlántico, lo que sugirió una conexión con la teoría de Wegener.
- 🌋 Se descubrió que el magma del interior de la Tierra emerge en las dorsales oceánicas, separando las placas tectónicas en lo que se conoce como una zona de expansión o límite divergente.
- 📅 La edad del fondo marino aumenta a medida que te alejas de la dorsal oceánica, lo que respalda la teoría de la expansión del fondo marino.
- 🪨 La capa de sedimentos en el fondo del océano se vuelve más gruesa cuanto más lejos esté de la dorsal oceánica, lo que también apoya la expansión del fondo marino.
- 🧲 La magnetización del fondo marino mostró patrones alternos en ambos lados de las dorsales, lo que confirmó la inversión de los polos magnéticos a lo largo del tiempo.
- 🔄 Las inversiones magnéticas quedan registradas en las rocas del fondo oceánico, proporcionando evidencia adicional de la expansión del fondo marino.
- 🌐 La combinación de fracturas activas, edades de rocas, capas de sedimentos y patrones magnéticos confirma que el fondo marino se está extendiendo y que la tectónica de placas es un fenómeno real.
Q & A
¿Qué es la expansión del fondo marino y por qué es importante en la teoría de la tectónica de placas?
-La expansión del fondo marino es el proceso mediante el cual el magma emerge desde las grietas en el fondo del océano y empuja las placas tectónicas en direcciones opuestas. Es fundamental para la teoría de la tectónica de placas, ya que demuestra cómo las placas se mueven y forman nuevas áreas de corteza terrestre.
¿Quién fue Alfred Wegener y cuál fue su contribución a la geología?
-Alfred Wegener fue un meteorólogo alemán que propuso la teoría de la deriva continental. Sostenía que los continentes no son masas fijas, sino que se mueven lentamente sobre la superficie terrestre, interactuando entre sí.
¿Cuál fue la primera evidencia significativa que respaldó la teoría de Wegener después de su muerte?
-La primera evidencia significativa fue el mapa batimétrico del fondo del océano desarrollado por Marie Tharp y Bruce Heezen en la década de 1950, que mostró que el fondo marino no era una superficie plana, sino una región activa con montañas, grietas y volcanes.
¿Qué descubrieron Tharp y Heezen al mapear el fondo del Atlántico?
-Descubrieron una cadena montañosa en el centro del Atlántico que imitaba la forma de los continentes, lo que sugería una posible relación con la teoría de Wegener sobre la deriva continental.
¿Qué rol desempeñó el sonar en la investigación del fondo oceánico?
-El sonar permitió a los científicos mapear con precisión la profundidad del fondo oceánico sobre grandes áreas, proporcionando datos cruciales sobre las características geológicas submarinas, como la presencia de dorsales oceánicas y grietas.
¿Qué revela la edad de las rocas en el fondo marino sobre la expansión del fondo oceánico?
-La edad de las rocas revela que las más jóvenes están cerca de las dorsales oceánicas, mientras que las más antiguas se encuentran más alejadas. Esto respalda la idea de que el fondo marino se está expandiendo a medida que el magma empuja las placas.
¿Cómo contribuye el espesor de los sedimentos a la teoría de la expansión del fondo marino?
-El espesor de los sedimentos aumenta a medida que uno se aleja de la dorsal oceánica, lo que indica que las rocas más antiguas han tenido más tiempo para acumular sedimentos, lo que confirma la expansión del fondo marino.
¿Qué son las inversiones magnéticas y cómo se registran en el fondo oceánico?
-Las inversiones magnéticas ocurren cuando los polos magnéticos de la Tierra se invierten. En el fondo oceánico, estas inversiones quedan registradas en el magma que se solidifica y se alinea con el campo magnético de la Tierra en el momento de su formación, creando bandas magnéticas simétricas a ambos lados de las dorsales oceánicas.
¿Cómo se relacionan los patrones de magnetismo en el fondo oceánico con la expansión del fondo marino?
-Los patrones de magnetismo en el fondo oceánico muestran bandas simétricas de polaridad magnética alterna a ambos lados de las dorsales oceánicas. Esto indica que el fondo oceánico se está expandiendo y creando nuevas áreas de corteza a medida que el magma emerge y se solidifica.
¿Cuáles son las cuatro principales evidencias que respaldan la teoría de la expansión del fondo oceánico?
-Las cuatro principales evidencias son: 1) fracturas activas en la litosfera que imitan la forma de los continentes, 2) el aumento de la edad de las rocas a medida que se alejan de las dorsales oceánicas, 3) el aumento del grosor de los sedimentos lejos de las dorsales, y 4) los patrones simétricos de magnetismo en el fondo oceánico.
