Evidence for a Changing Earth
PART 1
Chapter 1 Section 3
Drifting Continents
How does the earth change?
http://science.discovery.com/tv-shows/greatestdiscoveries/videos/100-greatest-discoveriescontinental-drift.htm
video by Bill Nye 100 Greatest Discoveries.
Wegener’s Pangaea
http://www.platetectonics.com/book/page_7.asp
Evidence for Continental Drift

Glossopteris fossils- woody fern-like
trees from 250 million years ago. Found
across continents.
Evidence for Continental Drift

Lystrosaurus fossils-(meaning "shovel lizard")
Lystrosaurus was a heavily-built, mammal like
reptile with a short, stubby tail. Instead of teeth
it had two tusk-like fangs made of horn. It was a
plant-eater about 3 feet (1 m) long and about
200 pounds. It lived in herds near lakes and
swamps. Since fossils of Lystrosaurus had been
found in South Africa, India, Europe, and Asia,
finding Lystrosaurus fossils in Antartica was
further evidence that the continents were once
connected into one large continent.
Lystrosaurus
Evidence for Continental Drift

Mesosaurus fossils- Wegener found
Mesosaurus fossils in Africa and South America.
It was a major piece of evidence to support his
theory of continental drift. Since the
Mesosaurus was a fresh water reptile, there was
no way it could have swam across the Atlantic
Ocean (which has salt water) to both
continents. So it provided evidence that Africa
and South America were at one point joined
together.
http://wiki.answers.com/Q/Where_did_Alfred_wegener_find_fossils_of_mesosaurus#ixzz1aVA2RgLd
Mesosaurus
Continental Drift

http://www.youtube.com/watch?v=WaUk94AdXPA&feature=related

http://www.youtube.com/watch?v=Cm5giPd5Uro

In 1910, Alfred Wegener proposed the theory of
continental drift. He believed that the continents were
drifting apart. He found evidence to prove his theory.
But he could not answer one question. How were the
continents moving? He thought they were plowing
through the ocean crust. Other scientists knew this
could not happen and so discredited his theory.

http://wgvu.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.wegener1
/plate-tectonics-the-scientist-behind-the-theory/Historical snapshot about
Alfred Wegener.
Three pieces of Evidence for
Continental Drift Theory

1.

2.

3.
Alfred Wegener Song By The Amoeba
People

http://www.youtube.com/watch?v=T1cES1Ekto&feature=related
Evidence for a Changing Earth
PART 2
Chapter 1 Section 4
Sea-floor Spreading
Sea-floor Spreading

In the 1960's scientists finally found what
was missing in Wegener's theory.
Geologist Harry Hess finally found
evidence that Wegener was right when
mountains were discovered at the bottom
of the ocean. Hess proposed his theory of
sea-floor spreading as the answer to the
mystery of continental drift.
Discovery of Underwater
Mountains
 The mid-ocean ridge is found throughout the
oceans of the earth. This is a 50,000 mile chain
of volcanic mountains in the middle of the
ocean.
 These mountains have a deep crack that runs
through them. It is called a rift valley.
 Sea-floor spreading happens here as molten
magma from the mantle oozes up and forms
new ocean floor spreading the plates apart. It is
a slow, regular process. There are no explosive
bursts like volcanic eruptions on land.
Mid-Ocean Ridge
“Sea Floor Spreading with Bill Nye”
http://www.youtube.com/watch?v=GyMLlLxbfa4&feature=related
Evidence for Sea-floor Spreading
 During
WWII Geologist Harry
Hess worked on a ship that had
sonar. They mapped the ocean
floor and discovered the “MidAtlantic Ridge”. Prior to this all
scientists believed the Oceans
floor was flat and barren.
Evidence for Sea-floor Spreading
The mid-ocean ridges occur along plate
boundaries that are separating (diverging).
 Rocks that form from molten rock , called
“Pillow Lava” were discovered along the midocean ridge by the submersible submarine
named Alvin.

Evidence for Sea-floor Spreading

Core samples drilled and collected from the
Atlantic ocean floor showed that the sediment
was thinner near the mid-ocean ridges and the
age of the rock was younger meaning the ocean
floor was younger at the mid-ocean ridge.
Core Sampling Model
Use the straw at your group’s station and
carefully push it down into the cup on
your table. ONLY ONE TIME! BE
CAREFUL. DO NOT TIP OVER!!
 Put your finger over the top and very
gently and slowly pull up a core sample.
 Each person should draw a diagram of
your sample.
 Question: What did scientists learn from
core samples to support the theory of
sea-floor spreading?

