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FORCES
ON
EARTH
An investigation into how Newton’s Laws of Motion
are applied to the tectonic activity on Earth.
GEOLOGY

Geologists – scientists who study the forces that
make and shape the Earth

Geologists divide the forces that
change the Earth into two
categories:
•Constructive – shape the earth by
building up mountains and
landmasses
• Destructive – slowly wear
away mountains and every
other feature on Earth
SO….HOW DO WE KNOW
WHAT’S INSIDE THE EARTH?
•
Geologists record
seismic waves and
study how they travel
through the medium of
Earth.
• The speed and the
path the waves takes
reveal how the planet
is put together.
A JOURNEY TO THE CENTER OF THE EARTH
•
The further “in” you go… temperature
and pressure both increase
•
There are three main layers that make
up the Earth’s interior:
• Crust
• Mantle
• Core
THE CRUST
•
The layer of rock that
forms Earth’s outer skin
• It consists of about 10
miles of rock
• Continental crust is
thicker than oceanic
crust
• However, oceanic
crust is much denser
than continental crust
THE MANTLE
•
The mantle extends to a depth of
approximately 1,800 miles
• It is made of a thick solid rocky substance
•
The uppermost part of the mantle and the
crust together form a rigid layer called the
lithosphere
•
The asthenosphere is super-heated rock
(molten)
•
The remainder of the mantle is solid
Upper mantel
Lower mantel
Lithosphere (hard)
Asthenosphere (soft)
Mesosphere
THE CORE
•
Consists of two parts
• Outer core – molten iron and nickel metal
• Inner core – solid dense ball of iron and nickel metal
CONVECTION CURRENTS AND THE MANTLE
• Heat
is transferred through:
• Radiation
• Conduction
• Convection
RADIATION
•
Radiation – transfer of energy by
electromagnetic waves (ex. Sun heating the
Earth)
CONDUCTION
•
Conduction – heat by direct transfer of
particles of matter
CONVECTION
•
Convection - The transfer of heat energy by
movements of a fluid.
•
The heating and cooling of a fluid, changes in the
fluid’s density, and the force of gravity combine to set
convection currents in motion.
• Convection currents continue as long as heat is
added!
CONVECTION IN THE MANTLE
•
Heat from the Earth’s core and from the mantle itself cause the
convection currents in the mantle
•
Convection currents are an unbalanced force that causes heat
flow and the movement of material within the earth.
•
This moving material results in earthquakes and volcanic eruptions
to create mountains and ocean basins.
TECTONIC PLATES – WHAT ARE THEY?
•
The crust is broken into large pieces, which we call “plates”
PLATE MOVEMENT
•
Plate movement result in stress within the Earth’s crust which adds
energy to rock until the rock either breaks or changes shape
PLATES AND FORCES
•
Plates apply equal
and opposite
forces on each
other. (A push or
pull
)
•
The acceleration
of the plate
depends on forces
acting on the
plate and the
mass of the plate.
http://education.sdsc.edu/optiputer/flash/co
nvection.htm
EFFECTS OF PLATE TECTONICS
*There are several geological processes that occur
where plates meet (at the plate edges):
1. Volcanoes tend to erupt at plate margins as a result of
a process called subduction
2. Earthquakes occur where plates grind against or over
one other
3. Mountain building occurs as one plate is pushed over
another
4. Seafloor spreading occurs where two oceanic plates
pull apart, makes ocean basins
THE 3 TYPES OF PLATE
BOUNDARIES
“Convergent, means to come together.”
CONVERGENT BOUNDARIES
•
Convergent Boundaries are the boundaries between
two plates that are converging, or moving towards
each other.
•
Earthquakes, island formation, mountain forming,
and volcanoes all occur as the result of these plate
collisions.
• When two plates collide (converge) one plate moves
under the other.
This process is called “subduction.”