Outlines
🌍 La teoría de la deriva continental y el descubrimiento del fondo oceánico
Este párrafo introduce la teoría de la deriva continental propuesta por Alfred Wegener en los primeros años de 1900. Wegener sugirió que los continentes no eran masas estacionarias, sino que se movían lentamente a lo largo del tiempo. Aunque en su momento no había evidencia suficiente para probar esta teoría, el descubrimiento del fondo oceánico proporcionó nuevas pruebas para explicar el movimiento de las placas tectónicas. A través de métodos como la cartografía batimétrica realizada por Marie Tharp y Bruce Heezen en los años 50, se descubrió que el fondo oceánico no era plano, sino una región activa con montañas, volcanes y fallas, lo cual apoyaba la teoría de la deriva continental.
🌊 Edad del suelo oceánico y la expansión del fondo marino
El párrafo describe cómo la edad del suelo oceánico proporciona evidencia para la expansión del fondo marino. Las rocas más jóvenes se encuentran cerca de las dorsales oceánicas, y a medida que uno se aleja de estas, las rocas se vuelven más antiguas. Este patrón confirma que el magma emergente en las dorsales empuja las placas tectónicas a ambos lados, lo que apoya la teoría de la expansión del fondo marino formulada por Harry Hess y otros científicos.
🧱 Sedimentación y prueba adicional de la expansión oceánica
En este párrafo se explora la sedimentación como otra forma de evidencia de la expansión del fondo oceánico. Las capas de sedimento en el fondo del océano se vuelven más gruesas a medida que uno se aleja de las dorsales, ya que las rocas más antiguas han tenido más tiempo para acumular sedimento. Este hallazgo, corroborado por estudios cartográficos de la sedimentación, refuerza la idea de que el fondo oceánico se expande y que las placas tectónicas se separan en los centros de expansión.
🧲 Reversiones magnéticas y su registro en el suelo oceánico
Este párrafo explica cómo los patrones de magnetismo en el suelo oceánico proporcionan una prueba sólida de la expansión del fondo marino. A lo largo de la historia geológica, los polos magnéticos de la Tierra han cambiado, y estos cambios se registran en el magma que emerge y se solidifica en las dorsales oceánicas. Estos patrones de magnetismo, que coinciden a ambos lados de las dorsales, son evidencia directa de que el suelo oceánico se está expandiendo y que las placas tectónicas se separan.
🧭 Reversión de los polos magnéticos y la evidencia final de la expansión oceánica
El párrafo final resalta cómo las reversiones de los polos magnéticos y su registro en el fondo oceánico proporcionan una cuarta pieza de evidencia para la expansión del fondo marino. A través del registro magnético de las rocas, se puede observar que las bandas de magnetismo a ambos lados de las dorsales oceánicas son simétricas, lo que confirma que el suelo oceánico se expande. Esto completa el conjunto de pruebas que demuestran la veracidad de la deriva continental y la tectónica de placas.
Mindmap
Keywords
💡Expansión del fondo oceánico
💡Tectónica de placas
💡Alfred Wegener
💡Dorsal mesoatlántica
💡Mapas batimétricos
💡Magnetismo del fondo oceánico
💡Inversión magnética
💡Edad del fondo oceánico
💡Sedimentos
💡Fallas y escarpes
Highlights
Introduction to seafloor spreading, a key concept in plate tectonics.
Alfred Wegener's proposal of continental drift, suggesting continents are moving slabs of rock.
Early mapping of the ocean floor through methods like line sounding, providing crude and unreliable data.
Post-World War II advances in mapping the ocean floor using sonar, led by scientists like Marie Tharp and Bruce Heezen.
Discovery of the mid-ocean ridge, a massive undersea mountain range that mimics the shape of continental coastlines.
Harry Hess's theory of magma pushing up from beneath the Earth's surface, creating spreading centers along mid-ocean ridges.
Age of seafloor rock increases as you move away from mid-ocean ridges, supporting the concept of seafloor spreading.
Sediment layers on the ocean floor thicken as you move away from mid-ocean ridges, another piece of evidence for seafloor spreading.
Use of magnetism during World War II to detect German submarines led to the discovery of alternating magnetic stripes on the ocean floor.
Earth's magnetic field periodically reverses, and these reversals are recorded in the solidified rock at mid-ocean ridges.
Magnetic stripes on either side of mid-ocean ridges match, providing further evidence of seafloor spreading.
Earth's outer core generates the magnetic field due to the movement of molten metals like iron and nickel.
