volcanoes and earthquakes. day 1 objective: objective: – i can explain how a volcano is structured
TRANSCRIPT
Volcanoes and Earthquakes
DAY 1• Objective: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
• ObjectiveObjective: –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: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 P-Wave & 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