This presentation was used for a year 8 Natural Disaster unit. Unfortunately the graphics are not able to be used in this format.

1. EARTHQUAK
ES
Toolbox

2. What we will be studying today:
 The Earth’s structure
 What are Tectonic plates and what do they
have to do with an Earthquake?
 The different types of plate boundaries.
 What is an Earthquake? How does it occur?
 How do we measure an Earthquake?
 Can we predict Earthquakes?
 What are the impacts of an Earthquake?

3. The Earths Structure
 The earth consists of several layers. The three
main layers are the core, the mantle and the
crust. The core is the inner part of the earth,
the crust is the outer part and between them is
the mantle.

4. Cross section of the Earth

5. Cross section of the Earth

6. Tectonic Plates
Before we can understand Tectonic plates, lets take a
look at Continental drifts:
 In 1912, a German scientist called Alfred Wegener
proposed that South America and Africa were once
joined together and had subsequently moved apart.
 He believed that all the continents were once joined
together as one big land mass called Pangaea and
this was intact until about 200 million years ago.
 The idea that continents are slowly shifting their
positions is called continental drift.

7. Continental drift

8. Tectonic Plates
 What are Tectonic plates?
the two sub-layers of the earth's crust (lithosphere) that move,
float, and sometimes fracture and whose interaction causes
continental drift, earthquakes, volcanoes, mountains, and oceanic
trenches.
the two sub-layers of the earth's crust (lithosphere) that move,
float, and sometimes fracture and whose interaction causes
continental drift, earthquakes, volcanoes, mountains, and oceanic
trenches
The ocean floors are continually moving, spreading from the
centre and sinking at the edges.
At the edges of these plates (plate boundaries) earthquakes and
volcanoes occur.
Convection currents in the mantle move the plates. The source of
heat driving the convection currents is radioactive decay which is
happening deep in the Earth.

9. Two Types of Plates
Oceanic Plates Continental Plates
Oceanic plates, as the name goes, Continental plates are crust that
are crusts which 'carry' the have continents (Large land
oceans above it. It is made of masses) and some areas of
lighter but denser materials than ocean on them. They are usually
the continental crust. named after the continents they
'carry'. Because they are made
of lighter and less dense
substances than an oceanic
plate

10. Plate names
North Eurasian
American
Pacific Pacific
African
South
Nazca American Indo-Australian
Plate
Antarctic

11. Earthquakes
What are they? How do they Occur?
 Earthquakes are vibrations caused  When two blocks of rock or two
by earth movements at plate plates are rubbing against each
boundaries and at major fault lines other, they stick a little. They
(cracks in the earth’s surface).
don't just slide smoothly; the
rocks catch on each other. The
rocks are still pushing against
each other, but not moving. After
a while, the rocks break because
of all the pressure that's built up.
When the rocks break, the
earthquake occurs. During the
earthquake and afterward, the
plates or blocks of rock start
moving, and they continue to
move until they get stuck again.

12. What are the different Tectonic
Plate Boundaries that cause
Earthquakes?
Divergent Boundaries: At divergent boundaries new crust is created as
two or more plates pull away from each other. Oceans are born and
grow wider where plates diverge or pull apart. As seen below, when a
diverging boundary occurs on land a 'rift', or separation will arise and
over time that mass of land will break apart into distinct land masses
and the surrounding water will fill the space between them. The
pressure from the break and heat from the rising lava can cause an
earthquake

13. Why do the plates move?
The plates that form the crust of the earth are floating on the molten interior
of the planet, and they are constantly moving and pushing each other
because of the heat escaping.

14. What are the different Tectonic
Plate Boundaries that cause
Earthquakes?
 In plate tectonics, a convergent boundary, also known as a destructive plate
boundary is an actively changing region where two (or more) tectonic plates
move toward one another and collide. The oceanic plate descends under the
continental plate because it is denser. As the plate descends it starts to melt
due to the friction caused by the movement between the plates.
 As a result of pressure, friction, and plate material melting in the mantle,
earthquakes and volcanoes are common near convergent boundaries. When
two plates move towards one another, they form either a subduction zone or
a continental collision.

15. What are the different Tectonic Plate
Boundaries that can cause
Earthquakes?
 Conservative plate margins
At a conservative margin two plates try to slide
past each other slowly. Quite often, the two
plates stick and pressure builds up; the
release of this pressure creates a severe
earthquake.

16. Conservative plate boundary

17. How is an Earthquake
Measured?
This measures the magnitude of a tremor (how powerful it
is) using an instrument called a seismograph.
On the Richter Scale, magnitude is expressed in whole
numbers and decimal fractions. Although the Richter Scale
has no upper limit, the largest earthquake ever recorded
was in 1960 in Chile. It measured 9.5 on the Richter Scale.
It is a logarithmic scale which means that a size ‘6’ on the
Richter Scale is 10 times larger than a size ‘5’ and 100 times
larger than a size ‘4’.
The Haiti Earthquake measured 7.0 on the Richter Scale!
The Christchurch Earthquake measured 6.3
The earthquake in Japan measured a whopping an 8.9

18. A seismograph

19. Mercalli Scale
The Mercalli scale
measures how much
damage is caused by the
earthquake based on
observations.
It is measured on a scale
between 1 and 12.
Mercalli Scale

20. I Felt by almost no one.
II Felt by very few people.
III Tremor noticed by many, but they often do not realise it is an
earthquake.
IV Felt indoors by many. Feels like a truck has struck the building.
V Felt by everyone; many people are awakened. Swaying trees and
poles may be observed.
VI Felt by all; many people run outdoors. Furniture is moved.
VII Everyone runs outdoors. Poorly built structures considerably damaged.
Slight damage elsewhere.
VIII Specially designed structures damaged slightly, others collapse.
IX All buildings considerably damaged, many shift off foundations.
Noticeable cracks in the ground.
X Many structures destroyed. Ground badly cracked.
XI Almost all structures fall. Bridges wrecked.
XII Total destruction. Waves seen on ground surfaces.

21. Can we Predict an
Earthquake?
YES AND  Seismologists study the activity of
NO!
plate boundaries and the earths
crust in order to gain a better
understanding of when Earthquakes
will occur. Currently they are able to
predict an earthquake within a
decade or so, however this is not
specific to year, month, day or time.

22.  Impacts of an Earthquake?:
Deaths Impact on economy
Injuries Government funding
Destruction of houses Families lose everything and have to
Collapsed buildings like: schools, rebuild their lives
hospitals, aged care, universities, Loss of loved ones
shops, skyscrapers, hotels, fire Food supply is affected
stations, police stations No electricity
Roads are cracked Water supply can become contaminated
Water, sewage and storm pipes are Severe injuries can impact on an
damaged individuals entire life
Electricity and Reception poles/cables Disease outbreak
are damages Not enough resources to treat the sick
Natural habitat and injured
Start to think about these impacts! We will look at this more in the
Socio-Economic Natural Disaster Toolbox!