Transcript Notes: Plate Tectonics

What is the structure
of Earth?
Notes: The Earth System
pg. 69
• A system is a group of parts that work together as
a whole.
• The constant flow, or cycling, of matter through
the Earth system is driven by energy.
• Energy is the ability to do work.
• Energy that drives the Earth system has two main
sources:
1.) heat from the sun
2.) heat flowing out of Earth as it cools
Earth’s System Has 4 Main
Spheres:
pg. 69
1.) Atmosphere- Earth’s outermost layer made
up of
a mixture of gases: mostly nitrogen and
oxygen. Contains dust, cloud droplets, water
vapor, rain, snow, earth’s weather
2.) Geosphere- the solid rocks and metals
that make up the Earth. Four parts: crust,
mantle, outer core, inner core
pg. 69
pg. 69
3.) Hydrosphere- Contains all of Earth’s water.
Water covers about ¾ of Earth’s surface.

97% is salt water

2% is frozen in the polar ice caps

1% is drinkable (fresh water)
pg. 69
4.) Biosphere- the parts of Earth that contain
living organisms
Notes: Constructive Vs. Destructive Forces
pg. 68
Lands are constantly being created and destroyed by
competing forces.
Constructive Forces
Destructive Forces
Forces that destroy and wear away
Forces that construct and shape
landmasses.
the land’s surface by building up
mountains and other land masses.
Examples:
Examples:
Notes: Earth’s Layers
pg. 71
How do Geologists Learn About Earth’s Layers?
A. They use two main types of evidence to learn about Earth’s
interior:
1.) direct evidence from rock samples
a. Geologists have drilled holes as deep as 12.3 km into
Earth.
b. The drills bring up samples of rock. These rocks give
geologists clues about Earth’s structure and conditions
deep inside Earth.
2.) indirect evidence from seismic waves.
a. When earthquakes occur, they produce seismic waves .
b. Geologists record the seismic waves and study how they
travel through Earth.
What Are the Features of Earth’s Layers?
B. The three main layers of Earth are the crust, mantle and core.
1.) The layers vary greatly in size, composition, temperature,
and pressure.
2.) The deeper down inside Earth, the greater the pressure.
3.) The temperature inside earth increases as depth increases.
C. The Layers of the Earth
1.) Crust – a layer of solid rock that includes both dry land and
the ocean floor (Earth’s outer skin)
a. Oceanic Crust – the crust that lies beneath the ocean;
mostly composed of basalt (a dark, fine-grained rock)
b. Continental Crust – the crust that forms the continents;
mostly composed of granite (a rock that is usually light in
color and has coarse grains)
2.) Mantle – a layer of rock that is solid, and very hot
a. Lithosphere – made up of the crust and upper mantle;
strong, hard and rigid rock
b. Asthenosphere – below the lithosphere; the material is
hotter and under more pressure; the material can bend
but is still considered a solid
3.) Core – below the mantle; made mostly of the metals iron a
nickel; consists of 2 parts
a. Outer Core – molten/liquid metals of iron and nickel
b. Inner Core – dense ball of solid metals iron and nickel
Pg. 70
Draw and Label the Layers of the Earth
Crust
Lithosphere
Asthenosphere
Mantle
Outer Core
Inner Core
Pg. 73
3 Types of Heat Transfer
1.) RADIATION – transfer of heat that is
carried in rays or waves
Examples :
2.) CONDUCTION – transfer of heat between
materials that are touching
Examples :
3.) CONVECTION – transfer of heat by the
movement of a fluid
Examples :
Convection Currents in Earth
• Heat from the core and the mantle itself causes convection currents
in the mantle.
• Mantle rock rises slowly from the bottom of the mantle toward the
top. The hot rock eventually cools and sinks back through the
mantle. Over and over the cycle of rising and sinking takes place.
• Convection currents like these have been moving inside Earth for
more than four billion years!
I. Plate Tectonics
A. ___Continental Drift______
1. Many early scientists have noticed
that the Earth’s continents seemed
to fit together.
2. ___Alfred Wegener____- proposed
the theory of continental drift
a. _Permian Period_ - about 225
million years ago
1.) all the continents formed a
supercontinent called
Pangaea
2.) ____Panthalassa____ was
the major ocean
b. __Triassic Period____ - Pangaea
was split in two
1.) _____Laurasia_____ in the
north (North America, Eurasia)
and Gondwanaland in the
south ( India, Africa, and
South America)
2.) Panthalassa broken in two,
one part becomes the
____Tethys Sea______
pg. 75
c. Wegner theorized that continents
moved horizontally to their present
location.
B. Evidence of Continental Drift
1. Fossil and Climate Clues
a. The reptile ___Mesosaurus____
1.) fossils found in South America
and Africa
2.) lived on land and water but
would have been impossible for
this animal to have swam across
an entire ocean
b. A fern _____Glossopteris________
1.) fossils found in Africa, Australia,
India, South America, and
Antarctica
