Download Volcanoes and Earthquakes

Volcanoes and
Earthquakes
DAY 1
• Objective:
–I can explain how a volcano is
structured
What is a Volcano?
• A mountain
formed of lava
and/or
pyroclastic
material
Anatomy of a Volcano
• Vent
– Opening in the crust
• Crater
– Steep-walled depression at the
top
• Magma Chamber
– Where the molten rock waits
• Magma Tube
– Links the vent to the magma
chamber
Day 2
• Objective:
–I can explain what happens when a
volcano erupts
Magma verse Lava
• Magma
– Molten rock under
the surface of
Earth
• Lava
– Molten rock on the
surface of Earth
Factors Affecting Eruption
• Magma
Composition
• Magma
Temperature
• Amount of
Dissolved Gases
Viscosity of Magma
• Substance’s resistance to
flow
• Hotter the magma, more
fluid and less viscous
• Directly related to its
silica content
– More silica, greater its
viscosity (slower
movement)
Dissolved Gases
• Consist of water
vapor and carbon
dioxide
• More gases, the
more violent the
eruption
• Gases
–70% water vapor
–15% carbon dioxide
–5% nitrogen
–5% sulfur
• Pyroclastic Material
– Fragments ejected
during eruptions
– From very fine to
several tons
– Ex:
• Volcanic Ash
• Cinders (lapilli)
• Volcanic Bombs
Other Eruption Results
• Pyroclastic Flow
– Consist of hot gases,
glowing ash, and large
rock fragments
– Races down the steep
slope
• Lahar
– Mudflow that occurs
when volcanic debris
becomes saturated with
water and rapidly
moves down steep
volcanic slopes
DAY 3
• Objective
– I can describe the locations of volcanoes and
the relationship between volcanoes and plate
tectonics
Plate Tectonics & Volcanoes
• Relationship
– Plate movement
provided the
mechanism by
which mantle
rock melts to
generate magma
Ring of Fire
• Area around the
pacific ocean with
extreme volcanic
activity
• This shows the
Pacific Plate
Boarder
Intraplate Activity
• Occurs with a plate,
not a plate
boundary
• Hot Spots
– Small volcanic
region a few
hundred kilometers
across within a plate
– Ex: Hawaiian
Islands
DAY 4
• Objective:
–I can explain what an earthquake is
–I can explain why earthquakes happen
What is an Earthquake?
• Vibration of
Earth
• Produced by a
sudden release of
energy
• Movement along
a fault line
Parts of an Earthquake
• Focus
– Point within Earth where
the earthquake starts
• Epicenter
– Location on the surface
directly above the focus
• Fault
– Associated with
earthquakes activity where
movement has occurred
Causes of Earthquakes
• Elastic Rebound Hypothesis
– Release of built-up energy
– Most earthquakes are produced by the rapid
release of elastic energy stored in rock that has
been subjected to great forces
– When the strength of the rock exceeded, it
suddenly breaks, causing the vibrations of an
earthquake
Foreshock vs. Aftershock
• Foreshock
– Small earthquakes
before the big
quake
• Aftershock
– Smaller
earthquakes after
the big quake
Seismic Science
• Seismology
– Study of earthquake
waves
• Seismograph
– Instruments that
record earthquakes
• Seismogram
– The record made by
a seismograph
Day 5
• Objective:
–I can explain how to locate origin of an
earthquake
–I can explain how to measure the
strength of an earthquake
Earthquake Waves
• Two Main Types
–Surface Waves
–Body Waves
• P-waves
• S-waves
Surface Waves
• Seismic waves that
travel along Earth’s
outer layer
• Moves up & down
and side to side
• Most destructive
• Last to arrive at the
seismograph
Body Waves
• P-Waves (primary waves)
– They push (compress) and pull
(expand) rocks in the direction
the wave travels
– Can travel through solids,
liquids and gases
– Fastest waves
– First to the seismograph
• S-Waves (secondary waves)
– Shakes particles at right angles
to their travel
– Can only travel through solids
– 2nd to the seismograph
Locating Earthquakes
• The difference in
velocity of a PWave & S-Wave
provides a way to
locate the epicenter
– Use a travel-time
curve graph
– Needs at least three
seismograph station
data
Strength of an Earthquake
• Two different types
of measurements to
describe the
strength of an
earthquake
– Intensity
– Magnitude
Earthquake Intensity
• A measure of the
amount of
earthquake
shaking at a
given location
based on the
amount of
damage
Earthquake Magnitude
• A measure of the
size of seismic
waves or the
amount of energy
released at the
source of an
earthquake
The Richter Scale
• Measures
magnitude
• Based on the
amplitude of the
largest seismic wave
• A TEN-FOLD
system
• Largest earthquake
record= 9.6
(CHILE)
Moment Magnitude Scale
• More precise
• Amount of
displacement that
occurs along a fault
zone
• Most widely used
– Estimates energy
released by
earthquakes
Mercalli Intensity Scale
• How much damage
occurs
• Depends on:
– Strength
– Distance from the
epicenter
– Nature of the
surface material
– Building design
DAY 6
• Objective:
–I can describe the dangers of an
Earthquake
–I can explain how to make earthquake
predictions
Earthquake Hazards
• Seismic Vibrations
– Damage to building
depends on several
factors
• Intensity of vibration
• Duration of vibration
• What type of material
built on
• Design of the structure
• Liquefaction
–Stable soil
turns into a
liquid that is
not able to
support
building or
other
structures
• Tsunami
– Large ocean
wave created by
an earthquake
• Landslides
– Greatest damage to
structures
– Sinking of the ground
triggered by the
vibration
• Fires
– Caused by
ruptured gas
lines
Predicting Earthquakes
• Short Range
– Measure uplift,
subsidence and
strain in the
rocks
– Short-range
predictions have
not been
successful
• Long Range
– Based on the idea
that earthquakes
are repetitive
– Seismic Gap
• An area along a
fault where there
has not been any
earthquake
activity for a long
period of time