Download Volcanoes and Earthquakes

Do Now:
• How can or does a volcanic eruption or
earthquake occur? What forces on this
planet are responsible for them?
Explain your answer in complete
sentences.
• T and T
Aim: How do volcanoes and
earthquakes change our
planet?
Volcanoes &
Earthquakes
Unit 2.1b
Volcanoes
• are mountains formed when plates meet
• magma from asthenosphere rises
through the lithosphere to erupt on the
surface as lava
1. if internal pressure is high
enough…
• Lava, ash, and gases can be ejected
into the atmosphere or flow over land
Extinct volcanoes
Eruption cloud
Ash flow
Ash
Acid rain
Lava flow
Mud flow
Landslide
Central
vent
Magma
conduit
Magma
reservoir
Fig. 14-6b, p. 351
2. Volcanic Activity
• Active volcano- has/can erupt
– Magma has a direct line to the volcano and
pressure exists within the volcano
• Dormant volcano- not known to erupt
– Moving plates can connect magma to it
activating it
• Extinct volcano- wont erupt again
– Magma line cut off due to moving plates
Volcano leading to islands
3. Types of volcanoes
• Rift volcano- when plates move away from
each other and magma creates new ocean
crust
• Subduction volcano- when plates collide and
slide over each other exposing magma
• Hot spot volcano- place within a plate where
magma upwelling causes magma to rise to
the surface
– not at plate boundaries
– Ex: Hawaiian Islands
F. Earthquakes (EQ)
• Result of vibrations deep in the earth that
release energy
– Usually at transform boundaries where plates
grind past each other and friction builds up
when they get stuck in one spot until the point
where they slip past each other releasing all
the energy from the friction being released
• Focus- where the EQ begins inside Earth
• Epicenter- where the EQ reaches surface
Major Features and Effects of
an Earthquake
Fig. 14-7, p. 351
Liquefaction of recent
sediments causes
buildings to sink
Landslides
may occur on
hilly ground
Two adjoining plates
move laterally along
the fault line
Earth movements
cause flooding in
low-lying areas
Shock
waves
Epicenter
Focus
Fig. 14-7a, p. 351
1. Measuring EQ
• Seismograph- measures size (magnitude)
of EQ
• Richter Scale- measures the amplitude of
the highest S-wave of an EQ
– Each # = 33x the energy compared to the
previous #
Earthquakes Are Geological
Rock-and-Roll Events (2)
• Richter scale
–
–
–
–
–
–
Insignificant: <4.0
Minor: 4.0–4.9
Damaging: 5.0–5.9
Destructive: 6.0–6.9
Major: 7.0–7.9
Great: >8.0
• Largest recorded earthquake: 9.5 in Chile in 1960
2. Major EQ features
Earthquake Risk in the United
States
Figure 16, Supplement 8
3. Global EQ Risk
Earthquakes on the Ocean Floor Can
Cause Huge Waves Called
Tsunamis
• Tsunami, tidal wave
– Travels several hundred miles per hour
• Detection of tsunamis
– Buoys in open ocean
• December 2004: Indian Ocean tsunami
– Magnitude 9.15 and 31-meter waves at shore
– Role of coral reefs and mangrove forests in
reducing death toll
4. EQ Effect: Tsunami Formation
Ex: Indonesia Tsunami 2004
• In December 2004, a great EQ with a
magnitude of 9.15 on the seafloor of the
Pacific Ocean created a large tsunami
that killed 168,000 people in Indonesia.
Indonesia shoreline
June 23, 2004 before tsunami
December 28, 2004
aftermath from the tsunami
Shore near Gleebruk in Indonesia
before and after the Tsunami on
June 23, 2004
Fig. 14-9, p. 353
Summary:
• How do volcanoes and earthquakes
impact society?