Continental drift theory proposed that the continents were once joined together in a supercontinent called Pangaea. Wegener provided evidence like matching fossil and rock formations across continents, but his theory was rejected due to lacking an explanation for how the continents moved. Later studies of the seafloor using sonar revealed mid-ocean ridges where new crust was formed, explaining continental drift through the process of seafloor spreading and plate tectonics. Earthquake data showed seismic activity occurs at plate boundaries, confirming the Earth's surface is composed of shifting tectonic plates.
Earth and Life Science
Earth Materials and Processes
Deformation of the Crust: Continental Drift Theory
Learning Competencies
The learners shall be able to explain how the continents drift (S11/12ESId-20), and cite evidence that support continental drift (S11/12ES-Id-21).
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
1. Discuss the history behind the Theory of Continental Drift;
2. Describe the Continental Drift Theory; and
3. Enumerate and explain the evidence used to support the idea of drifting continents.
Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere.
Earth and Life Science
Earth Materials and Processes
Deformation of the Crust: Continental Drift Theory
Learning Competencies
The learners shall be able to explain how the continents drift (S11/12ESId-20), and cite evidence that support continental drift (S11/12ES-Id-21).
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
1. Discuss the history behind the Theory of Continental Drift;
2. Describe the Continental Drift Theory; and
3. Enumerate and explain the evidence used to support the idea of drifting continents.
Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere.
Download the lesson exemplar so you can follow this ppt. I have uploaded the lesson plan on this presentation too. Please search continental drift theory LP
if videos do not play, here are the links
https://www.youtube.com/watch?v=WaUk94AdXPA
https://www.youtube.com/watch?v=UwWWuttntio
Download the lesson exemplar so you can follow this ppt. I have uploaded the lesson plan on this presentation too. Please search continental drift theory LP
if videos do not play, here are the links
https://www.youtube.com/watch?v=WaUk94AdXPA
https://www.youtube.com/watch?v=UwWWuttntio
its about earth quake
Some plates have continents; some don't. All are in motion. Question: What evidence is there for these plate boundaries? Tectonic Plates ...
Study of plate tectonics of the earth, or plate movement, Jahangir Alam
a) Wegener’s Evidence (Continental Drift)
b) History of Plate Tectonics
c) Breakup and Appearence of Pangea
WHAT IS A PLATE?
Major continental and oceanic plates include:
Types of Earth’s Crust:
Plate tectonics (from the Late Latin tectonicus) is a scientific theory which describes the large scale motions of Earth's lithosphere.
THE DYNAMIC EARTH:
The earth is a dynamic planet, continuously changing both externally and internally. The earth’s surface is constantly being changed by endo-genetic processes resulting in volcanism and tectonism, and exogenetic processes such as erosion and deposition. These processes have been active throughout geological history. The processes that change the surface feature are normally very slow (erosion and deposition) except some catastrophic changes that occur instantaneously as in the case of volcanism or earthquakes. The interior of the earth is also in motion. Deeper inside the earth, the liquid core probably flows at a geologically rapid rate of a few tenths of mm/s. Several hypotheses attempted to explain the dynamism of the earth.
+ Horizontal movement hypothesis
+ Continental drift, displacement hypothesis
Development of the plate tectonic theory.
Plate tectonic theory arose out of the hypothesis of continental drift proposed by Alfred Wegener in 1912. He suggested that the present continents once formed a single land mass that drifted apart, thus releasing the continents from the Earth's core and likening them to "icebergs" of low density granite floating on a sea of denser basalt.
Seafloor Spreading
The first evidence that the lithospheric plates did move came with the discovery of variable magnetic field direction in rocks of differing ages.
Plate Tectonics
Chapter 19
Plate Tectonics
• Plate tectonics - Earth’s surface composed thick plates that move
• Intense geologic activity is concentrated at plate boundaries
• Combination of continental drift and seafloor spreading hypotheses
proposed in late 1960s
Review: Three Types of Plate Boundaries
Transform Convergent Divergent
(strike-slip) (subduction) (spreading)
But how do we
know that plates
move at all ?
Early Case for Continental Drift
• Puzzle-piece fit of
coastlines of Africa and
South America has long
been known
•In early 1900s, Alfred Wegner noted South America, Africa, India,
Antarctica, and Australia have almost identical rocks and fossils
Early Case for Continental Drift
– Glossopteris (plant),
Lystrosaurus and
Cynognathus (animals)
fossils found on all five
continents
– Mesosaurus (reptile)
fossils found in Brazil and
South Africa only
Glaciers
• Most of the Earth's ice is found in Antarctic continental glacier.
• Where are some other continental glaciers ?
