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