Evidence for Sea-floor Spreading

Those core samples
also showed a record
of magnetic reversals.
The rocks particles
were aligned
differently as you
moved out away
from the mid-ocean
ridge on either side
showing a pattern of
changes.
http://mail.colonial.net/~hkaiter/ContinentalDrift.html
Mid Ocean Ridge Formation
http://www.mysciencebox.org/files/images/seafloor_animation.gif
http://wgvu.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.wegen
er2/plate-tectonics-further-evidence/ WATCH THIS!
Evidence for a Changing Earth
PART 3
Chapter 1 Section 5
Plate Tectonics

http://wgvu.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.plateintro/
plate-tectonics-an-introduction/

http://wgvu.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.boundarie
s/tectonic-plates-and-plate-boundaries/ Look at the plates!
Lithospheric Plates of the Earth

The Earth’s lithosphere is broken into
plates that are constantly moving and
changing the surface of the Earth.
http://dreamtigers.wordpress.com/2011/05/11/plate-tectonic-metaphor-illustrations-cmu/
The Major Plates
List the names of the plates
2-D Earth 3-D Earth


Looking at the Earth from a 2-D map can
be misconceiving. Check out the site
below!
http://www.classzone.com/books/earth_science/terc/content/investigations/es0301/es0301page03.cfm
What is Plate Tectonics?
The term plate tectonics refers to how
the Earth's surface is made up of plates. In
geology, a plate is a large slab of rock,
while tectonics is a word of Greek origin
meaning "to build.“
 Plate Tectonics is the current theory that
explains how the surface of the Earth is
broken into plates that are slowly but
constantly forming, subducting and
changing to create the features of the
Earth’s surface.

Evidence for Plate Tectonics

The theories of continental drift and sea-floor spreading
gave a basis for the discovery of the plates. However
further evidence from the locations of earthquakes and
volcanoes helped to map their boundaries.
Evidence for Plate Tectonics
TIME LINE FOR THE
DEVELOPMENT OF THE THEORY
OF PLATE TECTONICS
http://www.britannica.com/EBchecked/top
ic/463912/plate-tectonics/301055/Timeline-of-the-development-of-the-theory-ofplate-tectonics
 Have to join to see this! UGH!

How do the Plates Move?

Geologists believe that convection
currents in the mantle provide the force
that moves the plates.

http://www.windows2universe.org/earth/interior/how_plates_move.html
How do the plates move?

http://www.youtube.com/watch?v=ctoMRrUwBwI New
evidence for movement of the plates. Time 1:15
Movement of the Plates
How do scientist know that the continents are moving
today?
http://www.pbs.org/wgbh/nova/ice/continents/
Have you ever rode bumper cars? The plates are moving
around like this crashing into each other, moving away
from each other, or sliding past each other. They all
move at different speeds, anywhere from a couple of
millimeters to several centimeters per year. Overall
they move very slowly. The place where the two plates
meet is called a plate boundary. There are three types
of boundaries. Faults occur along these boundaries
where the crust slips and fractures.
Diverging Plate Boundaries

Diverging boundaries occur where plates
are pulling apart.The mid-ocean ridge is the
most common divergent boundary. A rift
valley forms where these occur on land.
http://wdict.net/word/divergent+boundary/
The Great Rift Valley

The plates can
separate across a
continent too!
http://seeker401.files.wordpress.com/2011/01/image004.jpg
The Earth’s Surface Separates
http://science.discovery.com/tv-shows/when-earth-erupts/videos/african-rift.htm watch this series of 4
short videos about the rift valley.
http://www.sciencephoto.com/media/167053/enlarge
Converging Plate Boundaries
http://www.pbs.org/wgbh/nova/everest/earth/shock.html
Watch this to see how the Himalayan Mountains
are forming.
Converging boundaries can occur where two
continents are smashing into one another and form
mountains.

http://dreamtigers.wordpress.com/2011/05/11/plate-tectonic-metaphor-illustrations-cmu/
Converging Plate Boundaries

Converging plates also occur at
subduction zones where the ocean plates
dive below the continents forming deepocean trenches.
Transform Plate Boundaries

Transform boundaries happen where
plates are sliding past each other. One of
the most famous is in California, the San
Andreas fault, where the edge of
California is shearing off to the North.
http://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html
Hot Spots

Hot Spots are places where the Mantle
reaches up close to the surface of the crust
either near boundaries or in the center of
plates. The Hawaiian Islands are formed this way,
as well as places like Yellowstone National Park.

http://www.geology.sdsu.edu/how_volcanoes_work/intraplvolc_page.html
What are hot spots?
Hot Spots around the Earth
The Search for New Evidence
Continues!

Trip to the bottom of the Mariana Trench,
the deepest place in our oceans.

http://en.wikipedia.org/wiki/Mariana_Trench
Information here.

http://www.youtube.com/watch?v=Y2tm40uMhDI
Time 2:05 Released March 2012 National Geographic
 http://www.youtube.com/watch?v=RxUZMcLtGg&feature=player_embedded Video from Oct.
2011 showing jellyfish at bottom of trench and
Xenophyophores,giant single-celled sea creatures that
can be 4 inches wide.
Life at the bottom of a
Mid-ocean Ridge
http://wgvu.pbslearningmedia.org/resource/tdc0
2.sci.ess.earthsys.deepseavents/deep-sea-ventsand-lifes-origins/ “Deep Sea Vents and Life’s
Origins”Time 4 min.
 http://wgvu.pbslearningmedia.org/resource/nsn0
9.sci.life.eco.seafloor/exploring-the-arcticseafloor/ Exploring the Arctic sea floor.
 http://wgvu.pbslearningmedia.org/resource/ipy0
9.sci.life.eco.scini/studying-the-antarctic-seafloor/ Exploring the Antarctic sea floor using a
ROV called SCINI.