2.) found in areas that vary greatly
in climate, scientists believe
these regions once were
connected and had similar
climates
c. Fossils of warm weather plants were
found in Arctic Ocean Islands
d. Glacial deposits have been found
where no glaciers exist today
2. Sea-floor Spreading
a. ___Mid-Ocean Ridge____1. using sound waves, scientists discovered a
system of underwater mountain ranges in
many oceans
2. The peaks of some of these mountains can
form an island
b. 1960’s scientist, _Harry Hess_, suggested a
theory of ___sea-floor spreading___
1. Magma gets forced upward through
cracks in the ocean floor
2. As new material comes up it pushes
sections of the sea floor away from the
ridge.
3. The magma solidifies and creates new sea
floor
c. Evidence for Sea-floor Spreading
1. Youngest rocks are located at the midocean ridge
2. Reversals of Earth’s magnetic field are
recorded by rocks in strips parallel to
ridges
Harry Hess
C. Plate Tectonics
1. Earth’s crust and upper mantle are broken
into sections called __plates_____
a. The crust and upper mantle are called
the ______lithosphere_________
b. Middle layer of the mantle is the
_asthenosphere__ - semi-molten rock,
very plastic-like
c. __Convection Currents__ inside Earth
cause plate tectonics – the cycle of
heating, rising, cooling, and sinking of
material inside Earth
2. Plate Boundaries
a. Divergent Boundary - two plates move
away from one another; ex. Sea-floor
spreading
b. Convergent Boundary -two plates move
toward each other, there are three types:
1.) subduction zone- dense ocean plate sinks
under light continental plate
ex: deep sea trench, volcanic mountain
chains
2.) two ocean plates collide
ex: deep sea trench, volcanic island chain
3.) two continental plates collide
ex: mountains, earthquakes common
c. Transform Fault Boundary two plates slide past each other; they can
move in opposite directions or in the same
direction
I. Plate Tectonics
A. _________________________
1. Many early scientists have noticed
that the Earth’s continents seemed
to fit together.
2. _____________________ - proposed
the theory of continental drift
a. __________________- about 225
million years ago
1.) all the continents formed a
supercontinent called
__________________
2.) _____________________ was
the major ocean
b. ___________________ - Pangaea
was split in two
1.) ____________________ in the
north (North America, Eurasia)
and ______________ in the
south ( India, Africa, and
South America)
2.) Panthalassa broken in two,
one part becomes the
_________________________
pg. 59
c. Wegner theorized that continents
moved horizontally to their present
location.
B. Evidence of Continental Drift
1. Fossil and Climate Clues
a. The reptile ____________________
1.) fossils found in South America
and Africa
2.) lived on land and water but
would have been impossible for
this animal to have swam across
an entire ocean
b. A fern ________________________
1.) fossils found in Africa, Australia,
India, South America, and
Antarctica
2.) found in areas that vary greatly
in climate, scientists believe
these regions once were
connected and had similar
climates
c. Fossils of warm weather plants were
found in Arctic Ocean Islands
d. Glacial deposits have been found
where no glaciers exist today
2. Sea-floor Spreading
a. _________________________1. using sound waves, scientists discovered a
system of underwater mountain ranges in
many oceans
2. The peaks of some of these mountains can
form an island
b. 1960’s scientist, ______________suggested a
theory of _________________________
1. Magma gets forced upward through
cracks in the ocean floor
2. As new material comes up it pushes
sections of the sea floor away from the
ridge.
3. The magma solidifies and creates new sea
floor
c. Evidence for Sea-floor Spreading
1. Youngest rocks are located at the midocean ridge
2. Reversals of Earth’s magnetic field are
recorded by rocks in strips parallel to
ridges
Harry Hess
C. Plate Tectonics
1. Earth’s crust and upper mantle are broken
into sections called ___________________
a. The crust and upper mantle are called
the ____________________________
b. Middle layer of the mantle is the
_________________- semi-molten rock,
very plastic-like
c. ______________________ inside Earth
cause plate tectonics – the cycle of
heating, rising, cooling, and sinking of
material inside Earth
2. Plate Boundaries
a. __________________- two plates move
away from one another; ex. Sea-floor
spreading
b. __________________-two plates move
toward each other, there are three types:
1.) subduction zone- dense ocean plate sinks
under light continental plate
ex: deep sea trench, volcanic mountain
chains
2.) two ocean plates collide
ex: deep sea trench, volcanic island chain
3.) two continental plates collide
ex: mountains, earthquakes common
c. _________________________two plates slide past each other; they can
move in opposite directions or in the same
direction