Four key pieces of evidence support seafloor spreading: fractures in the lithosphere, age of rock, sediment thickness, and magnetic patterns.
Seafloor spreading and plate tectonics are now widely accepted phenomena due to the accumulated scientific evidence.
Conclusion emphasizing that seafloor spreading proves the theory of continental drift and plate tectonics.
Transcripts
in this video we're going to discuss
seafloor spreading a key geological idea
and one of the foundational concepts
behind
plate tectonics to begin we're going to
go way back to the early 1900s
and a german meteorologist named alfred
wegner
who was proposing a radical new idea
that he called
continental drift this idea proposed
that the continents were not
stationary masses but rather slowly
moving slabs of rock that interacted
with one another
over time but in order to really make
sense of this idea
we need evidence now fortunately
after wegner's death evidence became
available in a variety of forms
and that evidence also describes the
process that we now know
as seafloor spreading so in this video
we're going to look at these four key
pieces of evidence
to support and describe this idea
the first thing we're going to look at
is the ocean floor now
in the days of wegner we were limited in
the amount of data and information we
had about the sea floor
for hundreds of years we had been able
to collect some crude information
by doing methods such as line sounding
where you would drop
a rope with a weight on the end down to
measure how deep different parts of the
ocean were
and if you did this in enough areas you
can create a
simple and basic map of the ocean floor
unfortunately these maps were as i
mentioned very crude and very limited
and
unreliable but as world war 1
began and ended and then eventually
world war ii came about
the united states launched a department
of the navy
office of naval research and for the
first time
science was driving an effort to map the
ocean floor
in fact scientists marie tharp and bruce
heezen developed the first
bathymetric map of the atlantic ocean
and this is in the 1950s
they used a technology known as sonar to
map
accurately the depth of the sea over
large
areas and they created a map that
was the most accurate of its time and so
if we were to
look at the world today and actually
take the blue oceans
and drain them from the surface what we
would see
is that the sea floor is not a vast
expanse of
flat desert as was believed beforehand
but rather it was a jagged and active
area
with giant peaks and cracks
trenches earthquakes and active
volcanoes
as you can see here now that we've
drained out the water from the earth
if we zoom in on different areas
particularly the
center of the north atlantic ocean and
extending down through the southern
atlantic
you see this massive scar this
thousands of mile long mountain range
that runs down the atlantic ocean basin
and essentially mimics the shape of the
continents
this set off some alarm bells for
scientists
as they believed that this could
potentially be related to wegner's
earlier theory
of the moving continents
after the work of tharp and hezen came
along other notable scientists including
robert dietz and harry hess
who published work that further
described
the fascinating geological structures
that are found in the bottom of the
ocean
in fact if you were to draw a profile
from north america to europe
you would see something like this with
vast expanses of flat areas
and then that jagged irregular central
mountain range that runs down the center
of the atlantic ocean
and so this simple observation that the
seafloor has
geology became supporting evidence
number one
so there are active fractures
in the lithosphere or the crust of the
ocean floor
in a pattern that appears to mimic the
shape of the continental coastlines
based on these observations scientists
like hess
developed an idea that along this ridge
magma from underground magma chambers
was spewing up through the crack in the
earth's surface
and pushing the plates apart pushing the
slabs of rock on either side
away from one another in what would
become known
as a spreading center or a divergent
plate boundary
as seen in this animation here slowly
over time the plates
spread apart carrying the rock and the
sediment with them
and along this boundary we see lots of
cracks called
faults and scarps in the surface of the
earth
here's another diagram that illustrates
what we think happens
along these spreading centers where
magma pushes its way
up through the crack and spreads the
plates apart above
and so one of the ideas was to look at
how
old the rock on the seafloor is as that
could potentially support this notion
and if you were to map the age of the
seafloor
similar to what we see here what you
would notice
is that shown in red we have very young
rock right along the ridge and then as
you go away from the ridge in either
direction through the orange and yellow
to the green and then blue the age of
the sea floor gets
older and so the only way that's really
possible
is if in fact sea floor spreading is
occurring
and that harry hess and other scientists
were correct
in their theories so supporting evidence
number two
is that the age of the seafloor rock
increases
as you get further away from the mid
ocean ridge
but as with all science we're constantly
looking for more supporting evidence
and so scientists went back to the
drawing board and they thought about
other things that could prove
that this is in fact happening
so something else they decided to look
at was sediment
now sediment refers to sand and clay and
other bits of rock and organic matter
that settles on the bottom of the ocean
similar to the idea that young rock
should be found near the mid-ocean ridge
and old rocks should be found further
