Review
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Earthquakes
Types of
Faults
Where do
they
Occur?
The Film
Earths
Structure
Predictions
Measuring
Review
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Where do they occur?
Plate Tectonics
Hazard Zones
Review
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World Plate Boundaries
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Transform
plate
boundaries
Divergent Plate
Boundaries
Click for a
detailed map
Convergent
plate
boundaries
Boundary Table
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Table of Tectonic Plate Boundaries
Boundary Type
Plate Motion
Regional Stress
Main Fault Type
Landform
Divergent
Tension
Normal
Mid-Ocean Ridges
Transform
Shear
Strike-Slip
Transverse Mntns
Convergent
Compression
Thrust
Oceanic Trenches
Volcanic Arcs
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Tectonics
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Divergent Plate Boundaries
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where two plates move away from each other . Most of the world's divergent plate
boundaries are on the ocean floor, in the form of mid-ocean spreading ridge. At
divergent boundaries, the two plates are continually moving apart, heading in
opposite directions away from each other.
Divergent
Illustration
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Tectonics
Review
Divergent Plate Illustration
Mid-Ocean spreading in the
deep ocean basins where the
plates move apart. As they
separate, hot lava from the
mantle rises between them.
This lava gradually cools,
contracts, and cracks,
creating faults.
Most are shallow
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Tectonics
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Review
Transform Plate Illustration
Where plate slide
horizontally against each
other. These can also be
caused by soil liquefaction
(where the soil acts like
liquid)
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Tectonics
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Review
Transform Plate Boundaries
Where two plates move horizontally side-by-side in
opposite directions. Transform plate boundaries are
strike-slip faults. As the two plates slide next to each
other, trying to move in opposite directions, there is
much friction and stress between them. As a result,
transform plate boundaries are zones of frequent
earthquakes.
Transform
Plate
Illustration
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Convergent plate boundaries
Where two plates move toward each other and
either collide with each other or one plate
bends down and goes beneath the other.
Convergent
plate animation
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Convergent plate Illustration
Called Sub-duction zones these
comprise approximately 80% of
major quakes. The famed Ring of
Fire is included. One plate is thrust
under another.
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Tectonics
Review
Hazard Zone
Areas with frequent activity
The famed Ring of Fire
Steps to Safety
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Review
Our Violent Home
Safety
Review
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Make an earthquake preparedness kit!
Food, water, matches, flashlight,
batteries, blankets and SHOES! All will be
very hard to come by following a large
earthquake!
Public Domain
Take action during an earthquake and
remember to ‘Drop’, ‘Cover’ and ‘Hold On’.
Move outside and away from buildings after
the shaking.
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Zone
Review
EARTHS STRUCTURE
Compositional
Layers
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Mechanical
Layers
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Compositional Layers
Crust
Mantle
Core
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Structure
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Mechanical Layers
Lithosphere
Aesthenosphere
Inner
Core
Outer
Core
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Structure
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Crust
The outer layer of the Earth.
Continental crust is thick (25-50 km thick), low in density, and has an
intermediate average composition.
Oceanic crust is thin (typically 5-10 km thick), higher in density, and has a
mafic average composition
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Structure
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Mantle
The layer located above the Core and below the Crust it begins about 6
miles(10 km) below the oceanic crust and about 19 miles (30 km) below
the continental crust. It is about 1,800 miles (2,900 km) thick and makes
up about 80% of Earth’s total volume
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Structure
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Core
Although we have no samples to look at Seismic waves
suggest a very dense molten metallic core.
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Outer Core
Is scorching hot and electrically conductive liquid. It is
where Earth’s magnetic field is generated.
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Structure
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Lithosphere
which is a rigid layer that is broken up into tectonic plates
and averages about 100 km (60 miles) thick.
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Structure
Review
Aesthenosphere
The layer beneath the lithosphere is the weak, soft
Aesthenosphere, which is roughly 300 to 400 km thick
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Structure
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Review
Measuring Earthquakes
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The vibrations produced by earthquakes are detected, recorded, and
measured by instruments called seismographs. The line made by a
seismograph, called a "seismogram," show the changing intensity of the
vibrations by responding to the motion of the ground. From this scientists
can determine the time, the epicenter, the focal depth, and the type of fault
of an earthquake.
