Susan Barton

1
Earthquakes
And
Volcanoes

• Susan Barton
• GCMS
• 7B Science

2
Defining Earthquakes

• Shaking and trembling of the earths crust.
• The waves travel in all directions
• More than 1,000,000 occur a year or one every 30
  seconds
• Faulting is the most common cause
• Earthquakes continue until all the energy is used
  up
• TSUNAMIS- earthquake on the ocean floor causing
  waves to become greater than 20 meters high

3
Seismic Waves

• FOCUS- underground point of origin
• EPICENTER- aboveground of origin most violent
  shaking occurs at the epicenter
• The three main types of seismic waves are P
  waves, S waves, and L waves

4
P Waves

• Primary waves
• Arrive first at the epicenter
• Can travel through solids, liquids, and gases
• They are push-pull waves

5
S Waves

• Secondary waves
• Can travel through solids, but NOT through
  liquids and gases
• Move in up-down motion

6
L Waves

• Surface waves
• Slowest moving seismic waves
• Travel on top of Earths surface
• Cause most of damage to Earth, because they bend
  and twist the surface

7
John Milne- 1893

• Seismograph-measures and detects seismic waves
• Seismogram- Paper record of waves
• Seismologist- scientist who study earthquakes
• Richter Scale- a scale that allows scientists to
  determine earthquake strength based on many
  readings
• 1-10 levels at which an earthquake is measured on
  amount of damage caused Above a 6 is very
  destructive

8
VOLCANOES

• Volcano- place on Earths surface that allows
  magma and other material to erupt
• Magma- found beneath the Earths surface, it is
  liquid rock
• Lava- magma that reaches the Earths surface

9
Volcanic Fragments

• Volcanic Dust- less that 0.25 mm in diameter
  (flour)
• Volcanic Ash- more than 0.25 less than 5 mm
  (rice)
• Volcanic Bombs- few cm to several meters.

• Cinders- volcanic bombs the size of golf balls

10
Types of Volcanoes

• Cinder Cones- made of mostly of cinders formed
  from explosive eruptions
• Shield- Made of quiet lava flows
• Composite- made up of alternating layers of rock
  particles explosive eruptions, then quite lava
  flows

11
Volcanic Terminology

• Crater- funnel shaped pit, or depression at top
  of volcano
• Caldera- when a crater becomes too large, it
  collapses also can form when the top of a
  volcano collapses or explodes

• Dormant- sleeping volcano
• Extinct- not known to have erupted in modern
  history
• Active- Erupts fairly regularly

12
Ring of Fire
13
Zones

• There are 3 zones
• Ring of Fire- Extends nearly all the way around
  the edge of the Pacific Ocean
• Mediterranean Sea- Italy, Greece, Turkey
• Iceland and Atlantic Ocean- Mid Atlantic Ridge

14
EXTRA! EXTRA!

• Mount St. Helens is a volcano is Washington State
• San Andreas Fault in California
• New Madrid Fault is where we live