Transcript 4.3 PPT_EQ & Waves

Warm up 9/29
1)
2)
3)
What is convection flow and how does this
lead to movement of lithospheric plates?
What creates convection flow?
Draw a diagram of convection flow. Label the
parts in your diagram.
1st block, 9/30
1.
2.
3.
Finish reading the Haiti Earthquake
article and answering the questions
Hand it in the black box when
finished.
You have 20 minutes
Warm-up 9/30, 4th block


List the three types of seismic waves
and describe one characteristic of
each type.
Put your name on this sheet of paper
and hand it in the black box up front.
Objectives
First…table of contents!
Unit 2: Earthquakes & Plate Tectonics
Date
Title
Page
9/22/14
Convection currents
and Plate Tectonics
Guided Notes with
Vocabulary
1
9/22/14
Plate Boundaries
Diagram
2
9/22/14
Tectonic Plates
Activity Sheet
3
9/29/2014
Volcanoes
and
Earthquake
Anatomy
Notes
4
5
Volcanoes

A volcano is mountain formed of
lava and/or pyroclastic material
Convergent boundaries

They can be caused by convergent
boundaries, in which plate
subduction forces magma to the
surface.
Divergent Boundaries

Volcanoes are also formed by
divergent boundaries because as
plates move apart, magma rises to
fill the gap.
Magma vs. Lava
Magma is molten rock found beneath
the Earth’s crust
Lava is molten that reaches the
surface and erupts from the volcano
Effects of volcanoes
1) Lahar- material that flows down the
volcano. It is a mixture of water and
rock fragments
Effects of volcanoes
2) Volcanic ash: fragments of material
that explode from the erupting volcano
What happened in Japan?
Tsunami hitting the coast:
http://www.youtube.com/watch?v=Yl0
8jK4ci2g

12
The red dots are locations of Earthquakes. Make an
observation and an inference about this map.
San Francisco 1989

SF Earthquake 1989 (longer)
What is a focus?
The point beneath the
Earth’s surface where
rock under stress breaks
to cause an earthquake.
What is an
epicenter?
The point on the
surface directly
above the focus.
The farther the distance
between the focus and the
epicenter, the weaker the
earthquake. Therefore,
the closer the focus is to
the surface, the stronger
the earthquake.
Distance from Focus to Epicenter
What is a fault?
It is the break in the crust
where the earthquake began,
between two blocks of rock
that have moved past each
other.
3 Types of Faults
Normal
Reverse
Strike-slip
When the hanging
wall drops down.
When hanging wall
moves up.
Walls move sideways
Creates forces that
pull the sides apart
Creates
compressional forces.
Horizontal forces
22
Quick Review
1) What causes an
earthquake?
2) Label the fault, epicenter,
and focus in the picture to
the right.
A=
B=
C=
b
a
c
What are seismic
waves?
Seismic waves are the
waves (vibrations)
caused by earthquakes
During an earthquake,
vibrations called seismic
wave move out from the focus
in all directions similar to the
ripples created by a pebble in
a pond.
Seismic waves carry the energy
of an earthquake away from the
focus, through the Earth’s
interior, and across the surface.
What are the three types
of seismic waves?



Primary waves
(P waves)
Secondary Waves
(S waves)
Surface waves (L waves)
Describe a P wave.
Travel the fastest
 Travel solids, liquids, and gases
 Move through the Earth at
different speeds, depending on
the density
 Called “push-pull” waves
(compress and expand the
ground like an accordion)

Describe an S wave.
Arrive at a given point after the
P waves
 Travel only through solids
 Move through solids at different
speeds depending on the density
 Cause rock particles to move
from side to side & up and down

Describe a L wave.
Slowest of the seismic
waves
 Move along the Earth’s
surface like waves travel in
the ocean
 Cause most of the damage
during an earthquake

When the P & S
waves reach the
surface, they move
more slowly creating
the most severe
ground movements.
What
do
scientists
use
to
Seismographs are used by
scientist
detect,
measure &
detecttoand
measure
record the vibrations of
earthquakes?
seismic waves.
An earthquake’s magnitude is a
measurement of its strength based
on seismic waves and movement
along faults.
https://www.youtube.com/watch?v=
Gbd1FcuLJLQ
Seismic Wave Demo
EQ & Seismic Wave Foldable


Let’s Fold and Label together
The directions for the inside of the
foldable is at your station
What are 3
rating scales
used to
measure an
earthquake?
Mercalli scale –
This scale rates
earthquakes by describing
their effects on people,
buildings, and the land
surface in a given
location.
Richter scale
This scale rates
earthquakes according to
the size of seismic waves
as measured by the
seismograph.
Moment Magnitude
scale
This scale rates earthquakes by
estimating the total energy
they release. The moment
magnitude scale can be used
to measure earthquakes of
all sizes, near or far!
How do scientists
determine the
location of an
earthquake’s
epicenter?
When an earthquake
strikes, P waves are the
first to arrive at a
seismograph followed by
the S waves.
 The farther away the
epicenter is, the greater
the difference between
the two arrival times.

This difference in time tells
scientists how far the
seismograph is from the
epicenter. This information
is then used to plot a circle
on a map.
The circle shows the
distance from one
seismograph station to all
points where the epicenter
could be located.
.

To determine the exact
location of the epicenter, at
least THREE stations need to
find their distance from the
epicenter and draw a circle
on a map
The single point
where the 3 circles
intersect is the
location of the
earthquake’s
epicenter.
Video
https://www.youtube.com/watch?v=M
y5ootSNbak