Download Earth`s Tectonic Plates - kmstorres

Name
Earth's Tectonic Plates
by Cindy Grigg
Answer the following questions BEFORE you read this book. It is
okay if you do not know as much as you thought. Do the best you
can!
:KDWGR\RXDOUHDG\NQRZDERXWSODWH
WHFWRQLFV"
&RXOGDOORI(DUWK
VODQGKDYHEHHQMRLQHG
WRJHWKHUDWRQHWLPH"+RZGR\RXNQRZ"
Our Earth looks solid and unchanging. But
looks can be deceiving!
The solid, outer layer of the Earth is made of
rock. It is called the lithosphere. The
lithosphere consists of the crust and the solid
part of the upper mantle. However, the
lithosphere is not a solid piece. Instead, it is
made of huge slabs of rock that fit together
like a jigsaw puzzle. The pieces are called
tectonic plates. There are about eight large
plates and several smaller ones, too. Earth's
land and oceans sit upon these plates. As
you can see, the plates are not the same as
the continents.
:KDWFDXVHVHDUWKTXDNHVDQGYROFDQRHV"
:KDWPDNHVWKHPKDSSHQLQFHUWDLQ
SODFHV"
1
2
Earth's Tectonic Plates
Under the lithosphere is the asthenosphere.
This part of the Earth's upper mantle is
warmer than the lithosphere. Because of the
heat, the asthenosphere is less rigid and able
to flow. If you've seen the movie Charlie and
the Chocolate Factory, you might think of
the asthenosphere like Charlie's chocolate
river.
When plates move, three things can happen.
First, they can pull away from each other in
opposite directions. This is happening in
eastern Africa. Three plates are slowly
pulling apart in the East African Rift Zone.
The boundary between two plates pulling
away from each other is called a divergent
boundary.
The tectonic plates of the lithosphere stay
together. But they move about on the fluid,
moving asthenosphere, like boats floating on
a very thick, gooey chocolate river. As they
move, the plates bump against each other
like bumper boats!
3
4
Earth's Tectonic Plates
In the North Atlantic Ocean, the Eurasian
Plate and the North American Plate are
pulling away from each other. In the South
Atlantic Ocean, the South American Plate
and the African Plate are also pulling apart.
The Mid-Atlantic Ridge has formed at these
divergent boundaries. It is the longest
mountain range in the world-and it's under
water!
What do you think happens between the two
plates as they diverge (move away from each
other)? The hot, molten rock inside the Earth
oozes out. New lithospheric crust is formed.
5
6
Earth's Tectonic Plates
The island of Iceland is on the Mid-Atlantic
Ridge. It formed when molten rock pushed
its way to the top of the ocean's surface.
Because of its location, Iceland has many
active volcanoes, hot springs, and geysers.
Iceland uses this heat from inside the Earth
to provide electricity and hot water for its
320,000 residents.
Tectonic plates can move toward each other
and smash together. When two plates push
toward each other, their boundary is called a
convergent boundary.
7
8
Earth's Tectonic Plates
A third way plates move is to slide past each other.
Their boundary is called a transform boundary.
This is happening in California along the San
Andreas Fault.
In Asia, two plates are converging. They are
pushing against each other like two bulls
butting their heads together. The pressure is
pushing rock upward. The Himalaya
Mountains are being built from these
converging plates. These tallest mountains
on Earth began to form millions of years ago
when the Indian plate collided with the
Eurasian plate. The Eurasian plate is
winning this pushing contest. The Indian
plate is being subducted, or pulled under.
The Eurasian plate is being lifted up. The
Himalayas are growing taller all the time.
The Pacific plate is sliding northwest. The North
American plate is sliding southeast. As they slowly
grind past each other, sometimes they get stuck.
Pressure builds up. It is released when there are
earthquakes.
Photo credit: NASA
9
10
Earth's Tectonic Plates
Wegener noticed that South America and
Africa looked as though they could fit
together. He found that rocks in both places
were of the same type and age. Fossils of the
same plants and animals were found in both
places. He proposed the idea of continental
drift - that the continents had once been
joined but had moved apart. This idea existed
even before Wegener found evidence of it.
However, it was not accepted by scientists
because no one was able to explain what
force could move something as big as
continents.
We usually can't feel the Earth's plates
moving. That's because the movement
happens very slowly. The theory of plate
tectonics explains why and how the Earth's
plates move.
The idea that the continents drifted or moved
began in the early 1900s with Alfred
Wegener.
11
12
Earth's Tectonic Plates
Suppose you are living in 1912. You want to
help Wegener explain how something as big
as continents can move. Draw a picture that
shows your explanation.
