volcanoes and earthquakes...during earthquakes, energy is released as waves earthquake waves...
TRANSCRIPT
Volcanoes and Earthquakes
Questions 1. What is an earthquake? 2. What is a volcano 3. In what state are earthquakes most likely to occur? Justify your
answer 4. In what state are volcanoes most likely to occur? Justify your
answer. 5. In what country are earthquakes most likely to occur? Justify
your answer. 6. In what country are volcanoes most likely to occur? Justify your
answer. 7. Compare the three types of volcanoes. 8. Compare the three types of seismic waves 9. Explain how an earthquake is located. 10. What can the locations of earthquakes and volcanoes tell us
about the Earth?
What Is an Earthquake?
• Focus - point within Earth where earthquake starts.
• Epicenter - location on
the surface directly
above the focus
Earthquake - vibration of Earth caused by rapid release of energy
Focus and Epicenter
• Faults - fractures in
Earth where movement
has occurred.
Faults
Causes of Earthquakes
Elastic Rebound Hypothesis - Rapid
release of elastic energy stored in rock
that occurs when rock is broken
Earthquake Waves
Surface waves - travel along Earth’s outer layer
P waves
• Push-pull waves that compress and expand in the direction that the
waves travel
• Travel through solids, liquids, and gases
• Fastest of all earthquake waves
S waves
• Travel along Earth’s outer layer
• Shake particles at right angles to the direction of travel
• Travel only through solids
• Slower than P waves
During earthquakes, energy is released as waves
Earthquake Waves
Seismographs and Seismograms
Seismographs are instruments that
record earthquake waves
Seismograms are traces of amplified,
electronically recorded ground motion
made by seismographs
A seismogram shows all three
types of seismic waves—
surface waves, P waves, and
S waves
Locating Earthquakes
Earthquake Distance - The epicenter
is located using the difference in the
arrival times between P and S wave
recordings, which are related to
distance
.
Locating Earthquakes
.
Earthquake Direction - Travel-time graphs from three or more
seismographs can be used to find the exact
location of an earthquake epicenter
Locating Earthquakes
.
Earthquake Zones - About 95 percent of the major earthquakes occur
in a few narrow zones
Measuring Earthquake Intensity
Indirect Effects of Earthquakes
• Ground Tilting
• Differential Settlement
• Liquefaction
• Tsunamis
• Landslides
• Floods
• Fires
Introduction to Volcanoes
Volcano - Mountain formed from lava and/or ash
and other material ejected during an eruption
Factors Affecting Eruptions
Viscosity – Resistance to flow
• Composition of the magma
• Temperature of the magma
Higher the temperature, less
viscous the lava
Higher the silica, more viscous
• Which is more viscous – water or maple syrup
• Greater the viscosity, slower the flow
• What affects viscosity?
Factors Affecting Eruptions
Dissolved Gases
• Water Vapor and Carbon Dioxide
• Provides force to send lava through vent (hole
in Earth’s crust)
Violence of Eruptions
Viscosity
• Viscous magma = violent eruption
• Fluid magma = gentle eruption
Gas Content
• Lots of gas = violent eruption
• Little gas = gentle eruption
Types of Volcano
Shield
• Large, broad, gently sloping
• Accumulation of lava
• Oceans/Island
Types of Volcano
Cinder Cones
• Small and steep
• Ash and rock
• Occur in groups
Types of Volcanoes
Composite Cones
• Large and very violent
• Lava flows and rock and ash
• Generally adjacent to Pacific Ocean
Profiles of Volcanic Landforms
