SEAFLOOR SPREADING THEORY | HOW TO CALCULATE THE RATE OF SEAFLOOR SPREADING | MAGNETIC REVERSAL
Summary
TLDRIn this educational video, students learn about the seafloor spreading theory, which explains the movement of tectonic plates. Key concepts include the history of continental drift, the discovery of mid-ocean ridges, and the process of new seafloor formation at these ridges. The video guides students through a simulation activity to visualize seafloor spreading and discusses the evidence supporting the theory, such as magnetic stripes and the age of rocks near the ridges. It also covers the calculation of the rate of seafloor spreading, enhancing understanding of this geological process.
Takeaways
- 🌐 The continental drift theory posits that all continents were once part of a single landmass called Pangaea, which broke apart and drifted to their current positions.
- 🔍 Evidence for continental drift includes the fit of continents, fossil records, rock and mountain range similarities, and coal and glacial deposits.
- 🧐 Alfred Wegener's initial theory of continental drift was not widely accepted due to a lack of explanation for the mechanism of continental movement.
- 🌊 The advancement of technology allowed scientists to map the ocean floor, discovering mid-ocean ridges similar to those on land.
- 🔥 Harry Hess proposed seafloor spreading in the 1960s, suggesting that continental movement is driven by this process.
- 🌋 Seafloor spreading occurs at mid-ocean ridges where new oceanic crust forms as magma rises and solidifies.
- 🧲 The magnetic stripes pattern near mid-ocean ridges, with normal and reverse polarities, is evidence of seafloor spreading.
- 📏 The age of rocks near mid-ocean ridges decreases with distance from the ridge, indicating younger rocks closer to the spreading center.
- ⏱️ The rate of seafloor spreading can be calculated using the distance between magnetic stripes and the time since their formation.
- 🌍 The process of seafloor spreading is integral to understanding the movement of tectonic plates and the evolution of the Earth's continents.
Q & A
What is the concept of 'seafloor spreading' as discussed in the script?
-Seafloor spreading is a geological process where new oceanic crust is formed at mid-ocean ridges due to the upwelling of mantle material, which then cools and solidifies. This process causes the seafloor to spread outward as tectonic plates move away from the ridges.
What evidence supports the continental drift theory mentioned in the script?
-The evidence supporting continental drift includes the fitting edges of continents, fossil records of prehistoric organisms, similarities in rock and mountain ranges, and the presence of coal and glacial deposits.
Why was Alfred Wegener's idea on continental drift not accepted by his colleagues initially?
-Alfred Wegener's idea on continental drift was not accepted because he failed to explain the mechanism by which the continents could move and drift apart.
What are mid-ocean ridges and how are they related to seafloor spreading?
-Mid-ocean ridges are underwater mountain ranges found in the middle of the ocean floor. They are related to seafloor spreading as they are the sites where new oceanic crust is formed due to the upwelling of magma from the mantle.
Who proposed the seafloor spreading theory and how does it relate to the movement of continents?
-Harry Hammond Hess proposed the seafloor spreading theory in the early 1960s. It relates to the movement of continents by suggesting that the continents move apart as new crust is formed at the mid-ocean ridges, and old crust is consumed at subduction zones.
What materials and tools are needed for the seafloor spreading simulation activity described in the script?
-The materials and tools needed for the simulation activity include board paper or a paper folder, long size construction paper, a pencil, pen or colored pencil, a pair of scissors, paste or glue or sketch tape, and a ruler.
What do the stripes in the seafloor spreading simulation represent?
-The stripes in the simulation represent the rocks with normal and reverse polarities, which are indicative of the magnetic field's orientation at the time the rocks were formed.
What is the role of the mid-ocean ridges in the movement of lithospheric plates?
-The mid-ocean ridges are the origin of the lithospheric movement. They are where the force that pushes the lithospheric plates originates, as new crust is formed and pushes the plates apart.
How does new seafloor form at the mid-ocean ridges?
-New seafloor forms at the mid-ocean ridges as hot, less dense material from below the Earth's crust rises towards the ridges. This material flows sideways, creating a crack in the crust where magma flows out, cools down, and becomes new seafloor.
What processes occur at the sides of the mid-ocean ridges?
-At the sides of the mid-ocean ridges, the process of seafloor spreading occurs, where new crust is formed. Additionally, the old seafloor is destroyed at subduction zones where one tectonic plate moves under another.
How can the rate of seafloor spreading be calculated using the magnetic field graph?
-The rate of seafloor spreading can be calculated by measuring the distance between magnetic stripes on the graph and dividing it by the time represented by those stripes. The rate is then converted from kilometers per million years to centimeters per year using appropriate conversion factors.