• Glacial striations on a
rock from stones grinding at
the base of a heavy ice sheet
leave these shiny linear
marks on the bedrock below.
Glacial Characteristics
• Glaciers flow downhill as a solid mass that creates channels, and
walls made of ground up rock debris known as a merraine.
Erosional Landscapes
• Erosional landforms produced by
valley glaciers include:
– U-shaped valleys
– Hanging valleys
• Smaller tributary glacial valleys
left stranded above more
quickly eroded central valleys
Early Case for Continental Drift
• Wegner reassembled continents into
the supercontinent Pangaea
• Late Paleozoic glaciation patterns on
southern continents best explained by
their reconstruction into (Pangaea)
Gondwanaland
Early Case for Continental Drift
• Coal beds of North America and Europe
indicate Laurasia super continent
• Continental Drift hypothesis initially
rejected
– Wegener could not come up with viable
driving force
– continents should not be able to “plow
through” sea floor rocks
The Earth's Magnetic Field
Can Give Us Clues
Paleomagnetism and Continental Drift Revived
• Studies of rock magnetism allowed
determination of magnetic pole
locations (close to geographic poles)
• Paleomagnetism uses mineral
magnetic alignment and dip angle to
determine the distance to the
magnetic pole when rocks formed
– Steeper dip angles indicate rocks formed
closer to the magnetic poles
• Rocks with increasing age point to
pole locations increasingly far from
present magnetic pole positions
Paleomagnetism and
Continental Drift Revived
• Apparent polar wander curves
for different continents suggested
plate movement !
• Wegner was right!
* Earthquakes .
2. Continental Drift TheoryContinental Drift Theory
• First proposed by Alfred Wegener in 1912:
– 250 million years ago, all of the continents
were combined into one super-continent
called “Pangaea”
– The continents gradually drifted apart to
where they are today
• Wegner didn’t make up this theory out of
the blue – like all scientists, he based it on
evidence
3. Evidence SummaryEvidence Summary
• Geographic fit of South America and
Africa
• Fossils match across oceans
• Rock types and structures match across
oceans
• Ancient glacial features
4. Geographic FitGeographic Fit
• Continents look like
they could be part
of a giant jigsaw
puzzle
• Here’s how they moved apart
6. Fossil Fuel in AntarcticaFossil Fuel in Antarctica
• Tropical plant remains (coal deposits) found in
Antarctica
– this is evidence that Antarctica was once much warmer
and much closer to the equator, since tropical plants
don’t grow in Antarctica today
7. Rock Structures Match Across OceansRock Structures Match Across Oceans
• Same rock patterns found in South America,
India, Africa, Antarctica and Australia
11. Evidence but no MethodEvidence but no Method
• While Wegener presented compelling
evidence, there was still no explanation for
HOW the continents drifted.
• The question remained: “If continents drift,
what is making them move?”
12. Sea Floor DiscoveriesSea Floor Discoveries
• WW II: Military Spending
• U.S. Navy mapped seafloor with sonar in
order to help ships and submarines
navigate.
• They expected to find that the ocean floor
was a vast, flat plain. What they found was
shocking.
13. Sea Floor DiscoveriesSea Floor Discoveries
• Instead of miles and miles of flat surface,
they found that the ocean floor had:
– oceanic ridges - submerged mountain ranges
– fracture zones - cracks perpendicular to ridge
– trenches - narrow, deep gashes
– seamounts - drowned undersea islands
14. Sea Floor DiscoveriesSea Floor Discoveries
• In addition, they discovered that the rocks of the
seafloor included only basalt, gabbro, and
serpentinite - no continental materials.
• This suggested that the sea floor was not simply
“covered up” continental crust, but was made of
different materials and at a different time
15. Sea Floor DiscoveriesSea Floor Discoveries
• Further study of these rocks led scientists
to even more surprising information:
• The sea floor’s youngest rocks were
located right at the ocean ridge – and as
you moved away from the ridge in either
direction, the rocks got progressively
older.
17. Sea Floor DiscoveriesSea Floor Discoveries
• What scientists discovered was that the sea floor was
being constantly “recycled.” The youngest rocks were
created from magma rising to the surface, hardening and
pushing aside the older rock.
• Scientists called this process “sea floor spreading.”
18. Sea Floor DiscoveriesSea Floor Discoveries
• So now we know:
– sea floor is being created at the mid-
ocean ridges
– sea floor is spreading
– the oldest ocean floor occurs at the
coastlines of continents…
• Why doesn’t the earth get
bigger? Where does the
ocean floor go? Why
doesn’t it get any older?
