Transcript Plate Tectonics

Plate Tectonics
•Earth’s Layers
•Continental Drift
•Seafloor Spreading
•Plate Tectonics Theory
Earth’s History
How old is our Universe?
13.7 billion years old
How old is Earth?
4.6 billion years old
Earth was once made of molten
lava and magma, eventually
cooling to igneous rock
Weathering,
Erosion,
Compaction,
Cementation,
Heat, and
Pressure
eventually formed
the rocks that
cover our Earth’s
surface.
What we know about Earth’s history
comes from studying its rocks and rock
formation and even the rocks from outer
space
Meteorites
• All meteorites formed
about the same time
that Earth formed, so
studying them helps
us study Earth.
• Meteorites have not
been affected by
erosion, weathering
or other forces the
way Earth’s rocks
have.
Studying Earth’s Rocks
Rock Layers
• Which book was
placed here first?
• The bottom one!
• Sedimentary rocks
often follow a similar
pattern, oldest rocks
are found on the
bottom.
http://www.prehistoricplanet.com/news/index.php?id=48
• Digging through
the layers of
rocks, helps us
understand
more about the
history of Earth.
Fossils
• Most fossils are found in
Sedimentary rock layers
• Why?
– Heat, pressure, and
melting would
probably destroy
fossils during the
formation of Igneous
and Metamorphic
rocks
• The Grand
Canyon (AZ) was
carved by the
Colorado river,
exposing millions
of years worth of
rock layers.
Sometimes, the rock layers aren’t
always horizontal…
And sometimes ocean fossils are
found high in the mountains…
Why?
• Turns out, our
Earth’s surface
is constantly
shifting and
changing.
• Sometimes
layers get
pushed around.
• Only in the last
200 years, have
we begun to
understand the
structure and
formation of our
Earth.
I wonder
what’s inside
Earth?
Homework: Draw a picture of an
apple/egg/avocado cut in half and explain
why this is similar to the layers of Earth’s
interior.
Page
135
“fruit” = mantle
Seeds =
inner
core
Skin = crust
Seed coat =
outer core
shell =
crust
white =
mantle
Outer
yolk =
outer
core
Center
yolk =
inner
core
“fruit”
=
mantle
Seed center
=
inner core
skin =
crust
Seed shell
=
outer core
Earth’s Layers
Earth’s Layers
Crust
(10-25 miles)
1,800 miles
1,430 miles
750 mile
radius
Inside Our Earth
Mantle
Outer Core
Inner Core
The crust is made of soil,
water and rock.
The mantle is hot. Part
melted and part solid
iron and magnesium.
The outer core is
made of hot liquid
nickel and iron.
The inner core
is made of solid
nickel and iron.
Composition of the Earth’s Layers
• The Lithosphere is made of the crust
and upper mantle
• The Lithosphere is broken into many
sections or plates.
• Some plates are lighter than others.
•The lithosphere is made of two igneous rock types:
•Continental crust - granite (light)
•Oceanic crust - basalt (heavy)
•Because granite is lighter than basalt, the
continents sit on top of the denser oceanic plates
•Mantle is the largest layer over 1800 miles
thick
•It is composed of mostly liquid rock that
moves due to temperature differences
•1800 degrees F at the top, 4000 degrees F
near the bottom.
•Outer Core-Very hot liquid metals 4,000
degrees F to 9000 degrees F
•Made of Nickel and Iron
•This liquid core produces a magnetic field
that helps protect earth from coronal mass
ejections (CME’s) produced by the sun.
Protective Magnetic Field
•In the Inner Core, temperatures and pressures are
so great, the liquid metals are forced back into a
solid despite the high temperatures that would
normally melt them.
•45,000,000 pounds of pressure per square inch.
•3,000,000 times more pressure than felt at sea
level.
How do we know what’s
inside?
• Geologists study earthquakes and
volcanoes
Seismic waves
caused by
earthquakes change
direction as they
move through
different materials
(such as solids and liquids)
http://www.classzone.com/books/earth_science/terc/content/investigations/es0402/es0402page03.cfm
Earthquake wave animation:
http://neic.usgs.gov/neis/eq_depot/2002/eq_021103/ak_seismic_waves.html
I’m going to dig a hole to _____
Dig a hole to the other side of
Earth
http://www.ubasics.com/dighole/
http://www.livephysics.com/ptools/dig-hole-throughearth.php
I’m going to dig a hole to China!
• You will have to start in Chile, South
America
Will you make it to the other
side?
• If you could survive the temperatures
(over 8,000 degrees F) and the
pressure (3,000,000 times the force of
gravity) and you could “climb” out the
other side (down is towards the center
of Earth), then YES!
• If you could just freefall all the way
through Earth (8,000 miles) it would
take you about 67 hours falling at 120
mph.
http://www.daviddarling.info/childrens_encyclopedia/Dig_a_Hole_to_China_Chapter5.html