Alfred Wegener first proposed the theory of continental drift in the early 20th century, which hypothesized that the continents were once joined together in a supercontinent called Pangaea before drifting apart. Wegener's theory was rejected by scientists at the time because he could not explain the mechanism driving continental movement. The development of the theory of plate tectonics in the 1940s provided evidence that continents move due to interactions between tectonic plates, validating Wegener's original hypothesis.
Steps to Plate TectonicsStep 1 – Continental Driftwww.mat.docxdessiechisomjj4
Steps to Plate Tectonics:
Step 1 – Continental Drift
www.math.montana.edu / ~nmp / materials / ess / geosphere / inter / activities / plate_calc / pangaea_map.gif
The Continental Drift hypothesis published by Alfred Wegener in his 1915 book “ The Origin of Continents and Oceans”, although this was partially based on the work of earlier investigators.
Continental Drift = the continents were once connected in a single supercontinent called Pangaea. They have since drifted apart and are still moving today.
http://www.kidsgeo.com/geology-for-kids/0042-pangaea.php
Wegener’s hypothesis had several problems:
1) He had no power source – no way to make the continents move.
2) He thought the continents moved through the seafloor just like boats move through the ocean, but there was no evidence of this (no wake)
3) He was a meteorologist so many geologists didn’t take him seriously!
BUT Wegener had lots of evidence to show that the continents were once connected!
1) The jigsaw puzzle-like fit of the continents.
Figure 2.3 in text
Identical fossil assemblages on now widely spaced continents!
best about 250-200 MY ago
become increasingly dissimilar the closer to today we look!
Garrison, 2012, Essentials of Oceanography
3) Sequences of similar rock types on continents which do not now have the same geologic environment!
http://www.geology.ohio-state.edu/~vonfrese/gs100/lect25/index.html
4) Geologic structures (mountain ranges, faults, chains of volcanoes) which match up on either side of oceans but can not be found underwater.
5) Apparent polar wander – paleoclimatic evidence the continents had very different climates 250 MY ago than they do today.
either the continents moved or
the climate bands moved – which means the Earth’s poles of rotation moved.
Earth’s climate zones today are arranged symmetrically around the poles.
http://www.webquest.hawaii.edu/kahihi/sciencedictionary/C/climatezone.php
Paleoclimatic data from ˶300 MY ago, figure 2.5 in text
After Wegener died, his ideas were largely dismissed, until…
Post-Wegener evidence for drifting continents (and plate tectonics)…
6) Apparent Polar Wander – Paleomagnetic evidence.
Figure 2.7 showing that the Earth has a magnetic field very similar to that created by a bar magnet.
Directions of magnets parallel to Earth’s magnetic field lines.
Post-Wegener evidence for drifting continents (and plate tectonics)…
Figure 2.7b showing how magnets align to the Earth’s magnetic field when allowed to move freely.
Rocks containing the mineral magnetite (especially basalt) record the orientation of the Earth’s magnetic field at the time the rocks formed.
Figure 2.8a showing apparent polar wander paths for Europe and North America.
Figure 2.8b showing alignment of polar wander curves if the Atlantic Ocean is “closed”
The polar wander tracks for all the continents show great variation, suggesting it is the continents that moved!
If we put the continents “back to.
This pdf covers theory of continental drift and plate tectonics.
Continental drift
Plate Tectonics
Mantle Convection
Convection currects
Types of Mantle convection
Drivers of the plate motion.
Bibliography_ Lutgens, Tarbuk and Tasa Publisher: Prentice Hall
Plate Tectonics
Chapter 19
Plate TectonicsPlate tectonics - Earth’s surface composed thick plates that moveIntense geologic activity is concentrated at plate boundariesCombination of continental drift and seafloor spreading hypotheses proposed in late 1960s
Review: Three Types of Plate Boundaries
But how do we
know that plates
move at all ?
Transform Convergent Divergent
(strike-slip) (subduction) (spreading)
Early Case for Continental DriftPuzzle-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 DriftGlossopteris (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 ?
FIGURE 10.5 Iceberg calving at Wrangell-St. Elias National Park, Alaska. Calving occurs when huge blocks of ice break off at the edge of a glacier that has moved to a shoreline. [Tom Bean.]
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.
FIGURE 10.18 Glacial striations on bedrock in Glacier Bay National Park, Alaska. Striations are evidence of the direction of ice movement and are especially important clues for reconstructing the movement of continental glaciers. [Carr Clifton.]