There are two main types of scales used in connection to Earthquakes. The
Mercalli and the Richter.
The Mercalli
Scale
The Richter
Scale
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The Richter Scale
In 1935, Charles F. Richter devised a way to record quake
activity by measuring the size of the seismic waves caused
by the shifting earth. These impressions are recorded on a
device known as a seismograph, and much can be told from
this mechanism. This graph can measure the date and time,
along with the exact central location of these troubling
disasters. They in turn, are then ranked in terms of severity
on the world famous
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The Mercalli Scale
One way to measure the strength of an earthquake is to use
the Mercalli scale. Invented by Giuseppe Mercalli in 1902,
this scale uses the observations of the people who
experienced the earthquake to estimate its intensity.
.
Review
Predictions
Scientist use past occurrences to determine the likelihood of
quakes. Very little improvement has been made in the accuracy of
these predictions over the last half century.
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Review
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Whose Fault is it?
The crustal plates are being deformed by stresses . The ground will first
bend, then upon reaching a certain limit, breaks and “snaps” to a new
position. There are a couple main types of faults which cause
earthquakes.
Strike-Slip
Fault
Dip-Slip
Fault
Review
Strike-Slip Fault
Strike-Slip faults move horizontally and form from Shear stress.
Strike-Slip
Fault
Animation
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Review
Dip-Slip Fault
Dip-Slip faults move vertically. One side moves up while the other
moves down.
Dip-Slip
Fault
Animation
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Review
Strike-Slip Fault
Animation
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Dip-Slip Fault
Animation
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Back to
Measuring
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Back to
Measuring
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The Film
Devastation
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Quiz Question 1
Which of the below is a way to measure
earthquake intensity?
The Mashall Scale
The Mercury Scale
The Mecalis Scale
REVIEW
† Both the Mercalli and Richter scale are used to Measure Earthquakes.
† Two plates moving horizontally (side by side) form Transform
boundaries and are active areas for Earthquakes.
† Stop Drop and Cover! Is the safety motto for Quake preparedness
† There are 3 major plate environments on Earth.
† The Lithosphere is 60 miles thick and is where most earthquakes occur.
REVIEW
† Mid-Ocean Ridges form from Divergent boundaries.
† Nearly 80% of major Quakes form from Convergent boundaries
† The crust forms a thin outer layer on Earths surface.
† Earthquake prediction has not changed much over the last 20 years.
† What we have learned about the core is not from direct observation .
† What we have learned about the core is not from direct observation .
Quiz Question 2
How many Major types of Plate
environments exist?
2
4
3
Quiz Question 3
Prediction has evolved dramatically over the
last 20 years.
True
False
Quiz Question 4
This layer is on average 60 miles thick and
most earthquakes occur here.
Inner Core
Aesthenosphere
Lithosphere
Quiz Question 5
When 2 plates move horizontally in opposite
direction. This type of boundary forms.
Inoppositum
Divergent
Transform
Quiz Question 6
The Mid-Ocean ridges are formed by what
type of boundary.
Convergent
Ridgitum
Divergent
Quiz Question 7
80% of major Earthquakes are caused by
what type of boundary?
Diemuchium
Transform
Convergent
Quiz Question 8
Stop! Drop! Roll is the motto for Earthquake
safety.
False
True
Quiz Question 9
The Outer layer of the Earth structure is?
Outersphere
Mantle
Crust
Quiz Question 10
We have specific and direct observations of
the Earth’s core.
True
False
USGS: Earthquake Center. (2007, March
20). Retrieved May 4, 2010, from United
States Geologic Survey:
http://earthquake.usgs.gov/earthquakes/
United States Geologic Survey. (n.d.). USGS
Astrogeology Research Program. Retrieved
May 4, 2010, from
http://astrogeology.usgs.gov/
This Dynamic Earth: Developing the Theory.
(2007, February 7). Retrieved May 4, 2010,
from United States Geologic Survey:
http://pubs.usgs.gov/gip/dynamic/developi
ng.html
Dub Long Photo Library
(2010)
Arranged
By
Dub Long
glong@nwacc.edu