19. Sea Floor DiscoveriesSea Floor Discoveries
• The ocean floor is pushed against the
continental crust – and because it is
denser, it dives under the crust.
• This process is
called
subduction
21. The Rise of Plate TectonicsThe Rise of Plate Tectonics
• In the late 1950’s, the United States was
engaged in The Cold War with the Soviets
• To keep an eye on Soviet nuclear tests, the
U.S. military developed new, advanced
seismometers
• These seismometers were deployed in over 40
allied countries and were recording 24 hrs/day,
365 days/year
22. The Rise of Plate TectonicsThe Rise of Plate Tectonics
• Besides nuclear tests, the seismometers
recorded every moderate to large earthquake
on the planet.
• Scientists mapped the earthquake data and
found something they weren’t expecting:
– Armed with this high-precision earthquake data,
seismologists found that activity happens in narrow
bands.
23. The Rise of Plate TectonicsThe Rise of Plate Tectonics
24. The Rise of Plate TectonicsThe Rise of Plate Tectonics
• The discovery of these bands led scientists to
understand that the earth’s outer shell is broken
into thin, curved plates that move laterally atop
a weaker underlying layer.
• Think of it like a hard-boiled egg: you can put
cracks all over the shell of a hard-boiled egg,
but the egg is still “whole”
25. Types of Plate BoundariesTypes of Plate Boundaries
• The interaction of the plate edges with each other
can be classified as one of three main types of
boundaries:
• Convergent boundaries
• Divergent boundaries
• Transform boundaries
26. Types of Plate BoundariesTypes of Plate Boundaries
• Convergent: areas of plates that are moving
toward each other
– there are three sub-types of convergent boundaries:
• oceanic to continental
• continental to continental
• oceanic to oceanic
27. Types of Plate BoundariesTypes of Plate Boundaries
• Divergent: areas of plates that are moving away
from each other
28. Types of Plate BoundariesTypes of Plate Boundaries
• Transform: areas of plates that are sliding past
each other
29. Types of Plate BoundariesTypes of Plate Boundaries
• Here’s an animation of each type of plate boundary
33. Continental Drift 1 ptContinental Drift 1 pt
• The scientist who first proposed the
theory of continental drift
34. Continental Drift 1 pt AnswerContinental Drift 1 pt Answer
• Who was Alfred Wegner?
35. Continental Drift 2 ptContinental Drift 2 pt
• fossils match across continents and
oceans, same rock patterns found on
five different continents, mountain
ranges match across the Atlantic
ocean
36. Continental Drift 2 pt AnswerContinental Drift 2 pt Answer
• What is some of the evidence
Wegner used to support his theory
that the continents were once joined?
37. Continental Drift 3 ptContinental Drift 3 pt
• Because he had no answer to the
question, “If the continents are
drifting, what mechanism is causing
them to move?”
38. Continental Drift 3 pt AnswerContinental Drift 3 pt Answer
• Why was Wegner’s theory of
continental drift widely ignored?
40. Sea Floor 1 pt AnswerSea Floor 1 pt Answer
• What did Harry Hess and the US Navy
discover when they mapped the sea floor
using sonar?
41. Sea Floor 2 ptSea Floor 2 pt
• The process of ocean crust “diving” under
other crust into the mantle
42. Sea Floor 2 pt AnswerSea Floor 2 pt Answer
• What is subduction?
43. Sea Floor 3 ptSea Floor 3 pt
• The process by which the newest ocean
floor is created at mid-ocean ridges,
pushing older crust outward
44. Sea Floor 3 pt AnswerSea Floor 3 pt Answer
• What is sea floor spreading?
45. Plate Tectonics 1 ptPlate Tectonics 1 pt
• What the earth’s outer shell is broken into
46. Plate Tectonics 1 pt AnswerPlate Tectonics 1 pt Answer
• What are plates?
47. Plate Tectonics 2 ptPlate Tectonics 2 pt
• Instrument deployed by US Military to spy
on soviet nuclear tests which also detected
medium-to-large earthquakes.
48. Plate Tectonics 2 pt AnswerPlate Tectonics 2 pt Answer
• What is a seismometer?
49. Plate Tectonics 3 ptPlate Tectonics 3 pt
• The three ways plate boundaries interact
50. Plate Tectonics 3 pt AnswerPlate Tectonics 3 pt Answer
• What are convergent, divergent, &
transform?
51. Review – Exit SlipReview – Exit Slip
• Choose what you believe to be the strongest piece of
evidence Wegner uncovered to support the idea of
continental drift and explain why you think it is the most
convincing.
• If new sea floor is constantly being created, why isn’t the
earth growing in size?
• How did earthquakes help scientists to understand the
structure of the earth’s crust?