•
There are three types of convergent boundaries
TYPES OF CONVERGENT BOUNDARIES
Oceanic/oceanic
Subduction occurs
Oceanic/continental
Oceanic plate sinks
Continental/continental
Mountain ranges form
Convergent
boundary of two
oceanic plates.
Creates an island arc and
a trench.
A trench is like a deep
canyon, but in the ocean.
Example: Japan
The most famous trench in the world:
Mariana Trench
Oceanic plate and a
continental plate.
Forms a volcanic
mountain range and
a trench.
Example: Andes Mts
ContinentalContinental Boundary
The convergent
boundary of the
Eurasian and Indian
Plates has resulted in
the formation of the
highest mountain
range in the world –
The Himalayas
This illustration shows
the movement of the
land mass known as
India today. As it moved
on the Indian plate through
time, over millions of years,
it finally collided with the
Eurasian plate forming the
Himalayan Mountains
Mount Everest is the tallest mountain in the
world, at over 29,000 ft. and is part of the
Himalayas. This is a result of the Eurasian
and Indian Plates colliding and it is still
getting higher as these two plates continue
to collide.
DIVERGENT BOUNDARIES
•
Divergent Boundaries are the boundaries between
two plates that are diverging, or moving away from
each other.
“Divergent, means to spread apart.”
When plates are spreading apart from one another there is a lot
of geological activity. Earthquakes and volcanoes occur here.
•In some places like in East Africa, a rift valley can form that is
hundreds of feet deep.
Aerial
view of
Africa’s
Rift
Valley
The Mid-Atlantic Ridge is one of the
world’s largest divergent plates,
running North to South in just about
the center of the Atlantic Ocean.
All along this ridge, volcanic activity
takes place and the sea floor is
spreading East and West at a rate of
1.25 cm per year.
Question: So what is happening on the
other side of that same plate?
Divergent Boundary Between the
Eurasian and North American Plate
TRANSFORM FAULT BOUNDARIES
•
Transform Boundaries are the boundaries between two plates
that are sliding horizontally past one another.
“Transform, means to slide past one another.”
PLATES MOVE SIDE BY SIDE
•
Transform boundaries neither create nor consume crust.
Rather, two plates move against each other, building up
tension, then releasing the tension in a sudden and often
violent jerk. This sudden jerk creates an earthquake.
Earthquakes in Austin
Strike Slip Faults
Transform-fault boundary where the North American and Pacific plates
are moving past each other.
Example: San Andreas fault in California
The San Andreas Fault, seen
here, is the result of the Pacific
Plate sliding past the North
American Plate. This is the site
of many of the earthquakes that
occur in the United States
CHANGING EARTH’S SURFACE
•
Plate movement can alter Earth systems and
produce changes in Earth’s surface
• Deformation of the crust
• Faults
• Mountain building
• Land subsidence
• Volcanoes
VOLCANOES
•
A volcano is a weak spot in the crust where molten, rockforming magma comes to the surface
•
Volcanic activity builds mountains made of lava rock and
other volcanic materials
LOCATION OF VOLCANOES
•
There are more than 600 active volcanoes on land and many
more beneath the sea
•
Volcanic belts form along the boundaries of Earth’s plates.
• One major volcanic belt is the Ring of Fire
RING OF FIRE
Ring of Fire – very active region of subduction
http://www.vo
lcano.si.edu/p
layers.cfm?pid
=2
RECENT EARTHQUAKES AND VOLCANIC
ERUPTIONS
WHAT ARE HOT SPOTS?
•
All seismic activity occurs along plate boundaries
(except for hotspots)
•
Magma rises through the mantle forming an active
volcano
•
The plate moves over
this spot forming a
chain of islands with
the active volcano
being the one over
the hot spot
Hot Spot Volcanoes
HOW IT WORKS
WEB-QUEST!
•
Get a computer and
begin working on the
web-quest.
•
Follow the questions
and it will lead you
through the online
activities.
•
This is due –
A day: 3/12
B day: 3/13