8.9(A) Describe the historical development of
evidence that supports plate tectonic theory.
Evidence for plate tectonics
The match in shape between the east coast of
South America and the west coast of Africa
suggests both were once part of a single
continent. There are similar patterns of rocks and
similar fossils on both sides of the Atlantic including the fossil remains of land animals that
would have been unable to swim across an ocean.
Mantle
Outer core
Inner core
Crust
The plates
are moving
at a speed
of 1 to 10
cm per
year.
The crust is not a solid shell;
it is broken up into huge, thick plates.
The Movement of
the Earth's Plates
The cause of
earthquakes, volcanoes, mountain range
formation, and many other crustal features.
Solve the puzzle to discover what the Earth looked like
220 million years ago.
1. What’s the Code? Use the legend to identify the symbols
on each island or continent.
2. Puzzle me this. Look at the shapes of continents and
islands. What landmasses seem to fit together?
3. Let’s rock! Examine the evidence and try to match up
landmass boundaries that show similar rock strata,
fossilized desert belts, and dinosaur fossils.
4. Hold that pose. Look over the arrangement of the
continents and islands and decide if the position of any of
them should change. When you are satisfied with your
map of Pangaea, tape or glue it down on he world map.
Answer these questions:
1. Rock type, fossils, glacial deposits, and glacier "tracks", are
four types of ........ that support the theory of plate tectonics.
2. Explain why similar fossils can be found on opposite sides
of an ocean, when there is no way the organisms could have
traveled that far when alive.
3. Explain why fossils of tropical animals are found in
Antarctica even though the poles of the Earth have never
been warm.
Wegener hypothesized that there was a
gigantic supercontinent 200 million years
ago, consisting of all of Earth’s land
masses, which he
named Pangaea,
meaning
"All-earth".
In 1915, the German geologist and
meteorologist Alfred Wegener first
proposed the theory of continental
drift,
which
states
that parts of the
Earth's crust slowly
drift atop a liquid
core.
1. Puzzle-fit of Land
Masses
225
200million
millionyears
yearsago
ago
135
million
years
ago
65 million years ago
Present Day
2. Fossil Evidence
Alfred Wegener traveled the world, and noticed...
Fossils of
Mesosaurus
(one of the first
marine reptiles,
even older than
the dinosaurs)
were found in both
South America and
South Africa.
...matching rocks and fossils on distant coastlines.
3. Convection currents beneath the plates move
the crustal plates in different directions.
A convection current flows
from hottest to coolest in
the mantle.
EARTH'S HISTORY
For
Understanding
A) Using the diagram, identify two pieces of
evidence that support the scientist's theory that
the land masses were once together.
ANSWER: (puzzle-fit of land masses, matching
rock and fossil territories on distant shorelines)
8.9(B) Relate plate tectonics to the formation
of crustal features.
Plate tectonics explained why earthquakes
and volcanoes were concentrated in
specific places - around the boundaries
of moving plates.
Name__________________________
Date_________________Period_____
Plate Tectonics
Divergent Plate Movement:
Seafloor spreading is the
movement of two _________
plates away from
each other.
The top layer of the Earth's surface
is called the ________.
_________ is constantly being created and destroyed.
Results in the formation of
new oceanic _________along
a mid-ocean ridge.
__________
crust is more
active than
__________
crust.
Convergent Plate Movement:
When two plates collide
When an oceanic plate
collides with a continental plate,
the oceanic plate is forced under
the continental plate; this is called
_______________.
When two oceanic plates collide, one may be pushed under
the other and magma from the mantle rises, forming
___________.
When two continental plates collide, ____________
_________ are created.
Transform Plate Movement:
When two plates move sideways
against each other,
an __________________
is produced.
Most of the Earth's seismic activity (volcanoes and
earthquakes) occurs at the plate boundaries as they interact.
The top layer of the Earth's surface
is called the crust.
Crust is constantly being
created and destroyed.
Type
of
Crust
Average
Thickness
Average Age
Major
Component
10 kilometers
20-80 kilometers
(Thin and Dense)
70-100 million years old 3 billion years old
Basalt
Granite
Oceanic crust is more active than continental crust.
Most of the Earth's seismic activity (volcanoes
and earthquakes) occurs at the plate boundaries
as they interact.
Divergent Plate Movement:
Seafloor spreading is the
movement of two oceanic
plates away from each other.
Results in the formation
of new oceanic crust (from
magma that comes from
within the Earth’s
mantle) along a
mid-ocean ridge.
Divergent Plate Movement: Seafloor Spreading
Ocean Ridge
Ocean
Oceanic Crust
Mantle
Magma
Asthenosphere
Convergent Plate Movement:
When two plates collide
When two oceanic
plates collide, one may
be pushed under the
other and magma from
the mantle rises,
forming volcanoes.
Convergent Plate
Movement:
When two plates collide
Convergent Plate Movement: Subduction
Subduction Zone
Ocean
Volcanos
Continental
Crust
Oceanic Crust
Mantle
Magma
Aesthenosphere
Transform Plate
Movement:
When two plates
move sideways
against each other,
an earthquake is
produced.
2. Which type of plate is thicker?
3. What is it called when two
oceanic plates move apart
and new crust is formed?
Wegener
Mountain
Range
5. What can form when two continental plates collide?
6. What do plates float on?
Subduction
Seafloor Spreading