Continental
Drift
Pangaea
Continental Drift
Seafloor Spreading
Plate Tectonics
Plate
Lithosphere
Asthenosphere
Convection Currents
Alfred Wegener
German
meteorologist who
proposed the theory
of Continental Drift
He thought that the
puzzle like fit of the
continents was not
just a coincidence
Continental Drift
 According to Wegener’s
hypothesis, the
continents have moved
slowly to their current
locations
 Wegener suggested that
all continents once were
connected as one
landmass that broke
apart about 200 million
years ago
 He called this large
landmass Pangaea
A Controversial Idea
Wegener’s ideas of continental drift were
controversial.
It wasn’t until long after his death that his
basic ideas about continental drift were
accepted.
Other scientists of that time disagreed with
Wegener’s hypothesis. They said that
continental drift would not be necessary to
explain Wegener’s observations.
A Controversial Idea
Why?
He was unable to explain
exactly how the continents
drift apart.
His theory was that the
continents plowed through
the ocean floor and were
driven by the spin of the
Earth.
How could continents drift?
Although Wegener provided evidence to
support his hypothesis of continental drift,
he couldn’t explain how, when, or why
these changes took place.
Because other scientists could not provide
explanations either, Wegener’s idea of
continental drift was initially rejected.
Rock, fossil, and climate clues were the
main types of evidence for continental
drift.
How could continents drift?
After Wegener’s death, more clues were
found, largely because of advances in
technology, and new ideas that related
to continental drift were developed.
Play first 4 minutes of Eye of Nye
(play youtube.com of Alfred Wegener song)
Quick Questions
What are some things that make the theory
of Continental drift difficult to accept?
As you read, see how your ideas compare
with people who first heard the theory.
Why was the scientific community
dissatisfied with the theory of continental
drift?
A Closer Look at Evidence Activity
 Get Worksheet with the Five Continents detached.
FIRST STEP:
Need 5 colors to color the 5 different Fossil
Record Evidence found on each continent.
SECOND STEP: Color the Coast Lines(dotted) a shade of Blue
THIRD STEP: Color the continent land a shade of green.
FOURTH STEP: Cut out continents (LEAVE COASTLINE
ATTACHED)
and fit it together like a puzzle.
The fossil records should fit together!
Glue down on page 13 if you know it is correct!
Evidence: Animal Fossils
Fossils found in different parts of the
world supported continental drift.
Fossils of the reptile Mesosaurus have
been found in South America and Africa.
Evidence: Plant Fossils
Fossils of plants also
support continental drift.
The plant Glossopteris has been found
on 5 separate land masses (Africa,
Australia, India, South America, and
Antarctica).
The appearance of this plant on so
many different continents also support
Wegener’s idea that were once
connected and had similar climates
Evidence: Climate
Glacial deposits and rock surfaces
scoured and polished by glaciers are
found in several land masses. (South
America, Africa, India, and Australia).
This shows that parts of these
continents were covered with glaciers in
the past.
PAGE 184
Evidence: Rock Sequences
Similar rock structures are found on
different continents.
Parts of the Appalachian Mountains
of the eastern United States are
similar to those found in Greenland
and western Europe.
PAGE 184
YouTube Video
“Continental Drift”
Michael Sammartano
11:56
Afterwards: Cloze Activity Fill in blank worksheet. “Continental Drift”
Exit Slip
1. Who was the person who came up
with the hypothesis of Continental
Drift?
2. What was the large landmass called?
3. Name three different types of
evidence that supports Continental Drift.
4. Why was the theory controversial in
its time?
What question do
we still have after
all of Alfred Wegener’s
Evidence?
HOW did the
Continents Drift?
HOW do continents drift?
Plates move due to
1. Sea-Floor Spreading
and because of
2. Convection Currents
in the mantle.
Sea-Floor Spreading
Sea-Floor Spreading
Discovered by Harry Hess
Harry Hess
1906–1969
American Geologist
While on duty with the US
Naval Reserve, he discovered
flat-topped seamounts using
echo sounders on his ship.
He described the oceans as
young and with constant
renewal by magma flowing
into the mid-ocean ridges. In
this he described the seafloor spreading process.
Discovered Sea-Floor
Spreading by using:
Sonar - a device that
bounces sound waves
off under-water
objects and then
records the echoes of
these sound waves.
*The time it takes for
the echo to arrive
indicates the distance
to the object.
Harry Hess
Princeton grad. Geologist
Navy Captain during WWII
Conducted sonar mapping
of sea floor while traveling from
battle to battle during the
Island-hopping campaign in the
Pacific during World War II.
Sonar is Sound waves that bounce off the
ocean floor, and then back to the
sonar recording device on the ship to tell
seafloor depth.
