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EARTHQUAKES AND
VOLCANOES
CHAPTER 18 & 19
ANEarthquakeIS
The sudden shaking and vibrating
of the earths crust caused by
movement of faults
EARTHQUAKE FACTS
▪ There are more than a million earthquakes
a year but only a small amount are
actually felt.
▪ Out of the million earthquakes a year only
about 20 cause damage to buildings and
loss of life.
Focus and Epicenter
▪ Focus- The point beneath the earths surface where rocks break (energy is released)
▪ Epicenter- The area of land directly above the FOCUS. Most violent shaking happens here.
Distribution of Earthquakes
▪ USA Recent Earthquake Map
RING OF FIRE
▪ Ring of fire is the border of the Pacific
Plate.
▪ Results from Pacific plate being subducted
under other plates.
▪ Composed of 75% of the worlds
volcanoes.
Ring of Fire
Seismic Waves
▪ Earthquakes cause
shock waves to travel
through the earth.
Seismic Waves
▪ There are
three types of
seismic
waves
generated
from an
earthquake.
Primary Waves (P-waves)
▪ Are the fastest
waves
▪ Can travel through
solids and liquids
Secondary Waves (S Waves)
▪ Arrive after P
waves
▪ Travels through
solids NOT liquids
and gases.
Surface Waves (L waves)
▪ Move along the
earths surface side
to side
▪ Slowest of all
waves
▪ Cause the most
damage!
▪ Travel through
solids, not liquids
or gases.
Measuring Earthquakes
on the Ocean floor
MEASURING EARTHQUAKES
▪ MAGNITUDE- THE AMOUNT OF
ENERGY RELEASED FROM A
EARTHQUAKE
▪ RICHTER SCALE- A SCALE OF 1-10
BASED ON THE SIZE OF THE WAVES
GENERATED BY AN EARTHQUAKE
Structure of the EarthThe Earth’ interior is
broken up into 4 layers.
1) Crust- Outer layer of the Earth.
2) Mantle- Molten rock layer (magma)
3) Outer Core- semi-solid layer of magma some iron and nickel
4) Core- Solid layer of Iron and Nickel
Formation of a Volcano
▪ Magma - is a mixture of molten rock,
minerals and dissolved gases.
▪ Rocks begin to melt at 800º to 1200°C
▪ Molten rock beneath the earth crust is
called MAGMA when it reaches the
surface it is called LAVA.
MAGMA / LAVA ??
MAGMA / LAVA???
Types of Lava
▪ Pahoehoe- runny lava
Types of Lava
▪ Ah ah (A’a)- resembles rubble.
Composed of broken lava blocks
VOLCANO TYPES
▪ Three types of
volcanoes
▪ Shield
▪ Composite
▪ Cinder cone
Composite Volcano
▪ Made up of a mixture
of lava and cinders
▪ Has a steep top with
a medium base
Shield Volcano
▪ Made up of “runny”lava pahoehoe
resembles a shield
▪ Wide base with a
short top
Cinder Cone Volcano
▪ Made up of cinders
and ash.
▪ Resembles a pile of
rubble
Mount Pinatubo
June 1991
Philippines
What type of volcano???
What type of volcano???
What type of volcano???
What type of volcano???
What type of volcano???
PYROCLASTIC MATERIAL
▪ Volcanic DUST- under
1mm sized particles
▪ Volcanic ASH- 1-2mm
sized particles
▪ Volcanic CINDERS- 3-
8mm sized particles
▪ Volcanic BOMBS- 9
mm and up sized
particles
LAKE NYOS Cameroon
AUGUST 26, 1986 1700 PEOPLE DEAD
3000 LIVESTOCK DEAD
Lake Nyos
LAKE NYOS
Lake NYOS