Outlines
🌏 Introduction to Plate Tectonics and Seafloor Spreading
This paragraph introduces the concept of plate tectonics and the theory of seafloor spreading. It begins with a brief overview of Alfred Wegener's continental drift theory, which posits that all continents were once part of a single landmass called Pangaea. Evidence supporting this theory includes the fitting edges of continents, fossil records, and geological similarities across different landmasses. However, Wegener's theory was initially met with skepticism due to a lack of explanation for the mechanism of continental movement. Advances in technology and oceanographic research led to the discovery of mid-ocean ridges, which are underwater mountain ranges that play a crucial role in the process of seafloor spreading. The paragraph sets the stage for a simulation activity designed to illustrate the zipper-like spreading of the ocean floor.
🔍 Exploring the Mechanism of Seafloor Spreading
This section delves into the mechanics of seafloor spreading, which was proposed by Harry Hess in the 1960s. It explains that the mid-ocean ridges are the sites where new seafloor is formed as hot, less dense material from beneath the Earth's crust rises and creates magma that solidifies into new crust. The process at the ridges is contrasted with that at the subduction zones, where old seafloor is destroyed as one tectonic plate is forced under another. The paragraph also discusses the evidence for seafloor spreading, including the pattern of magnetic stripes created by the alignment of magnetic materials in the cooling magma with the Earth's magnetic field. These stripes provide a record of the Earth's magnetic field reversals and support the theory of seafloor spreading. The paragraph concludes with a brief mention of an activity to calculate the rate of seafloor spreading.
⏱ Calculating the Rate of Seafloor Spreading
This paragraph focuses on the activity of calculating the rate of seafloor spreading. It describes a method using a magnetic field graph, a ruler, and a calculator to measure the distance between normal polarity readings on the graph, which correspond to the distance of seafloor spreading over time. The process involves measuring the distance between peaks of normal polarity on either side of the mid-Atlantic ridge and using the time scale provided to calculate the rate of movement in centimeters per year. The example given calculates the rate for peak 1 west, converting the distance and time into the appropriate units to find the rate of seafloor spreading at that location. The paragraph emphasizes the importance of understanding the rate of this geological process.
📚 Summary of Seafloor Spreading Concepts
The final paragraph summarizes the key concepts discussed in the lesson about seafloor spreading. It highlights the importance of understanding how to calculate the rate of seafloor spreading and recalls other concepts covered, such as the evidence from magnetic stripes and the geological processes involved. The paragraph serves as a conclusion to the lesson, reinforcing the learning objectives and providing a transition to the next lesson in the series.
Mindmap
Keywords
💡Continental Drift
💡Magnetic Stripes
💡Mid-Ocean Ridges
💡Seafloor Spreading
💡Subduction Zones
💡Lithospheric Plates
💡Polarities
💡Magma
💡Tectonic Plates
💡Pangaea
Highlights
Introduction to the concept of seafloor spreading theory.
Expectations for students to explain and simulate the zipper spreading process.
Calculation of the rate of seafloor spreading using magnetic loops.
Enumeration and explanation of evidences of seafloor spreading.
Importance of seafloor spreading relative to continental drift.
Recall of the past lesson on continental drift and Pangaea.
Evidences supporting the continental drift theory.
Challenges faced by Alfred Wegener's theory of continental drift.
Discovery of underwater features and mid-ocean ridges.
Harry Hess' proposal of seafloor spreading as a result of continental movement.
Materials and procedure for the seafloor spreading simulation activity.
Explanation of the role of mid-ocean ridges in lithospheric plate movement.
Process of new seafloor formation at mid-ocean ridges.
Description of processes occurring at the sides of the mid-ocean ridges.
Hess's support for Wegener's idea and the mechanism of continental breakup.
Evidence from molten material and magma erupting along ocean ridges.
Evidence from magnetic stripes and their alignment with the Earth's magnetic field.
Evidence from rock ages near and far from mid-ocean ridges.
Activity to calculate the rate of seafloor spreading using a magnetic field graph.
Summary of the seafloor spreading theory and its implications.