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 LandscapesErosional landforms produced by valley glaciers include: U-shaped valleys Hanging valleysSmaller tributary glacial valleys left stranded above more quickly eroded central valleys
Early Case for Continental DriftWegner 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 DriftCoal 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 RevivedStudies 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 formedSteeper dip angles indicate rocks formed closer .
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Human activities, particularly fossil fuel combustion and deforestation, have significantly altered the natural carbon cycle, leading to increased atmospheric carbon dioxide concentrations and driving climate change. Understanding the intricacies of the carbon cycle is essential for assessing the impacts of these changes and developing effective mitigation strategies.
By studying the carbon cycle, scientists can identify carbon sources and sinks, measure carbon fluxes, and predict future trends. This knowledge is crucial for crafting policies aimed at reducing carbon emissions, enhancing carbon storage, and promoting sustainable practices. The carbon cycle's interplay with climate systems, ecosystems, and human activities underscores its importance in maintaining a stable and healthy planet.
In-depth exploration of the carbon cycle reveals the delicate balance required to sustain life and the urgent need to address anthropogenic influences. Through research, education, and policy, we can work towards restoring equilibrium in the carbon cycle and ensuring a sustainable future for generations to come.
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Steps to Plate TectonicsStep 1 – Continental Driftwww.mat.docxdessiechisomjj4
Steps to Plate Tectonics:
Step 1 – Continental Drift
www.math.montana.edu / ~nmp / materials / ess / geosphere / inter / activities / plate_calc / pangaea_map.gif
The Continental Drift hypothesis published by Alfred Wegener in his 1915 book “ The Origin of Continents and Oceans”, although this was partially based on the work of earlier investigators.
Continental Drift = the continents were once connected in a single supercontinent called Pangaea. They have since drifted apart and are still moving today.
http://www.kidsgeo.com/geology-for-kids/0042-pangaea.php
Wegener’s hypothesis had several problems:
1) He had no power source – no way to make the continents move.
2) He thought the continents moved through the seafloor just like boats move through the ocean, but there was no evidence of this (no wake)
3) He was a meteorologist so many geologists didn’t take him seriously!
BUT Wegener had lots of evidence to show that the continents were once connected!
1) The jigsaw puzzle-like fit of the continents.
Figure 2.3 in text
Identical fossil assemblages on now widely spaced continents!
best about 250-200 MY ago
become increasingly dissimilar the closer to today we look!
Garrison, 2012, Essentials of Oceanography
3) Sequences of similar rock types on continents which do not now have the same geologic environment!
http://www.geology.ohio-state.edu/~vonfrese/gs100/lect25/index.html
4) Geologic structures (mountain ranges, faults, chains of volcanoes) which match up on either side of oceans but can not be found underwater.
5) Apparent polar wander – paleoclimatic evidence the continents had very different climates 250 MY ago than they do today.
either the continents moved or
the climate bands moved – which means the Earth’s poles of rotation moved.
Earth’s climate zones today are arranged symmetrically around the poles.
http://www.webquest.hawaii.edu/kahihi/sciencedictionary/C/climatezone.php
Paleoclimatic data from ˶300 MY ago, figure 2.5 in text
After Wegener died, his ideas were largely dismissed, until…
Post-Wegener evidence for drifting continents (and plate tectonics)…
6) Apparent Polar Wander – Paleomagnetic evidence.
Figure 2.7 showing that the Earth has a magnetic field very similar to that created by a bar magnet.
Directions of magnets parallel to Earth’s magnetic field lines.
Post-Wegener evidence for drifting continents (and plate tectonics)…
Figure 2.7b showing how magnets align to the Earth’s magnetic field when allowed to move freely.
Rocks containing the mineral magnetite (especially basalt) record the orientation of the Earth’s magnetic field at the time the rocks formed.
Figure 2.8a showing apparent polar wander paths for Europe and North America.
Figure 2.8b showing alignment of polar wander curves if the Atlantic Ocean is “closed”
The polar wander tracks for all the continents show great variation, suggesting it is the continents that moved!
If we put the continents “back to.
This pdf covers theory of continental drift and plate tectonics.
Continental drift
Plate Tectonics
Mantle Convection
Convection currects
Types of Mantle convection
Drivers of the plate motion.
