Download Lithospheric Plates

LITHOSPHERIC PLATES
EQ: How do the
lithospheric plates
movement affect Earth’s
surface?
Lesson 19
Lithospheric Plates
• What features of Earth are
produced by the
movement (colliding and
sliding) of lithospheric
plates?
• What was Alfred
Wegener’s hypothesis?
• What is a scientific
hypothesis?
• What does the collision of
two continental plates
produce? (example)
Cornell Notes – Lithospheric Plates
• What does the collision of a
continental plate and a oceanic
plate produce? (example)
• What does the collision of two
oceanic plates produce?
(example)
• What is produced when two
plates slide by each other?
(example)
How has the Earth changed in the last
250 million years?
Lithospheric Plates
• Earth's surface is like a jigsaw puzzle in motion
• The pieces in the puzzle are made of large chunks of
Earth’s lithosphere
• Lithosphere is the solid outer layer of Earth
• It includes the crust and the top of the mantle
• The moving chunks of the lithosphere are called
lithospheric plates
• Continents and the ocean floor rest on these plates
• Where these plates collide or separate, events take
place that shape Earth’s surface
What is the Lithosphere?
• Lithosphere- The solid, outer layer of the Earth
that consists of the crust and the rigid upper part
of the mantle.
• Divided into pieces
called tectonic plates.
The Major Plates of Our Lithosphere
What was Alfred Wegener’s hypothesis?
Continental Drift
Continents in Motion
• German scientist, Alfred Wegener (VAY guh nuhr ), hypothesized
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•
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that all land masses on Earth had once made up a single, giant
continent.
A hypothesis is a proposed explanation for one or more
observations.
As millions of years passed, pieces of this giant continent
separated and moved to their present positions
This process is called continental drift
Continents move about 2 cm a year
Continents in Motion
• After years of observations
Wegener came up with a
hypothesis he called
continental drift.
• He thought all the
continents were once
joined in a single, huge
continent.
• CONTINENTAL DRIFT-
The hypothesis that states
that the continents once
formed a single landmass,
broke up, and drifted to
their present locations.
Evidence Number 1: Fossils
• Fossils can show evidence of continental drift
• For example, Mesosaurus was a reptile that lived
more than 250 million years ago
• It lived in freshwater lakes and rivers
• Scientists found its fossils in both South America
and Africa
• These continents are now separated by the salty
Atlantic Ocean
• How did their remains end up on both continents?
Fossil Evidence
More Fossil Evidence
• Mesosaurus & Lystrosaurus- found
in places now separated by oceans
• Glossopteris- fernlike plant found in
rocks in Africa, S. America,
Australia, India & Antarctica
More Fossil Evidence
Evidence Number 2: Landforms
• Continents
puzzle-like fit
• Mountain
ranges of Africa
and South
America line up
Coal Deposits
European
coal fields
match up with
similar coal
fields in North
America
Evidence Number 3: Climate
• Island of Spitsbergen
• Lies in Arctic Ocean; harsh, polar
climate
• Fossils of tropical plants found here
• Glaciers
• Evidence of past continental glaciers
found in rocks of South Africa
What are the three types of Boundaries?
Events Caused by Moving Plates
• Scientists divide Earth’s lithospheric plates
into two groups• Less dense continental plates
• More dense oceanic plates
The movement of these plates produce
different events on Earth’s surface
Continental Plate vs. Continental Plate
• When two continental plates collide, neither
slides under the other
• The plates buckle upward where they meet
• This buckling produces mountain ranges
• Example: the Himalayas in Asia
Continental collides with Continental
Oceanic Plate vs. Oceanic Plate
• When two oceanic plates meet, one slides under the other
• This action is called subduction. The area in which this
takes place is called a subduction zone.
• A deep trench in the ocean floor forms and volcanic islands
may pop through the ocean’s surface.
• The Aleutian islands between Alaska and Russia were
formed this way
Oceanic Plate vs. Continental Plate
• When an oceanic plate runs into a continental plate, the more
dense plate slides under the less dense plate (subduction)
• This causes volcanic mountains like Mount St. Helens in the
state of Washington to form.
Earthquakes!
• Some plates get stuck as they push into each other or slide
past each other.
• When they become unstuck, a sudden jolt happens.
• Energy is released and energy sends waves through the
ground. (seismic waves)
• This causes the ground to shake…It’s an earthquake!
Earthquakes Part 2
• Earthquakes occur more frequently along plate boundaries
than anywhere else.
• This accounts for the “Ring of Fire” that curves around the
Pacific Ocean.
• The “Ring of Fire” is a belt where volcanoes and earthquakes
are very common.
• The belt follows the borders of plate boundaries.
Ring of Fire
Quick Check
1. What features of Earth are produced by the movement of
lithosphere plates?
A. solid masses of iron and nickel
B. liquid masses of iron and nickel
C. red-hot magma
D. mountains ranges, volcanoes, and volcanic islands
Quick Check
2. What was Alfred Wegener’s hypothesis?
A. The continents have always been where they are now.
B. Today’s continents were once part of a single land mass that split
apart.
C. The continents are made of rock.
D. The continents will one day join to form a single continent.
Quick Check
3. Earthquakes are MOST LIKELY to occur at the borders
of
A. continents.
B. lithospheric plates.
C. countries.
D. oceans
Quick Check
4. A scientific hypothesis is
A. a fact.
B. an explanation that has been supported by repeated observations
and experiments.
C. a proposed explanation for one or more observations.
D. a guess that is not based on observations.
Quick Check
5. The collision of two continental plates can produce
A. volcanic islands.
B. a mountain range.
C. a single mountain
D. a trench.
Quick Check
6. When two plates converge, one plate is usually forced to
slide under the other. Oceanic plates are more dense than
continental plates. If an oceanic plate collides with a
continental plate, what will be the likely result?
A. The continental plate will slide under the oceanic plate,
generating an oceanic trench.
B. The oceanic plate will slide under the continental plate,
generating an oceanic trench.
C. The continental plate will slide under the oceanic plate,
generating an earthquake.
D. The oceanic plate will slide under the continental plate,
generating an earthquake.
Quick Check
7. If two plates meet at a convergent boundary and do not
form a subduction zone, they may
A. fold.
B. fault.
C. weather.
D. erupt.
Quick Check
8. The process of seafloor spreading occurs at what kind of
plate boundary?
A. divergent
B. convergent
C. transform
D. at both convergent and transform boundaries
Quick Check
9. Where does magma come from?
A. the inner core
B. the outer core
C. the mantle
D. the lithosphere
Quick Check
10. The ancient supercontinent, Pangea, once
contained
A. all of the Earth’s tectonic plates.
B. all of Earth’s crust.
C. all of Earth’s continental crust.
D. all of Earth’s oceanic crust