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

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

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

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

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

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

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

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

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

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

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

Ring of Fire

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

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