CHAPTER 1: PLATE TECTONICS
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Earth’s Interior
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Convection and the Mantle
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Drifting Continents
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Sea-Floor Spreading
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The Theory of Plate Tectonics
F.1.1.1 Explain how geologists learn about Earth’s inner structure.
F.1.1.2 Identify the characteristics of Earth’s crust, mantle, and core.
EARTH’S INTERIOR
Geologists have used two main types of evidence to learn about
Earth’s interior: direct evidence from rock samples and indirect
evidence from seismic waves.
Rocks from inside Earth give geologists clues about Earth’s
structure.
Using data from seismic waves produced by earthquakes,
geologists have learned Earth’s interior is made up of several layers.
EARTH’S INTERIOR
EARTH’S INTERIOR
The crust is the layer of rock that forms
Earth’s outer skin. The crust is a layer of
solid rock that includes both dry land and
the ocean floor.
Oceanic crusts consists mostly of rocks
such as basalt. Continental Crust, is
mostly made up of granite.
EARTH’S INTERIOR
The Mantle is a layer of hot rock. Earth’s mantle is made up of rock
that is very hot, but solid. Scientists divide the mantle into layers
based on the physical characteristics of those layers.
The uppermost part of the mantle and the crust together form a
rigid layer called the lithosphere. Below the lithosphere is a soft
layer called the asthenosphere. Beneath the asthenosphere, the
mantle is solid.
EARTH’S INTERIOR
The core is made mostly of the metals iron and nickel. It consists of
two parts – a liquid outer core and a solid inner core. The outer
core is a layer of molten metal that surround the inner core. The
inner core is a dense ball of solid metal.
Scientists think that movements in the liquid outer core create
Earth’s magnetic field. Because Earth has a magnetic field, the
planet acts like a giant bar magnet. (Keeps us in orbit)
EARTH’S INTERIOR
F.1.2.1 Explain how heat is transferred.
F.1.2.2 Identify what causes convection currents.
F.1.2.3 Describe convection currents in Earth’s mantle.
CONVECTION AND THE MANTLE
There are three types of heat transfer: radiation, conduction, and
convection.
CONVECTION AND THE MANTLE
Radiation is the transfer of energy through empty space.
Sunlight warming Earth’s surface, or a microwave.
CONVECTION AND THE MANTLE
Conduction is heat transfer by direct contact of particles of matter.
CONVECTION AND THE MANTLE
Convection is the transfer of heat by the movement of a heated
fluid.
CONVECTION AND THE MANTLE
The flow that transfers heat within a fluid is called a convection
current. The heating and cooling of the fluid, changes in the fluid’s
density, and the force of gravity combine to set convection
currents in motion.
Convection currents flow in the mantle. The heat source for
these currents is heat from Earth’s core and from the mantle itself.
CONVECTION AND THE MANTLE
CONVECTION AND THE MANTLE

F.1.3.1 Explain Alfred Wegener’s hypothesis about the continents.

F.1.3.2 List the evidence used by Wegener to support his
hypothesis.

F.1.3.3 Explain why other scientists of Wegener’s time rejected his
hypothesis.
DRIFTING CONTINENTS
 Alfred
Wegener wondered why the coasts of
several continents matched so well.
Wegener’s hypothesis was that all the continents had
once been joined together in a single landmass and
have since drifted apart. The Super-continent was
named Pangaea – “all lands”.
 Pangaea existed 300 million years ago, and over tens of
millions of years, Pangaea broke apart and drifted to
their present-day locations, becoming the seven
continents today: North America, South America,
Africa, Australia, Antarctica, Europe, and Asia.

DRIFTING CONTINENTS
DRIFTING CONTINENTS
DRIFTING CONTINENTS

Simulation of moving plates:
http://www.enchantedlearning.com/subjects/astronomy/planets/e
arth/Continents.shtml
DRIFTING CONTINENTS

The idea that the continents slowly moved over Earth’s Surface
became known as the continental drift. Wegener presented
evidence to support his theory:
1.
Mountain Ranges and landforms provide evidence for
continental drift. Mountain ranges in South America and
Africa line up. Also, European coal fields match with similar
coal fields in North America. We know coal is a product of
once living, animals and plants.
DRIFTING CONTINENTS
2.
Evidence from Fossils: Fossils of the plant Glossopteris has been
found in rocks on widely separated landmasses. Additionally,
fossils of the reptiles Mesosaurus and Lystrosaurus also have
been found on widely separated landmasses.
3.
Evidence from the Climate: An island in e Artic Ocean
contains fossils of tropical plants. The island at one time must
have been close to the equator. Also, scratches in rocks
made by glaciers have been found in South Africa. Wegener
stated Earth’s climate has not changes, but the positions of the
continents have changed.
DRIFTING CONTINENTS

Wegener could not provide a satisfactory explanation for the
force that pushes or pulls the continents. Most geologists
rejected his theory. Due to new evidence, Wegener’s theory is
being reconsidered.
DRIFTING CONTINENTS

F.1.4.1 What is the process of sea-floor spreading?