Transcripts
hello students today we are going to
discuss about the safety spreading
theory
in this lesson you are expected to
explain the zipper spreading theory
simulate and describe the zipper
spreading process
calculate the rate of safer spreading
using the magnetic loops
enumerate and explain the evidences of
citrus farting cutie and explain the
importance of safer spreading process
relative to the continental beef duty
but before we discuss the zipper
spreading theory
let's recall first our past lesson on
continental trip continental brief
theory states that all continents were
once one large landmass called pangaea
that broke apart and where the pieces
move slowly to their current locations
evidences of content and drift theory
includes the feet of the continents
fossil records of the prehistoric
organisms
similarities of rocks and mountain
ranges
and coal and glacial deposits
however
despite this evidences presented by
alfred wagner his idea on continental
grief was not accepted by his colleagues
because he failed to explain how the
drifting of the continents took place
this made scientists conduct further
studies in search for the answers
on how the continental drifting took
place with the advancement in modern
technologies and new techniques
scientists were able to gather
information and map the ocean floor
with the use of solar device and
submersibles scientists were able to
discover underwater features deep within
the ocean floor they found a system of
reaches or mountain ranges on the ocean
floor similar to those molten ranges on
the continents these are called the
mid-ocean ridges
one of the famous mid-ocean regions is
the mid-atlantic greens
in the early 1960s scientist harry has
proposed that the movement of the
continents was the result of safer
spreading
what is a sea for spreading
let's find out by doing a simulation
activity in this activity you will need
the following materials
board paper or you may make use of a
paper folder long size coupon ban pencil
pen or colored pencil
pair of scissors
paste or glue or sketch tape and ruler
please follow the procedure in the
activity
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so
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this
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now let's answer the guide questions in
the activity
what do the stripes in the paper
represent
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the stripes represent the rocks with
normal and reverse polarities
what does the middle slit represent
what occurs in this region
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the middle slate represents the mid
ocean greens where the actual seafarer
spreading occurs
what is the role of the mid-ocean weeds
in the movement of lithospheric plates
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the mid ocean reads is the origin of the
lithospheric movement
it is where the force that pushes the
little sphere originates
how does the new seafarer form at the
mid ocean winds
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hot less dense material below the
earth's grass rises towards the mid
ocean waves
as this material flows sideways
it creates a crop in the crust where
magma will flow out
this magma cools down and becomes the
new seafloor
what process or processes happen at the
side sleeves
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the side slits serve as abduction zone
where the old zipper plunges beneath
another tectonic plate is the earth
getting larger and wider when plates
drifted away from each other
explain briefly
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the earth is not getting larger or
smaller
if there is the production of a new
seafloor in the mid ocean rains
there is a destruction of old seafloor
at subduction zone
we now discuss the seafood spreading
theory as we have mentioned earlier that
in the early 1960s harry hess proposed
this theory
in 1962 he added a geologic processes to
account for wagner's continental drill
it was possible he said that magma from
beneath the earth's crust
could flow out between the tectonic
plates in the great global wave
as this magma cools it would expand and
push the plates on other side of it
where the north and south america move
to the west and eurasia and africa move
to the east
harry has probed wagner's idea was right
and clarified the mechanism that broke
the once joined continents into the
seven continents we know today
the continents are attached to the
plates so that when the plates move it
carried the continents with them
and this is the first evidence of the
safer spreading we call it the evidence
from molten material
magma erupting along with ocean wedges
cools down and hardened quickly forming
rock shape like pillows
separate spreading was strengthened with
the discovery that the magnetic rocks
near the reaches follow a magnetic
pattern look at this evidence the
evidence from magnetic stripes
as the molten rock hardened this
magnetic material inside the rock lined
up in the direction of the earth's
magnetic field
this forms unseen magnetic stripes
the magnetic poles reverse themselves
these stripes are mirror images on each
side of the mid ocean mix
another evidence of silver spreading is
the evidence found from draining some
points
has found out that those rocks near the
mid ocean ridges were younger while
those rocks found far away from mid
ocean ridges were older
now that you know and understand the
severe spreading theory
we try to find out how fast the sea
floor is spreading by doing the next
activity
in this activity you will need a
magnetic field graph
ruler calculator and pencil please
follow the procedure in this activity
shown here is the magnetic field graph
you will be working only with normal
polarity readings
these are the peaks above the baseline
on the top half of the graph
place the long ends of the ruler
vertically on the ground
then slide the ruler so that it lines up
with the center of pick one west of the
mid-atlantic leaves
determine and record the distance in
aids that line up with the center of the
one west
repeat this process or pick one east of
the rings
do the same for the remaining pairs of
normal polarity
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we summarize the answers in this day one
the rate of movement in centimeters per
year using the equation rate is equal to
distance divided by the time
for example for peak 1 west the time is
2 million years and the distance is 25
kilometers
calculate for the rate
rate is equal to distance which is 25
kilometers
divided by the time
2 million years
the rate is equal to 12.5 kilometers per
millimeter
to express the 12.5 kilometers per
million year to centimeters per year
we convert using the conversion factors
so the rate is equal to 12.5 kilometers
per million year times one mega year or
this is just equal to one million years
since mega is one times ten to the six
or one million times one thousand meters
over one kilometer
times one hundred cm over one meter
therefore the rate for peak one west is
equal to one point twenty five
centimeters per year please do the same
process for the rest of the given peaks
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do
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um
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so
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so
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so
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so
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so we now summarize the concepts we
discuss about safe ride spreading cutie
i hope you've learned how to calculate
the rate of zipper spreading and
remember other concepts we discuss in
this lesson so till next time in our
next lesson
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