Wegener didn't know that heat inside the
Earth cause the continents to move around.
The mantle is made of thick, dense material.
The plates are lighter and float on top, like
oil floats on water's surface. Heat in the
deepest part of Earth's mantle causes pockets
of the material to heat, expand, and move
upward.
You can see these movements, called
convection currents, when water boils in a
pan on the stove.
After the pockets of heated material rise,
they cool and sink. This cycle of heating and
rising, cooling and sinking, repeats over and
over. The plates floating on top are moved by
these convection currents.
13
14
Earth's Tectonic Plates
In the 1960s, geologist Harry Hess suggested
that the sea floor was moving outward from
the mid-ocean ridges. He stated that new
lithospheric crust forms at a mid-ocean ridge.
Then it is slowly pushed away on both sides
toward the continents as more new crust is
produced. This, along with other evidence
from sea floor mapping in the 1950s and
1960s, supported Wegener's idea and the
theory of plate tectonics.
Scientists have plotted the locations of
earthquakes and volcanoes on a map. They
found that the Pacific Ring of Fire is home to
about 90% of the world's earthquakes and
75% of the world's volcanoes. The Pacific
Ring of Fire is a direct result of tectonic plate
movements.
This diagram shows the age of oceanic crust.
The youngest crust, shown in red, is along
diverging boundaries.
15
16
Earth's Tectonic Plates
Answer the following questions AFTER you have completed this
book.
7KHVROLGRXWHUOD\HURIWKH(DUWKLV
FDOOHGWKH
&LUFOHWKHFRUUHFWDQVZHU7KH5LQJRI
)LUHLVVKDSHG
The Earth's surface is made up of a dozen or more
pieces called tectonic plates. Our planet's internal
heat causes the plates to move slowly about. As
they slide, collide, and subduct, they affect life on
Earth. Volcanoes erupt. Earthquakes shake.
Mountains and islands are created. It's all part of
our dynamic and mobile Earth.
17
OLNHDFLUFOH
OLNHDKRUVHVKRH
OLNHDKRQH\FRPE
OLNHDVSKHUH
:KHUHLVWKH5LQJRI)LUH"
18
Earth's Tectonic Plates
&LUFOHWKHHIIHFWVRISODWHWHFWRQLF
PRYHPHQWV
:KDWHYLGHQFHGLG:HJHQHUKDYHWKDW
6RXWK$PHULFDDQG$IULFDZHUHRQFH
MRLQHG"&LUFOHDOOWKDWDSSO\
PRXQWDLQEXLOGLQJ
PXGVOLGHV
6RXWK$PHULFDDQG$IULFDORRNHGOLNHWKH\
FRXOGILWWRJHWKHU
FUHDWLRQRIFRUDOUHHIV
7KHLVODQGRI,FHODQGIRUPHGGXULQJKLVOLIHWLPH
FUHDWLRQRIQHZLVODQGV
5RFNVLQERWKSODFHVZHUHRIWKHVDPHNLQGV
HDUWKTXDNHV
9ROFDQRHVHUXSWLQWKH5LQJRI)LUH
WURSLFDOVWRUPV
5RFNVLQERWKSODFHVZHUHRIWKHVDPHDJH
YROFDQLFHUXSWLRQV
5RFNVLQERWKSODFHVFDPHIURPWKHVDPH
YROFDQR
:KDWFDXVHV(DUWK
VWHFWRQLFSODWHVWR
PRYHDURXQG"
7KHVDPHNLQGVRIIRVVLOVZHUHIRXQGLQERWK
SODFHV
7KHVDPHNLQGVRIDQLPDOVZHUHFXUUHQWO\
OLYLQJLQERWKSODFHV
([SODLQWKHGLIIHUHQFHEHWZHHQ
FRQYHUJHQWGLYHUJHQWDQGWUDQVIRUP
ERXQGDULHV
Earth's Tectonic Plates
19
20
Earth's Tectonic Plates
,PDJLQHWKDW\RXDUH$OIUHG:HJHQHU
<RXKDYHHYLGHQFHWKDW$IULFDDQG6RXWK
$PHULFDZHUHRQFHMRLQHGEXW\RXFDQ
W
JHWDQ\RQHWREHOLHYH\RX<RXKDYH
LQIRUPDWLRQWKDW:HJHQHUGLGQ
WKDYHLQ
8VHZKDW\RXNQRZQRZDQGZULWH
DVSHHFKWKDWZLOOFRQYLQFHVFLHQWLVWVWKDW
\RX:HJHQHUDUHFRUUHFW
Earth's Tectonic Plates
21
22
Earth's Tectonic Plates