Ocean Floor Map
In 1952, Marie Tharp developed the first
chart of the Mid-Atlantic Ridge System.
Later, with Bruce Hoezen, they complied a map of
the Global Ridge System.
Advances in SONAR and SUBMARINE
technology in the 1950's and 1960's
allowed scientists to understand
what was happening on the Ocean Floor.
The Mid-Ocean Ridge System
R
Above: The Global Mid-Oceanic Ridge System
(Analogy: The Mid-Ocean Ridges are like the seams on a baseball.)
The Mid-Atlantic Ridge
Mid-Atlantic Ridge – the longest chain
of mountains in the world---these are
divergent plate boundaries.
Harry Hess
after studying the maps of the
ocean floor, he developed a theory
that new ocean crust forming and
spreading laterally at Mid-ocean
ridge called SEA FLOOR
SPREADING
Sea-Floor Spreading
Ocean floor moves like a
conveyor belt carrying
continents with it.
New ocean floor forms along
cracks in the ocean crust as
molten material erupts from the
mantle spreading out and
pushing older rocks to the sides
of the crack.
Sea-Floor Spreading
* the process
that continually
adds new
material to the
ocean floor while
pushing older
rocks away from
the ridge
The Eye of Nye (11 minutes) 4 minutes on Alfred Wegener end Harry Hess
YouTube Video 4:19
Alfred Wegener vs. The Fixists (Continental Drift) –
Science History Battle Rap
Sea-Floor Spreading
Evidence
1.Molten Rock
Material –
Rocks shaped like
pillows(rock pillows)
show that molten
material has erupted
again and again from
cracks along the
mid-ocean ridge and
cooled quickly
Sea-Floor Spreading
Evidence
2. Magnetic Strips – Rocks that make up the
ocean floor lie in a pattern of magnetized stripes
which hold a record of the reversals in Earth’s
magnetic field
Sea-Floor Spreading
Sea-Floor Spreading
Evidence
3. Drilling Rock
Core Samples –
Core samples from
the ocean floor
show that older
rocks are found
farther from the
ridge; youngest
rocks are in the
center of the
ridge
Sea-Floor Spreading
Evidence 4. Iceland
Growing
larger every
year due to
volcanic
activity.
Iceland Landscape
Iceland Landscape
Iceland Landscape
Iceland Landscape
If the Sea-Floor is
Spreading..Why doesn’t
Planet Earth Get Bigger?
Subduction – Process by
which the ocean floor sinks
beneath a deep-ocean
trench and back into the
mantle; allows part of the
ocean floor to sink back into
the mantle
Why is the sea
floor spreading
apart?
Answer:
Convection
Currents in the
Mantle are causing
Oceanic Crust to
Separate.
Continents Adrift Video
26 minutes
Needs to be after SeaFloor Spreading and Convergent and Divergent Boundaries!!
Continents Adrift
Video Quiz
Number your paper to 9
1. Which of these is NOT
used as evidence that Earth’s
surface consists of plates that
are in continuous motion?
A.
B.
C.
D.
Earthquakes
Blizzards
Mountains
Volcanoes
2. What did scientist Alfred
Wegener call the largest
supercontinent that once
existed?
A.
B.
C.
D.
Eurasia
Panamerica
Pangaea
Ring of Fire
3. Which of these pieces of
evidence did Wegener use
to support his theory of
continental drift?
A.
B.
C.
D.

Subduction Zones
Divergent Boundaries
Seafloor Spreading
Fossils from Different
Countries
4. Seafloor spreading explains
why….?
A. Materials circulate within the Earth’s
Mantle.
B. The ocean has high and low tides.
C. One portion of the Earth’s crust
dives beneath another portion.
D. The oldest part of the ocean floor is
found farthest from the mid-ocean
ridge.
5. Scientists think that
tectonic plates can move
when…..?
A. Materials circulate in the Earth’s
mantle.
B. High tide occurs.
C. Magma is released from the
mid-ocean ridge.
D. The lithosphere begins to melt.
6. The rock outer layer of
the Earth is called the?
A.
B.
C.
D.
Mantle
Atmosphere
Hydrosphere
Lithosphere
7. Energy released during an
earthquake creates?
A.
B.
C.
D.
An overheated inner core.
A mid-ocean ridge
An eruption of molten lava
A seismic wave
8. The Ring of Fire refers to?
A. An active erupting volcano.
B. The volcanoes surrounding
the Pacific Ocean.
C. The spreading that takes
place on the ocean floor.
D. The land once known as
Pangaea.
9. Mountains on the Earth’s
surface form in random
locations, with no relation to
the Earth’s Plates?
A. TRUE
B. FALSE