Bibliography_ Lutgens, Tarbuk and Tasa Publisher: Prentice Hall
Plate Tectonics
Chapter 19
Plate TectonicsPlate tectonics - Earth’s surface composed thick plates that moveIntense geologic activity is concentrated at plate boundariesCombination of continental drift and seafloor spreading hypotheses proposed in late 1960s
Review: Three Types of Plate Boundaries
But how do we
know that plates
move at all ?
Transform Convergent Divergent
(strike-slip) (subduction) (spreading)
Early Case for Continental DriftPuzzle-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 DriftGlossopteris (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 ?
FIGURE 10.5 Iceberg calving at Wrangell-St. Elias National Park, Alaska. Calving occurs when huge blocks of ice break off at the edge of a glacier that has moved to a shoreline. [Tom Bean.]
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.
FIGURE 10.18 Glacial striations on bedrock in Glacier Bay National Park, Alaska. Striations are evidence of the direction of ice movement and are especially important clues for reconstructing the movement of continental glaciers. [Carr Clifton.]
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 LandscapesErosional landforms produced by valley glaciers include: U-shaped valleys Hanging valleysSmaller tributary glacial valleys left stranded above more quickly eroded central valleys
Early Case for Continental DriftWegner 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 DriftCoal 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 RevivedStudies 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 formedSteeper dip angles indicate rocks formed closer .
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Human activities, particularly fossil fuel combustion and deforestation, have significantly altered the natural carbon cycle, leading to increased atmospheric carbon dioxide concentrations and driving climate change. Understanding the intricacies of the carbon cycle is essential for assessing the impacts of these changes and developing effective mitigation strategies.
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4. Continental drift was Wegener’s theory
that all continents had once been joined
together in a single landmass and have
drifted apart since.
Wegener named this supercontinent
Pangaea.
Wegener’s theory was rejected by
scientists because he could not explain
what force pushes or pulls continents.
Continental drift video clip
5.
6. Fit of Continents
Across the Atlantic
Mountain ranges in
South America line
up exactly with
those in Africa!
7. Notice how fossils lined up across continents!
http://evolution.berkeley.edu/evolibrary/images/history/fossils3.gif
8. Amazing Facts: Did you know...
...that India was once in the Southern Hemisphere
connected to Antarctica?
...that North America was once surrounded by warm,
tropical seas?
...that Africa was once covered by glaciers, which were
kilometers in thickness?
...that the Sahara desert was once a tropical rain forest?
9. As North America has drifted to different latitudes,
changing climates were experienced. This shows the
changes in the state of New Mexico.
An example of the proof for changing climate:
At one time,
the area that
is New
Mexico was
below the
equator!
10. He could not find the force that was
causing the continents to drift.
Because of this, he could not convince
anyone that continents could move.
He died in Greenland on an expedition.
At the time of his death, no one believed
his hypothesis!
Technology developed during the 1940’s
changed all that!
12. As the sea floor spreads, the lava cools according to the
magnetic poles at the time. The rocks on the ocean
floor have proved that the earth’s magnetic field
sometimes reverses. The inner core flips and so the
north pole moves to the southern hemisphere! The
earth itself does not flip.
http://platetectonics.pwnet.org/img/blocks.gif
16. The place where two plates move
apart or diverge is called a divergent
boundary.
17. This is a model of sea floor spreading at a divergent
boundary called a mid ocean ridge.
18. Did you know that the Earth’s longest mountain range is
underwater and is called the mid-ocean ridge?
: www.ocean.udel.edu
The Mid-Ocean Ridge system, shown above snaking its way
between the continents, is more than 56,000 kilometers (35,000 mi)
long. It circles the earth like the stitching on a baseball!
19. A convergent boundary is where two plates
come together, or converge. The result of the
plates hitting together is called a collision.
20. A transform boundary is a place where
two plates slip past each other, moving in
opposite directions.
24. Because one plate gets pushed under
another, it is called subduction. This
is where volcanoes form!
Oceanic crust
colliding with
oceanic crust
Oceanic crust colliding
with continental crust
all from: http://www.geo.lsa.umich.edu/~crlb/COURSES/270
25. The process by
which the ocean
floor sinks
beneath a deep-
ocean trench
and back into
the mantle is
called
26. Plate tectonics video clip
Here is a great link for seeing where each type of
boundary is located.
Click here for a great hyperlink! Make sure you
click on each type of boundary in the key!
