Download Earth*s Structure

Unit D Chapter 1 Lesson 1
Pages D6-D11
Our planet is about
4.54 billion years old
(give or take a few
million)
 It started out as a huge
collection of molten
rock which formed our
planet.
 As the outer layer
started to cool (it took
about 400million years)
it formed our crust.
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Artist conception of early
Earth….not quite ready for life.
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You would have to travel
about 4000 miles to
reach the center of the
planet.
Unfortunately, you would
be completely destroyed
by doing this.
Temperatures near the
center are over 10,000
degrees F.
The pressure is also so
extreme it would smash
you into people paste.
Hollywood lies to us once again!!!
Curse you Brendan Fraser!! Next
thing you know, we’ll find out
mummies don’t come back from the
dead either.
How do we know
information on the
inner layers if we can’t
go there?
 Scientists can drill
down for the first 6
miles or so in the crust.
 They must base their
hypotheses on the
patterns and speed of
earthquake waves and
how they travel.
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Earth is made of three
main layers. The crust,
mantle, and core.
The mantle and crust
have two small layers
inside them called the
lithosphere and
asthenosphere.
The core is divided into
the outer and inner core.
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This is what not to do when
cracks in the crust open up.
The crust is about 20
miles thick under the
continents, and about 5
miles thick under the
ocean.
The continental crust is
made of granite, oceanic
crust is basalt, a much
He learned that lesson after stepping in this.
denser rock.
Scientists are currently
working on a $1billion
project to drill through
the oceanic crust.
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The lithosphere includes
all of the crust and part of
the upper mantle.
It contains earth’s
tectonic plates.
It is divided into seven
major tectonic plates.
The lithosphere actually
floats on top of the
asthenosphere.
This scuba diver is between two of the
tectonic plates. He has one hand on
North America, and one on Europe.
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The asthenosphere is a
zone of partially melted
rock in the upper mantle.
It has a property called
plasticity, which means
that it can flow.
The asthenosphere flows
because heat from
deeper in the earth
causes currents.
Silly putty behaves in a
similar (and safer)
manner.
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The mantle is our
thickest layer, about 1800
miles thick.
The upper mantle is
about 2900 degrees and
about 7200 degrees near
the core.
This is hot enough to
melt rock, but only the
upper mantle is partially
melted.
The rest is solid because
of tremendous pressure.
Molten rock called magma can be
pushed up from the mantle, escaping
through cracks in the crust.
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The outer core is an
extremely hot layer of
liquid metals, mostly iron
and nickel. Temps range
from 8-11 thousand
degrees.
The inner core is mostly
iron and solid, with
temperatures from 9-13
thousand degrees.
The metals should melt at
this temp, but the pressure
is so great it forces it into a
solid state.
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Plate Tectonics is the theory scientists use to explain plate movement.
Teconics comes from the Greek word meaning “builder.”
The seven major plates are named for the continents or oceans they carry.
The largest plate is the “Pacific Plate.” It covers 1/5 of Earth’s surface.
A map of the plates can be found on page D8-D9 of your book.
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The plates of the
lithosphere constantly
change in shape and size.
They may split or combine
with other plates.
They can be pushed back
into the earth and be
melted down again.
The crust under the ocean
is newer, thinner crust.
Continental crust is older
and thicker.
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Plate movement causes
earth’s surface to change
constantly.
They form mountains, and
trenches.
The boundaries where
plates meet are the sites of
earthquakes and
volcanoes.
Other forces can slowly
change the surface of earth.
Erosion and glaciers carve
away at the crust.
Earth’s surface is
changed rapidly when
hit by objects from
space.
 Meteoroids are rocks
floating in space, when
they enter our
atmosphere, they heat
up and burn.
 They are seen as
“shooting stars” but
are now called
meteors.
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 Meteors
that actually
hit the earth are
called meteorites.
 More than 19,000 fall
to earth each year but
are so small no one
notices.
 A few though, can
make a lasting
impact.