away scientists believe that
sediments should become thicker in their
layers
as you get further from the ridges which
makes sense because
older rock would have had more time to
accumulate sediment
as you can see in this diagram if you
were to travel along the sea floor from
point a
to b to c to d you would notice that
that layer of sediment
increases in its thickness and that's
because the rock is older and there's
been more time for the accumulation of
that sediment
and this proved to be true as we studied
the seafloor more and more
as with this map showing sediment
thickness with different colors
with the dark blue being thin layers of
sediment
and light blue to green to yellow and
red becoming thicker
and thicker and so that gives us
supporting evidence number three the
thickness
of the layer of sediments deposited on
the ocean floor
increases as you get further away
from a mid-ocean ridge and so once again
we would look to
warfare and the navy to get more
scientific information to support the
concept
now during world war ii one of the
issues that the americans and our allies
were dealing with
was being able to identify these massive
sea
mines and submarines that were being
used by the germans
and so one thing we did was begin to
study
magnetism using new technology
we could travel across the ocean in a
boat or in an airplane
and detect the magnetic field under the
ocean's surface
now submarines and mines give off a
certain amount of magnetism
or are sensed by this equipment and so
we are able to actually
detect them even if they're out of
visible site
but we also were able to detect
magnetism
of the sea floor and we found something
fascinating
which is that if you look at the
magnetism of the sea
floor in different areas it's not
random as you might expect but rather
you see these
bands or stripes of alternating
magnetism
as seen in this diagram or this one here
now in order to really understand this
we need to step back a little bit
and actually look at the inside of the
earth
in case you were unaware the inside of
the earth is made up of different
layers and one of those layers the outer
core shown here in orange
is composed of molten metals including
iron and nickel now those molten liquid
metals
are not sitting still but rather they
are flowing around the inner core
and the movement of that liquid metal
generates a magnetic
field which essentially turns the earth
into one gigantic
magnet now the fact that the earth is a
magnet and has a magnetic field is very
important for a lot of different reasons
which we won't get into in this video
but it's important that you know the
earth essentially is a magnet
and just like a magnet that you would
play with it has both a north and a
south
pole that behave a little bit
differently and are detectable
now a strange phenomenon we have seen on
earth is that
the magnetic north and south poles
switch
periodically over time so if you look at
this visualization
let's say that the orange area
represents the magnetic north and the
blue represents the magnetic south
now over time those poles will become
kind of all haywire
and then eventually flip so that north
has become south and south has become
north this is known as a magnetic
reversal
and we see it happen on a fairly regular
time scale
throughout earth's geologic history
now here's why this is so important and
relevant to seafloor spreading
it's because these magnetic reversals
are captured in the solidified rock on
either side of a mid-ocean ridge
as magma wells up through the ridge
and hits that cold ocean water and
solidifies
into rock minerals within the magma
align with the earth's magnetic field
and then we forever have a record of
what the earth's magnetic field
was at the moment that that rock formed
let's look at this animation which shows
it clearly
that as magma upwells and solidifies
it records the earth's magnetic field
and whenever those switches occur
we see it as a record within the rock
now it's shown here with different
colors black and white
within the rock which of course is not
the case in reality
however if we could see the seafloor
magnetism we would see patterns that
look kind of like this
if we were to come back over this area
with a boat
and measure it what we would see is that
the pattern of magnetism matches up
perfectly
on either side of the ridge where we see
positive magnetism on the left side it
aligns with a similar band on the
opposite side
and the only possible way that this
pattern could exist
is if the seafloor is spreading and so
this becomes supporting evidence number
four patterns of seafloor magnetism on
either side of a mid-ocean ridge
matches up with one another and so
this gives us a complete case that
proves that the sea floor
on earth is in fact spreading apart and
that plate tectonics is a real
phenomenon
so when we look at the earth and we see
these fascinating structures under the
ocean
we now understand why all we have to do
is look at these four key pieces of
evidence
just to review them quickly here they
are
number one there are active fractures in
the lithosphere along the ocean floor in
a pattern
that mimics the shapes of the
continental coastlines
number two the age of the rock of the
sea floor
increases as you get further away from
the mid-ocean ridge
number three the thickness of the layer
of sediments deposited on the ocean
floor
increases as you get further away from
the mid-ocean ridge
and finally number four patterns of
seafloor magnetism
on either side of the ridge match up
with one another
and so now we accept the fact that the
oceans are in flat
spreading apart and that continental
drift and plate tectonics
are true phenomenon that we see on earth
thanks for watching
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