Download Plate Tectonics and Layers of the Earth

Plate Tectonics and Layers
of the Earth
Ch. 10 - p. 270 – Earth
Standards:
S6C1:PO2, PO3, PO4
S6C2: PO3, PO4, PO5
Plate Tectonics Launch Lab!
• You will be working with the person sitting next to you.
• I will pass out a picture to you and your partner. Make
sure no one other than the two of you sees which picture
you received.
• You need to cut the picture up into 10-15 pieces. Make
sure that each piece has a shaped edge…you cannot
just cut it into squares.
• Once you have cut your picture into pieces, trade with
the other group at your table.
• Complete the puzzle using different strategies.
• Be ready to explain which strategies you used to solve
the puzzle.
What I think I know
About plate
Tectonics,
Earthquakes and
Volcanoes:
Facts (what I definitely know)
about plate tectonics,
Earthquakes and volcanoes:
New information
About plate
tectonics,
Earthquakes and
volcanoes:
Background Information: Layers of the Earth
•
•
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The Earth is made up of several layers that have
different properties and compositions.
There are three main layers:
–
Crust
–
Mantle
–
Core (inner and outer)
The lighter materials are the outermost layer, and the
heavier materials are the inner, deeper layers.
1) Crust:
- Outermost layer
- Floats on top of the mantle
- Less than 1% of the Earth’s mass
- Ranges from 5 to 60 km thick – thinnest
layer
- We know most about this layer. Why?
Two types of crust on Earth:
Continental Crust
- Similar to granite
- Between 20 – 60 km thick
Oceanic Crust
- Similar to basalt – more dense
than
granite
- Between 5 – 8 km thick
Both types of crust contain many tectonic
plates that float on top of mantle
•
2) Mantle:
– Layer between the crust and the core
– About 67% of the Earth’s mass
– 2,885 km thick
– No one has seen mantle layer – too deep to drill to get sample
– Some places on Earth, mantle rock has been pushed through
surface
• Molten rock from mantle layer flow from volcanoes on ocean
floor
– Made up of mostly iron (Fe) and magnesium (Mg)
•
Mantle contains 2 main layers:
– Upper Mantle
• Base of crust to depth of 660 km
– Lower Mantle
•
•
• Depth of 660 km to 2225 km
Crust and top of Upper Mantle together are called the Lithosphere
• About 100 km thick
• Contains area of earthquakes, mountain building, volcanoes
and continental drift
Just below Lithosphere is area called Asthenosphere
– About 100 – 200 km thick
3) Core:
- About 33% of Earth’s
mass
- 6,972 km in diameter
- Made up of mostly iron
(Fe) and nickel (Ni)
- Contains 2 layers:
- Inner Core – center of
Earth
- Solid
- Outer Core
- Liquid
- Surrounds Inner
Core
The planet Mars is actually
smaller than the core of Earth
(Mars = 6,787 km)
• Continental Drift
: hypothesis that states that the
continents have moved
slowly to their current
locations on Earth
•
•
•
•
•
In 1912, Arthur Wegener
suggested that all the
continents were connected
as one land mass
Large land mass of all the
connected continents was
called:
• Pangaea = “ all
land”
Suggested Pangaea broke
apart about 200 million
years ago
Hypothesis wasn’t accepted
until after Wegener died in
1930
Puzzlelike fit of continents
was Wegener’s first
evidence for Continental
Drift
Fossil Evidence of Continental Drift:
- Fossils from the reptile Mesosaurus were found
in South America and Africa
- Unlikely to swim between continents
- Wegener thought reptile covered both
continents during Pangaea period
- Fossils from fernlike plant Glossopteris
- Found in Africa, Australia, South
America and Antarctica
-Wegener thought this showed continents had to
be connected at one point in time = Pangaea
Climate Evidence of Continental Drift:
- Fossils of warm weather plants were found on
island in Arctic Ocean
- Wegener thought island drifted from tropic
regions
- Glacial deposits and grooved bedrock on
South America, Africa, India, and
Australia
- Shows they were once covered with
glaciers
- No glaciers exist in those areas today
Wegener thought they were all connected near the
Earth’s south pole at one time
• Rock Evidence of Continental Drift:
– If continents were connected as Pangaea, shouldn’t
rocks be similar on different continents?… YES!
– Similar rock structures and types of rocks are found
on different continents
– Appalachian Mountains (below left) in eastern United
States are similar to mountains in Greenland and
Western Europe (below right)
– South America and western Africa have similar rock
structures
- Wegener had some good evidence for Continental Drift…
But… the big questions of how, exactly when or why this
happened still weren’t answered.
- Most people rejected his idea of Continental Drift
- After Wegener’s death, more clues were found to support
Continental Drift.
- New idea… SeaFloor Spreading, helped explain how the
continents could move.
- Proposed by Harry Hess in 1960’s
- SeaFloor Spreading
: as hot, less dense material is forced up through the Earth’s
crust in an opening called a mid-ocean ridge, it turns and flows
sideways, carrying the seafloor away from the ridge in both
directions
This would cause continents to move away from each other
• Evidence for SeaFloor Spreading:
• Movement of sea floor
– Process of seafloor spreading…
• Age evidence:
– 1968 – research ship – Glomar Challenger – gathered samples
of sea floor rocks
– Checked age of rocks
– Rocks on sea floor – near mid-ocean ridge – were 180 million
years old or younger
– Rocks away from mid-ocean ridge – near continents – some
were almost 4 billion years old
– WHY?
Magnetic Clues:
- Magnetic field of Earth has a North and South pole
- Magnetic force leave at the south pole and enter at the north pole
- During a magnetic reversal – the magnetic forces run in opposite
way
- Reversal has happened many times in past
- Iron bearing minerals – magnetite, which is in basalt, record Earth’s
magnetic field direction
- Rocks show the effects of the reversal – new iron minerals are
formed
- Magnetometer records magnetic data
- Magnetic alignment in the rocks reverses back and forth over time –
these match and are parallel with mid-ocean ridges
Why is this Important? – it shows new rock was being formed at the midocean ridges
Plate Tectonics:
(pg. 280)
•
•
•
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Seafloor spreading let
scientists know what was
happening with the crust
and upper mantle
It also showed that there
was more than just
continents moving…
– Larger sections were
moving
1960 – scientists
developed a new theory
that put continental drift
together with seafloor
spreading
Theory of Plate Tectonics:
Earth’s crust and upper
mantle are broken into
sections… theses
sections – called plates,
move around on a layer of
the mantle
Which layer are the plates
a part of?
What causes Plate Tectonics?
- Process of heating and
cooling, which causes movement
of particles is called convection
current
- Hot particles rise, cool
particles lower…
- Continuous process keeps
particles moving…
creates
energy
- These convection currents
provide energy that
moves
plates
Effects of Plate Tectonics:
Plates are constantly interacting
with other plates…
What does this do to the Earth?
- Forms mountain ranges,
volcanoes, faults, rift
valleys
Three types of plate boundaries: (pg. 281)
1) Boundary between plates that are moving apart = divergent
boundary
2) Boundary between plates that are moving together = convergent
boundary.
- Area where one plate goes down into the mantle is called the
subduction zone.
- Volcanoes usually form near convergent boundaries when the
rock melts or mountains can form when two plates collide and
crumple up.
3) Boundary where plates are sliding past each other = transform
boundary