An investigation into how Newton’s Laws of Motion are applied to the tectonic activity on Earth.
FORCES ON
EARTHUNIT 3.2
USE THESE NOTES:
• What do you know about our planet?
OUR HOME – PLANET 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 take reveal how the planet is put together.
• The interior of the earth is hot.
• Convection currents are an unbalanced force in the mantle that cause heat flow and movement of material within the earth
• This results in plate movement that causes earthquakes and volcanic eruptions to create mountains and ocean basins.
• Let’s take a closer look at our Earth
THE EARTH IS HOT, HOT HOT!
• The further “in” you go… temperature and pressure both increase
• There are four main layers that make up the Earth’s interior:
• Crust
• Mantle
• Core –
split into outer
and inner core
A JOURNEY TO THE CENTER OF THE EARTH
• 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 CRUST
• The mantle extends to a depth of approximately 1,800 miles
• It is made of a thick solid rocky substance composed of mostly silicates—a wide variety of compounds that share a silicon and oxygen structure
• The uppermost part of the mantle and the crusttogether form a rigid layer called the lithosphere
• The asthenosphere is super-heated rock (molten)
• The remainder of the mantle is solid
THE MANTLEUpper mantel
Lower mantel
Lithosphere (hard)
Asthenosphere (soft)
Mesosphere
• Consists of two parts
• Outer core – molten iron and nickel metal
• Inner core – solid dense ball of iron and nickel metal
THE CORE
• Heat is transferred through:• Radiation• Conduction• Convection
• Let’s go through what each type of heat is first, before we apply it to the Earth.
HEAT TRANSFER (THE MOVEMENT OF HEAT)
• Radiation – transfer of energy by electromagnetic waves (ex. Sun heating the Earth)
RADIATION
• Conduction – Conduction transfers heat via direct molecular collision. Occurs via physical contact.
• When you touch a pan that is on the stove, the fire's heat causes molecules in the pan to vibrate faster, making it hotter. The heat is transferred to your hand when you touch the handle.
CONDUCTION
• Convection - The transfer of heat energy by movements of a fluid. (air, liquids and molten material are all considered “fluid”)
• Heat moves (transfers) because the density of the fluid changes. Hot things are lighter. The fluid moves away from the heat source.
• Then by being away from the heat source, it begins to cool
• Again, it’s density changes, it becomes heavier
• Heavy things sink, so it sinks back down, and it goes near the heat source again and the cycle repeats.
• Convection currents continue as long as heat exists!
CONVECTION
• 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.
CONVECTION IN THE MANTLE
• The crust is broken into large pieces, which we call “plates”
TECTONIC PLATES – WHAT ARE THEY?
• Plate movement result in stress within the Earth’s crust which adds energy to rock until the rock either breaks or changes shape
PLATE MOVEMENT
• Plates apply equal and opposite forces on each other. (A push or pull, shown by )
• The acceleration of the plate depends on forces acting on the plate and the mass of the plate.
PLATES AND FORCES(AND NEWTON’S LAWS)
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 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.
• The type of stress at this boundary is “compression”
• When two plates collide (converge) one plate moves under the other.This process is called “subduction.”
• There are three types of convergent boundaries
“Convergent, means to come together.”
TYPES OF CONVERGENT BOUNDARIES
Oceanic/oceanic
Subduction occurs (you
will add examples in a
minute, leave enough
space for that)
Oceanic/continental Oceanic plate sinks under
the less dense plate
Continental/continentalEqual density plates
collide
Let’s look at a few examples:
WHAT CAN HAPPEN AT EACH BOUNDARY?
There are 3 types
of convergent
boundaries:
1. Convergent
boundary of two
oceanic plates.
Forms an island arc and
a trench.
A trench is like a deep
canyon, but in the ocean.
Example: Japan
Mariana Trench
The most famous trench in the world:
Convergent
Boundary 2:
Oceanic plate and
a continental plate.
Forms a volcanic
mountain range and
a trench.
Example: Andes Mts
Convergent Boundary 3:
Continental-Continental
Convergent Boundary (also
called a Collisional Boundary)
Forms mountains - 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.
• The type of stress is “tension”
“Divergent, means to spread apart.”
When plates are spreading apart from one another there is a lot of
geological activity. Earthquakes and volcanoes can occur here.
•In some places like in East Africa, a rift valley can form that is
hundreds of feet deep. 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?
Another Example: 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.
• The type of stress is “shear-stress”
“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
There is a transform-fault boundary where the North American and Pacific
plates are moving past each other.
This is the: San Andreas fault in California
Strike Slip Faults
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
• Plate movement can alter Earth systems and produce changes in Earth’s surface
• Deformation of the crust
• Faults
• Mountain building
• Land subsidence (lands sinks)
• Volcanoes
CHANGING EARTH’S SURFACE
• A volcano is a weak spot in the crust where molten, rock-forming magma comes to the surface
• Volcanic activity builds mountains made of lava rock and other volcanic materials
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
LOCATION OF VOLCANOES
Ring of Fire – very
active region of
subduction, where is
it located?
RING OF FIRE
http://www.volcano.si.edu/players.cfm?pid=2
RECENT EARTHQUAKES AND VOLCANIC ERUPTIONS
• 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
WHAT ARE HOT SPOTS?
Hot Spot Volcanoes
EARTH’S INTERIOR G.O.
• Get a computer and begin working on the web-quest.
• Follow the questions and it will lead you through the online activities.
• When is this due??
• (You will have next class to work on this as well)
WEB-QUEST!
• Get a computer and begin working on the web-quest.
• Follow the questions and it will lead you through the online activities.
• When is this due?
WEB-QUEST!