F.1.4.2 What is the evidence for sea-floor spreading?

F.1.4.3 What happens at deep-ocean trenches?
SEA-FLOOR SPREADING

Scientists mapped the mid-ocean ridge using sonar.

Mid-Ocean ridge is the longest chain of mountains in the world,
curving along the sea floor of all Earth’s oceans.

Sonar is a device that bounces sound waves off underwater objects
and then records echoes of these sound waves.
SEA FLOOR SPREADING
Earth’s ocean floors move like a conveyor belt, carrying the continents
with them. This movement begins at the mid-ocean ridge.
The ridge forms along a crack in the oceanic crust. At the mid-ocean
ridge, molten material rises from the mantle and erupts. The molten
material then spreads out, pushing older rock to both sides of the
ridge.
SEA FLOOR SPREADING

Then more molten material splits apart the strip of rock, pushing it
aside. This process, called sea-floor spreading, continually adds
new material to the ocean floor.
SEA FLOOR SPREADING
SEA-FLOOR SPREADING
1.
Scientists have found strange rocks shaped like
pillows in the central valley of the mid-ocean ridge.
Such rocks can form only if molten material hardens
quickly after erupting under water.
2.
Scientists discovered that the rock that makes up
the ocean floor lies in a pattern of magnetized strips.
3.
Lastly, the last piece of evidence came from rock
samples, the farther from the ridge the rocks were
taken, the older they were.
EVIDENCE
http://kids.earth.nasa.gov/archive/pangaea/evidence.html
EVIDENCE – FURTHER READING
 The
ocean floor does not just keep spreading,
it also sinks beneath deep underwater
canyons called deep-ocean trenches.
 Where
there are trenches, subduction takes
place. Subduction is the process by which the
ocean floor sinks beneath a deep-ocean
trench and back into the mantle. This
happens over tens of millions of years.
SEA FLOOR SPREADING

The process of subduction and sea-floor spreading can change
the size and shape of the oceans. Because of these processes,
the ocean floor is renewed about every 200 million years.

The Pacific Ocean is shrinking.

The Atlantic Ocean is expanding.
SEA-FLOOR SPREADING

F.1.5.1 Explain the theory of plate tectonics

F.1.5.2 Describe the three types of plate tectonics.
THE THEORY OF PLATE TECTONICS

Earth’s lithosphere is broken into separate sections called plates.
The plates fit closely together along cracks in the crust.
THEORY OF PLATE TECTONICS
THE THEORY OF PLATE TECTONICS

Plate Tectonics is the geological theory that states pieces of the
Earth’s lithosphere are in constant, slow motion, driven by
convection currents in the mantle. The theory of plate tectonics
explains the formation, movement, and subduction of Earth’s
plates.
THE THEORY OF PLATE TECTONICS

Two plates move apart – these occur mostly at the mid-ocean
ridge. (creation of valleys)
DIVERGENT BOUNDARY
DIVERGENT BOUNDARY

Two plates come together causing a collision.
CONVERGENT BOUNDARY
CONVERGENT
A
place where two plates slip past each other,
moving in opposite directions. Earthquakes
occur frequently along these boundaries.
TRANSFORM BOUNDARY
 The
LAGEOS II satellite, built by the Italian
Space Agency, Agenzia Spaziale Italiana
(ASI), and managed by NASA's Goddard
Space Flight Center, measures crustal
movement by using Satellite Laser Ranging
technology
TODAY – NASA’S ROLE
 Residents
of warm southern California are moving to
Alaska whether they like it or not. Scientists, using the
theory of plate tectonics, say that southern California
is moving north and will collide with Alaska in
approximately 150 million years.
TODAY

What can scientists predict about some of the features of
the Earth existing today? Quite a lot. The Atlantic Ocean
will continue to expand, while the Pacific Ocean (originally
Panthalassa Ocean) will shrink. Eventually, the
Mediterranean Sea (remnant from the Tethys Sea) will
disappear, connecting Africa with Europe. India will
continue to push into the southern Asian continent, pushing
the Himalayas higher. Meanwhile the city of Los Angles will
continue its journey north to join with the city of San
Francisco. This will take several million years to occur.
Maybe in another 200 million years there will be no need for
a transoceanic trip from America to Asia.
PREDICTIONS FOR THE FUTURE:

Lab: Mapping a future world or modeling plate boundaries

Review Prep – Chapter One

Review (1-10) page

Test Prep (Terra Nova) 1-5

Review Sheet

Review for Chapter One

Chapter One Assessment
CHAPTER ONE – PLATE TECTONICS