Title: Earthquakes: What are they and what causes them to happen?
1Earthquakes What are they and what causes them
to happen?
Shake, Rattle, and Roll!
- Mrs. Hornsbys Fifth Grade Class
2Table of Contents
- Georgia Performance Standards
- What is an Earthquake?
- What are Earths layers?
- What are Plate Tectonics?
- What Happens When Plates Move?
- Types of Plate Boundaries
- The Theory of Continental Drift
- What is a Fault?
- What Happens when an Earthquake Starts?
- How are Earthquakes Measured?
- The Richter Magnitude Scale
- How Long Does an Earthquake Last?
- How Many Earthquakes Happen Each Year?
- Where Do Earthquakes Occur Most Often in the
United States? - The 25 Largest Earthquakes in the United States
- Famous Earthquakes Around the World
- Photos of Earthquake Damage
- What Have You Learned?
- References
3Georgia Performance Standards
- S5Cs4 Students will use ideas of system, model,
change, and scale in exploring scientific and
technological matters. - S5E1 Students will identify surface features of
the Earth caused by constructive and destructive
processes. - S5P1 Students will verify that an object is the
sum of its parts. - M5D1 Students will analyze graphs.
- M5N5 Students will understand the meaning of
percentage
4What is an Earthquake?
- An earthquake is a shaking of the ground caused
by a sudden release of energy in the Earths
crust. More than a million of them occur each
year! However, most are too small to be felt or
to cause damage. Click the picture below to watch
a video about earthquakes.
5What are Earths Layers?
- The Earths crust is the outer layer and is made
of rock. It is very thin compared to the other
layers. - The mantle is the very hot layer of rock beneath
the crust. No one has ever been to the mantle,
but rock from the mantle sometimes reaches the
Earths surface through volcanoes. - The outer core is made of liquid, or molten iron.
- The inner core is made of solid iron. Even though
the core is the hottest layer, great pressure at
the center of the Earth keeps the inner core
solid.
Inner Core
Outer core
Mantle
Crust
6What are Plate Tectonics?
- Earths surface is made up of many plates that
float on the soft rock of the mantle. As the
mantle moves, the plates also move. - Plates move only a few centimeters each year.
- When one plate moves, it affects the other
plates. - As plates move around, they cause great changes
in the Earths surface, such as mountains,
valleys, volcanoes, and earthquakes!
7What Happens When Plates Move?
8Types of Boundaries
Wegeners Theory of Continental Drift
9What is a Fault?
- Many earthquakes occur along faults in the
Earths crust. A fault is a place where pieces of
the plates move. - A normal fault is where tension weakens the
crust until the rock fractures, and one rock
moves downward from another. This occurs when two
plates are pulling apart, as in a divergent
boundary. - A strike-slip fault is where two blocks of rock
are moving past each other horizontally, as in a
transform boundary. The famous San Andreas Fault
is a strike-slip fault. - A Reverse fault is where a fault block is forced
upward, usually during a collision with another
block, as in a convergent boundary.
10What Happens When an Earthquake Starts?
- The sudden release of energy from an earthquake
sends out several different shaking movements, or
seismic waves. - Surface waves are ripples of energy that spread
outward when rocks slip past each other along a
fault, just like throwing a stone into a calm
pond. - Body waves are seismic waves that travel through
material rather than over its surface. There are
two types of body waves P-waves and S-waves. - The P-wave is also known as the sound wave. It
travels through the interior of the Earth rather
than over the surface as a series of squeezes and
stretches. P-waves reach everywhere around the
Earth after about 20 minutes. - The S-wave, or shear wave, produces a shaking
motion, like if you tied a rope to a poll and
shook the other end side to side. S-waves can
only travel in solid material.
11How are Earthquakes Measured?
- Earthquakes are measured by instruments called
seismographs. It has a base that sets firmly in
the ground, and a heavy weight that hangs free.
When an earthquake causes the ground to shake,
the base of the seismograph shakes too, but the
heavy weight does not. The spring that it is
hanging from absorbs all the movement. The
seismograph records the difference in position
between the shaking part and the motionless part. - The recording is called a seismogram. It is used
to determine how large the earthquake was. A
short wiggly line that wiggles very little means
a small earthquake. A long wiggly line that
wiggles a lot means a large earthquake.
12The Richter Magnitude Scale
Description Richter Magnitudes Earthquake Effects
Micro Less than 2.0 Microearthquakes, not felt.
Very Minor 2.0-2.9 Usually not felt, but recorded.
Minor 3.0-3.9 Often felt, but rarely causes damage.
Light 4.0-4.9 Noticeable shaking of indoor items, rattling noises. Significant damage unlikely.
Moderate 5.0-5.9 Can cause major damage to poorly constructed buildings over small regions. Slight damage to well-designed buildings.
Strong 6.0-6.9 Can be destructive in areas up to about 100 miles across in populated areas.
Major 7.0-7.9 Can cause serious damage over larger areas.
Great 8.0-8.9 Can cause serious damage in areas several hundred miles across.
Rare Great 9.0 or greater Devastating in areas several thousand miles across.
13How Do Scientists Know Where an Earthquake Has
Happened?
- The location below the Earths surface where the
earthquake starts is called the hypocenter. -
- The location directly above the hypocenter on the
Earths surface is called the epicenter. - It take three seismographs to locate an
earthquake. Scientists draw a circle on a map
around the three seismographs where the radius of
each is the distance from the station to the
earthquake, the intersection of those three
circles is the epicenter.
14How Long Does an Earthquake Last?
- Sometimes an earthquake has foreshocks. These are
smaller earthquakes that happen in the same place
as the larger earthquake. - The largest, main earthquake is called the
mainshock. -
- Mainshocks always have aftershocks that follow.
These are smaller earthquakes that occur
afterwards in the same place as the mainshock.
Depending on the size of the mainshock,
aftershocks can continue for weeks, months, or
even years after the mainshock!
15Famous Earthquakes Around the World
- San Francisco, California April 18, 1906
- (Magnitude About 8)
- Tokyo, Japan September 1, 1923
- (Magnitude about 8.25)
- Chile May 22, 1960
- (Magnitude About 9)
- Anchorage, Alaska March 27, 1964
- (Magnitude About 8.5)
16How Many Earthquakes Happen Each Year?
17Where do Earthquakes Occur Most Often in the
United States?
18Top 25 Earthquakes in the United States
(Percentage)
19Earthquake Damage
20What Have You Learned?
Click Here To review the Brain Pop video and
take the quiz!
Click Here To test your knowledge about
earthquake vocabulary!
21References
- http//earthquake.usgs.gov/learning/kids.php
- http//www.exploratorium.com/faultline/
- http//teacher.scholastic.com/activities/wwatch/ea
rthquakes/ - http//www.fema.gov/kids/quake.htm
- http//www.ditto.com/default.aspx
- Earthquake Statistics
- The Largest Earthquakes in the United States
- http//www.brainpop.com
- Mountains, Volcanoes, and Earthquakes Harcourt
Earth Science Grade 5, p. C14.