1. Susan Barton GCMS 7B Science
Earthquakes
And
Volcanoes
Susan Barton
GCMS
7B Science

2. Defining Earthquakes Shaking and trembling of the earth’s 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 Earth’s 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 Earth’s surface that allows magma and other material to erupt
Magma- found beneath the Earth’s surface, it is liquid rock
Lava- magma that reaches the Earth’s 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